Dual Port AX99100 RS-232 Card
4.5Editor score
Two RS-232 DB9 ports
256-byte transmit FIFO
Multiple PCIe slot widths
Windows and Linux support
In this guide
A Pcie Serial Port Card adds legacy RS-232 and DB9 connectivity to a modern computer, making it useful for scanners, industrial controls, point-of-sale systems, printers, security equipment, and specialized laboratory devices. The right card depends on port count, operating system, chassis clearance, supported serial specifications, and the equipment that must be connected.
We compared the ten featured cards by examining their documented port configurations, UART chipsets, maximum data rates, operating-system support, installation requirements, bracket options, and intended applications. The list includes single-port and dual-port designs from general-purpose vendors and TAA-oriented models, giving both basic users and industrial-system buyers relevant choices.
Each review explains the strongest reason to consider the card, along with practical limitations and installation considerations. The first three recommendations cover the most compelling combinations of features, while the remaining entries serve narrower requirements. Product availability, configurations, and prices can change, so verify the current listing and your equipment requirements before purchasing.
Top 3 Picks for Best Pcie Serial Port Card
PCIE-SE2 Dual RS-232 Card
4.5Editor score
Two independent DB9 ports
ASIX AX99100 UART
Full and low-profile brackets
Broad Windows compatibility
StarTech PEX2S953LP
4.9Editor score
Two configurable RS-232 ports
Up to 921.6Kbps per port
16950 UART with FIFO
TAA-compliant StarTech design
Top 10 Best Pcie Serial Port Card in 2026 Compared
The comparison below organizes every featured card by port count, serial controller, stated operating-system support, and installation format, making it easier to identify the model that matches your computer and connected equipment.
ProductsSpecificationsEditor scorePrice
Editor's Choice
PCIE-SE2 Dual RS-232
Two RS-232 DB9 ports
ASIX AX99100 controller
Windows XP through 11
Full and low-profile brackets
4.5Editor score
Editor's Choice
StarTech PEX1S953LP
One RS-232 DB9 port
ASIX AX99100 controller
Up to 921.6Kbps
Windows and Linux support
4.2Editor score
Best Budget
Dual Port AX99100 Card
Two RS-232 DB9 ports
ASIX AX99100 controller
256-byte transmit FIFO
Full and low-profile brackets
4.5Editor score
StarTech PEX2S953LP
Two RS-232 DB9 ports
16950 AX99100 UART
Up to 921.6Kbps
Individually configurable pin 9
4.9Editor score
StarTech PEX2S1050
Two DB9 serial ports
PCI Express 1.0a
Up to 460Kbps
Plug-and-play IRQ sharing
4.2Editor score
WCH382 Combo Card
Serial and parallel ports
WCH382 controller
Parallel rate up to 1.5Mbps
PCIe x1 interface
4.3Editor score
AX99100 Dual Serial Card
Two RS-232 DB9 ports
ASIX AX99100 controller
256-byte transmit FIFO
Two low-profile brackets
3.7Editor score
VANTEC Dual Serial Card
Two RS-232 serial ports
PCI Express host card
Legacy connectivity design
Check configuration before purchase
5.0Editor score
WCH382 Dual Serial Card
Two RS-232 DB9 ports
Dual 16C550 UART
Up to 230400Bps
Low-profile bracket included
4.2Editor score
MCS9922 Single Serial Card
One RS-232 DB9 port
MCS9922 controller
Up to 250Kbps
256-byte transmit FIFO
4.3Editor score
1. PCIE-SE2 Dual RS-232 – Best Overall Expansion Option
PCIE-SE2 Dual RS-232
Two independent DB9 ports
ASIX AX99100 controller
256-byte transmit FIFO
Multiple PCIe slot widths
The PCIE-SE2 is a well-balanced two-port expansion card for adding RS-232 connectivity to a desktop or industrial PC. Its 4.5 rating reflects a generally favorable user history, while the documented use of the ASIX AX99100 solution gives it a recognizable technical foundation. The card is especially useful when one legacy device is not enough and both scanners, terminals, or controllers need dedicated DB9 connections.
Pros
- Two ports support multiple devices
- Works across many Windows versions
- Includes standard and low-profile brackets
- Supports common legacy applications
- Compatible with several CPU platforms
Cons
- Requires driver installation
- Linux setup may require compilation
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Two independent ports provide more flexibility than a single-port card without requiring a larger multi-I/O design. The AX99100-based controller includes a 256-byte transmit FIFO, while the product supports Intel, AMD, and ARM hardware platforms. Compatibility extends across Windows XP, Vista, 7, 8.x, 10, and 11 in both 32-bit and 64-bit configurations, with Linux source code provided for listed kernel series.
The main drawback is that setup is not entirely plug-and-play: desktop users must install the appropriate driver from the included mini-CD. Linux users may also need to compile the supplied source rather than relying on automatic recognition. In addition, slim systems require manual bracket changes. These are installation considerations rather than fundamental functional limitations, but they make the card less convenient for users who expect a completely effortless setup.
This is the strongest general recommendation for buyers who need two serial ports, a long list of operating-system versions, and support for common industrial or POS devices. Choose it when you have a free PCIe slot and can complete the specified driver installation. It is less suitable for a single basic serial peripheral, where a one-port card would be simpler.
Useful Port Flexibility
Two ports let you connect multiple RS-232 devices at once, reducing the need for an external adapter or additional expansion card. The stated application range includes POS systems, scanners, printers, security systems, and industrial testing equipment.
Flexible Chassis Fit
A full-size bracket covers standard desktop cases, while the supplied low-profile alternative supports slim systems. The x1 interface also fits compatible x4, x8, and x16 physical slots, which simplifies installation in many modern PCs.
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2. StarTech PEX1S953LP – Best Single-Port TAA Option
StarTech PEX1S953LP
One RS-232 DB9 port
ASIX AX99100 controller
Up to 921.6Kbps
Configurable pin 9 power
The StarTech PEX1S953LP is a focused one-port solution for systems that need a single high-speed RS-232 connection. Its 4.2 rating indicates a solid but not universally perfect customer record. The card is built around the ASIX AX99100 and a 16950 UART, making it suitable for specialized equipment rather than ordinary modern peripherals.
Pros
- High documented transfer rate
- TAA-oriented StarTech model
- Includes both bracket styles
- Configurable external power
- Supports Windows and Linux
Cons
- Only one serial port
- Pin 9 power needs configuration
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The stated maximum rate of 921.6Kbps per port is a major advantage when transferring larger data volumes over serial. A 256-byte FIFO and support for the ninth data bit add useful control for industrial, laboratory, and POS environments. Pin 9 can be configured for 12V, 5V, or no power, offering compatibility with connected devices that use externally powered serial signals.
Because it has only one DB9 port, the card cannot directly serve two serial peripherals. It also does not include the multiport convenience of the dual-port StarTech PEX2S953LP. The configurable-power feature is valuable when needed but introduces another installation consideration: installers should confirm the electrical requirements of the connected equipment before choosing a pin 9 setting.
Buyers in government, institutional, or managed procurement environments may find the TAA designation particularly relevant. It is also a good fit for technicians who need one dependable port, a high documented transfer rate, and a simple desktop or server installation. Choose the single-port model only if your equipment plan truly requires just one RS-232 connection.
Serious Serial Throughput
The 921.6Kbps maximum rate gives this card an advantage for data-heavy instruments compared with cards limited to 230,400Bps, 250Kbps, or 460Kbps. The 16950 UART also supports the ninth data bit and a 256-byte FIFO.
Managed Installation Support
The TAA-oriented model is relevant for institutional purchasing requirements. Including both standard and low-profile brackets makes it easier to fit the card across different desktop and server chassis.
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3. Dual Port AX99100 Card – Best Value for Two Ports
Dual Port AX99100 Card
Two independent RS-232 ports
ASIX AX99100 controller
256-byte transmit FIFO
Windows and Linux support
This dual-port card delivers a useful combination of features at a notably accessible price point, which is why it earns the Best Budget designation. It carries a 4.5 rating and uses the same ASIX AX99100 controller family seen in more specialized options. Buyers get two independent RS-232 DB9 ports without moving to a larger or costlier host adapter.
Pros
- Attractive two-port configuration
- Recognizable AX99100 controller
- Broad legacy Windows support
- Fits several PCIe slot widths
- Includes low-profile bracket
Cons
- Driver installation required
- Linux source compilation may be needed
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The controller's 256-byte transmit FIFO and support for Intel, AMD, and ARM platforms make it broadly adaptable. Listed operating-system support includes Windows XP through Windows 11 in 32-bit and 64-bit forms, plus source code for Linux kernels 2.6.x through 5.x. Its full-size and low-profile brackets and compatibility with x1, x4, x8, and x16 slots simplify physical installation.
As with the PCIE-SE2, this is not a no-instructions card. The supplied mini-CD contains the drivers required for desktop systems, and Linux users may have to compile the included source code. A 2U system also requires manually replacing the full-size bracket. Users who are comfortable with basic expansion-card installation should find these steps manageable.
This is the best-value option for a small business, repair technician, or home lab that needs two serial connections and supports older Windows systems. It is particularly sensible when the goal is dependable port count and broad platform support rather than specialized pin 9 power or a maximum rate of 921.6Kbps. Check the Linux driver process before purchasing if that operating system is essential.
More Ports Per Purchase
Two independent ports provide better value for installers than a single-port card when several DB9 devices are involved. Each connection can serve a separate scanner, terminal, controller, or other RS-232 device.
Legacy System Coverage
Support for older and newer Windows releases makes the card useful for refurbishing established equipment. The 32-bit and 64-bit coverage is particularly helpful for mixed-architecture business environments.
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4. StarTech PEX2S953LP – Best Premium Dual-Port Card
StarTech PEX2S953LP
Two configurable RS-232 ports
16950 AX99100 UART
Up to 921.6Kbps
Individually configurable pin 9
The StarTech PEX2S953LP is the strongest all-around premium recommendation in this group, supported by a 4.9 rating. It combines two DB9 ports, a 16950 UART based on the ASIX AX99100, and a maximum rate of 921.6Kbps per port. Those characteristics make it well suited to professional POS, factory automation, laboratory, medical-equipment, and service applications.
Pros
- Highest rating in the selection
- Two high-speed serial ports
- Independent pin 9 configuration
- Both bracket styles included
- TAA-compliant product line
Cons
- Premium-oriented brand and model
- Windows XP and Linux support stated
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Each port can be individually configured for 12V, 5V, or no power through pin 9, with up to 2A total. This is a meaningful feature when connected equipment requires a particular handshake or power arrangement. The 256-byte FIFO and ninth-data-bit support further distinguish it from simpler cards. Both low-profile and full-profile brackets are included, and the card supports Windows XP and later as well as Linux.
Its main tradeoff is straightforward: this premium positioning comes with a higher cost than budget-oriented alternatives. The information also does not emphasize a 256-byte transmit FIFO separately because the 16950 UART specification already identifies the buffer arrangement. As always with pin 9 power, the attached device's requirements must be verified before changing the configuration.
This card is ideal for professional integrators who need two fast ports, independent configuration, and broad operating-system support. It also fits organizations that value the TAA-oriented StarTech product line. For a technician connecting one ordinary serial printer, the feature set is more than necessary; for a multi-device installation, it provides meaningful control and reliability.
Independent Port Configuration
Each DB9 port can receive its own pin 9 power setting, allowing different devices to use different signal arrangements. This is helpful in mixed installations that would not benefit from a one-size-fits-all configuration.
Professional Throughput
A 921.6Kbps maximum rate per port supports demanding serial workflows. The 16950 UART, 256-byte FIFO, and ninth-data-bit capability also make the model a stronger fit for specialized instrumentation.
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5. StarTech PEX2S1050 – Best Established-TAA Alternative
StarTech PEX2S1050
Two DB9 serial ports
PCI Express 1.0a
Up to 460Kbps
Plug-and-play IRQ sharing
The StarTech PEX2S1050 is a straightforward dual-port card with a 4.2 rating and a strong emphasis on simple installation. It complies with PCI Express 1.0a and fits x1, x2, x4, x8, and x16 slots, giving it broad physical compatibility. It is a practical choice for manufacturing equipment, POS systems, and security devices in established Windows-based environments.
Pros
- Simple plug-and-play installation
- Automatic IRQ and address selection
- Fits all common PCIe widths
- TAA-oriented established model
- Includes low-profile bracket
Cons
- Lower maximum rate than AX99100 models
- Primarily presented for Windows compatibility
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Automatic IRQ and I/O address selection, IRQ sharing, and plug-and-play connection reduce configuration work. The card supports transfer rates up to 460Kbps, which remains practical for many control and transaction systems. A standard-profile bracket is installed, and an optional low-profile bracket is included for compact chassis.
Compared with the ASIX AX99100-based StarTech cards, the maximum transfer rate is lower, and the product information focuses on Windows compatibility rather than presenting the same broad Windows-and-Linux matrix. Users requiring the latest 16950 features, 921.6Kbps throughput, or configurable pin 9 power should examine the newer PEX1S953LP or PEX2S953LP instead.
This card is a good option for managed IT environments that value a TAA-oriented product, automatic resource assignment, and straightforward deployment. It is especially suitable when 460Kbps is more than sufficient and two serial peripherals need to be connected to a single PC. Verify operating-system requirements against the included documentation before installing it in a Linux or mixed-platform fleet.
Minimal Configuration Effort
Automatic IRQ and I/O address selection remove much of the manual tuning associated with older serial expansion hardware. IRQ sharing also helps the card coexist with other devices in a busy system.
Broad Physical Compatibility
Support for x1 through x16 physical slots makes the card adaptable across many desktop and server designs. The included low-profile bracket expands its usefulness in compact systems.
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6. WCH382 Combo Card – Best for Serial and Parallel
WCH382 Combo Card
Serial and parallel ports
WCH382 controller
Parallel rate up to 1.5Mbps
PCIe x1 interface
The WCH382 combo card is the choice for legacy installations that need both serial and parallel connectivity. Its 4.3 rating reflects a generally positive reception, and its distinguishing feature is clear: a PCIe x1 card with an RS-232 connection and an IEEE 1284 printer port. That combination is valuable for older point-of-sale peripherals, specialized printers, and equipment that has not transitioned fully to USB.
Pros
- Adds both serial and parallel
- Multiple IEEE 1284 modes
- Automatic IRQ and address selection
- Supports broad operating systems
- Includes low-profile bracket
Cons
- Requires CH38XDRV driver installation
- Less focused on serial-only needs
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The parallel controller supports SPP, PS2, EPP, and ECP modes with rates up to 1.5Mbps. The card automatically selects IRQ and I/O address, supports IRQ sharing, and is described as plug-and-play after its driver is installed. Listed operating-system support covers older 32-bit Windows systems, newer 64-bit Windows releases through Windows 11, and Linux.
Installation requires opening the CH38XDRV file on the included CD, so buyers who need a truly driverless experience may prefer a card with more explicit automatic setup. It also offers only one serial connection and may be unnecessary for a computer that already has a parallel printer but needs several DB9 ports. The combination is useful only when both connector types are genuinely required.
Choose this card for an upgrade involving a legacy parallel printer plus one serial peripheral, especially in an older industrial or retail environment. Its multiple parallel modes and broad OS list are strong selling points. If your needs are exclusively RS-232, a dedicated dual- or single-port card will provide a simpler and more focused solution.
One Card, Two Legacy Interfaces
Combining RS-232 and IEEE 1284 in one expansion card reduces the need for separate PCI slots and adapters. It is especially useful when both port types are unavoidable parts of an existing device fleet.
Flexible Printer Modes
SPP, PS2, EPP, and ECP support allows the parallel section to work with different legacy printer configurations. The stated parallel transfer rate reaches 1.5Mbps for compatible equipment.
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7. AX99100 Dual Serial Card – Flexible Slim-System Option
AX99100 Dual Serial Card
Two RS-232 DB9 ports
ASIX AX99100 controller
256-byte transmit FIFO
Two low-profile brackets
This AX99100-based card offers two RS-232 ports, broad platform support, and several low-profile bracket options. Its 3.7 rating is the lowest in the selection, so it should not be presented as a universal favorite. However, the documented specifications remain useful for buyers whose main requirements are dual-port connectivity and installation in a slim computer.
Pros
- Two independent serial connections
- Multiple low-profile bracket options
- Recognizable AX99100 controller
- Broad Windows and Linux support
- Fits several PCIe slot widths
Cons
- Lowest rating among featured cards
- Driver installation remains necessary
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The ASIX AX99100 solution includes a 256-byte deep transmit FIFO and supports Intel, AMD, and ARM platforms. Windows XP, Vista, 7, 8.x, 10, and 11 are listed in 32-bit and 64-bit versions, while Linux source code is available for kernels 2.6.x through 5.x. The card works through a PCIe x1 interface and is also compatible with x4, x8, and x16 slots.
The standout installation detail is the inclusion of two low-profile brackets alongside the standard full-size bracket. That can make a difference in slim PCs where exact bracket clearance and mounting geometry are difficult. Against that benefit, the lower rating suggests that some buyers may have encountered installation or support issues, although the provided data does not identify specific complaints.
This model makes the most sense for a technician who has confirmed the system requires one of the included low-profile brackets and values the dual-port AX99100 platform. It is not the first choice for a managed institution, a single-port task, or a user who needs the strongest customer rating. As with other driver-based cards, check the current operating-system requirements before installation.
Bracket Options for Tight Cases
Two low-profile brackets provide useful choice for slim systems with different mounting layouts. The full-size bracket remains available for ordinary desktop installations.
Established Controller Platform
The ASIX AX99100 is a widely referenced controller family in this product category. Its 256-byte transmit FIFO and multi-platform support make the card suitable for established desktop fleets.
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8. VANTEC Dual Serial Card – Straightforward Two-Port Expansion
VANTEC Dual Serial Card
Two RS-232 serial ports
PCI Express host card
Legacy equipment connectivity
Simple two-port configuration
The VANTEC 2-Port Serial RS-232 PCIE Host Card offers the simplest feature proposition in the group: two serial ports for adding RS-232 connectivity to a PCI Express computer. It holds a 5.0 rating, the highest customer score among the featured products. That makes it an attractive option for a simple two-port use case, although the limited supplied information calls for some buyer caution.
Pros
- Perfect five-star user rating
- Two-port serial configuration
- Simple expansion-card format
- Suitable for legacy RS-232 equipment
Cons
- Limited published specification detail
- Verify drivers and bracket inclusion
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The product data confirms the VANTEC brand, two-port RS-232 configuration, and PCI Express host-card format. It does not specify a chipset, maximum transfer rate, FIFO depth, operating-system versions, or bracket configuration. As a result, it should be evaluated as a straightforward connectivity card rather than one with a clearly documented set of advanced UART or power-management features.
The lack of detailed specifications is the primary trade-off. Buyers should confirm driver support, the included full-size or low-profile bracket, maximum baud rate, and exact operating-system compatibility before ordering. They should also verify whether their connected equipment requires pin 9 power or other advanced signaling that is not described for this card.
The VANTEC model is a sensible candidate for users who need two RS-232 ports, see strong customer satisfaction, and do not require documented high-speed or specialized controller functions. It can be a good fit for legacy equipment, maintenance work, and general-purpose serial expansion. For a regulated purchase where procurement requires exact TAA, OS, or electrical specifications, a more fully documented card may be easier to justify.
Strong Customer Feedback
A 5.0 rating is an encouraging signal for buyers who prioritize established customer satisfaction. It suggests the basic proposition of adding two serial ports has resonated well with users.
Verify Before Specialized Use
The short specification set does not explain advanced UART, pin 9, or driver details. Industrial, laboratory, and medical buyers should confirm those requirements directly with the manufacturer or current documentation.
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9. WCH382 Dual Serial Card – Best Industrial UART Alternative
WCH382 Dual Serial Card
Two RS-232 DB9 ports
Dual 16C550 UART
Up to 230400Bps
Low-profile bracket included
The WCH382 dual serial card combines two 16C550 UART ports with a PCI Express host interface and a 4.2 rating. It is a practical alternative for industrial equipment that uses conventional RS-232 DB9 connections. The design is focused on dependable legacy functionality rather than the highest possible serial rate, making it most appropriate when compatibility matters more than extreme throughput.
Pros
- Two independent 16C550 ports
- Industrial-style DB9 connectors
- Automatic resource configuration
- Broad Windows and Linux support
- Low-profile bracket included
Cons
- Lower speed than newer controllers
- Requires CH38XDRV installation
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Each port supports transfer rates up to 230400Bps. The card automatically selects IRQ and I/O address, supports IRQ sharing, and uses a one-lane PCI Express interface. The stated operating-system coverage includes both 32-bit and 64-bit versions across older and newer Windows releases, plus Linux. A low-profile bracket is included, improving its usefulness in compact systems.
Its main limitation is speed. Cards based on the ASIX AX99100 can reach substantially higher documented rates, and the 921.6Kbps StarTech models are preferable for data-heavy instruments. The CH38XDRV file on the included CD must also be opened to install the required software, so setup is not entirely automatic. These constraints matter for high-bandwidth or unattended managed deployments.
Choose this model for a two-device RS-232 installation involving industrial controllers, scanners, or other equipment that operates within 230400Bps. It is also a good option when a low-profile bracket is already part of the system plan. For faster instruments, extensive administration, or TAA procurement, a 16950-based StarTech card offers a more advanced specification sheet.
Recognizable 16C550 Design
The dual 16C550 UART configuration is a familiar serial architecture for industrial and embedded systems. It provides a practical migration path for equipment built around standard RS-232 behavior.
Automatic Resource Handling
Automatic IRQ and I/O address selection simplifies integration. IRQ sharing improves the likelihood that the card can operate alongside other expansion hardware in a conventional desktop.
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10. MCS9922 Single Serial Card – Best Compact Single-Port Choice
MCS9922 Single Serial Card
One RS-232 DB9 port
MCS9922 controller
Up to 250Kbps
256-byte transmit FIFO
The MCS9922 single-port card is a compact solution for adding one RS-232 DB9 connection to a PCI Express system. It has a 4.3 rating and uses the MCS9922 chipset, offering a 256-byte transmit FIFO and support for hardware and software flow control. Its compact low-profile format is particularly useful when only one legacy port is required.
Pros
- Compact single-port design
- Low-profile form factor
- 256-byte transmit FIFO
- Hardware and software flow control
- Supports multiple data formats
Cons
- Only one serial connection
- Modest maximum transfer rate
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The card supports serial formats of 5, 6, 7, and 8 bits and transfer rates up to 250Kbps. Its single-lane PCI Express interface provides throughput up to 2.5Gbps, and the design is compliant with PCI Express Base Specification Revision 1.0a. Those figures concern the host interface, while the actual serial-device performance is governed by the stated 250Kbps UART rate.
The central limitation is that only one peripheral can be connected at a time. Its 250Kbps ceiling is also below the 460Kbps offered by the PEX2S1050 and the 921.6Kbps offered by the newer StarTech AX99100 models. For a printer, basic controller, or point-of-sale device that does not require high throughput, those faster capabilities may be unnecessary.
Choose the MCS9922 when space, simplicity, and one-port functionality matter more than multi-device expansion. It is a sensible fit for maintenance PCs, legacy kiosks, and compact systems needing one conventional serial port. Buyers should still confirm operating-system support, driver availability, bracket requirements, and pin 9 expectations in the current documentation before installation.
Compact for Constrained Systems
The low-profile form factor helps the card fit systems where a full-height serial bracket would be inconvenient. One DB9 port keeps the design focused and uncomplicated.
Flexible Flow Control
Support for both hardware and software flow control gives integrators options when communicating with older or more demanding serial equipment. Multiple character widths broaden device-format compatibility.
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Buying Guide – How to Choose the Best Pcie Serial Port Card
Selecting a PCIe serial expansion card is mostly an exercise in matching physical hardware and documented controller capabilities to the devices you need to operate. Consider port count, serial speed, protocol expectations, operating system, chassis clearance, and driver requirements before choosing a model.
Number of Serial Ports
Begin by counting the RS-232 devices that must operate at the same time. A one-port card is simpler and potentially less expensive, but it cannot connect multiple peripherals without an additional adapter. Two-port cards are the most versatile option in this selection because they can serve separate scanners, terminals, printers, or controllers without requiring a second expansion slot. Ensure that each device uses the standard DB9 connector and that no additional port-sharing hardware is necessary.
Choose one port for a single basic device and two ports for a multi-device workstation. The PEX1S953LP and MCS9922 serve the first need, while the PCIE-SE2, PEX2S953LP, PEX2S1050, WCH382 cards, AX99100 models, and VANTEC card serve the second.
UART and Transfer Speed
The UART generation and maximum baud rate determine how quickly the card can exchange data with connected equipment. The MCS9922 and WCH382 designs are documented at 250Kbps and 230400Bps respectively, while the PEX2S1050 supports up to 460Kbps. The ASIX AX99100-based StarTech models reach up to 921.6Kbps and use a 16950 UART with a 256-byte FIFO, making them stronger choices for data-heavy instruments or industrial equipment.
Match speed to the actual device. A higher rate does not help if the peripheral or cable is limited. For specialized serial work, also verify FIFO depth, ninth-data-bit support, and flow-control requirements before purchasing.
Operating-System Support
A card's electrical design is only one part of usability. Windows XP through Windows 11 coverage appears on several models, including 32-bit and 64-bit editions, and Linux support is also common. Some listings provide source code for Linux kernels 2.6.x through 5.x rather than guaranteeing a fully automatic install. The combo card, dual WCH382 card, and MCS9922 list Linux support but provide fewer Windows-version details in the supplied information.
Check the exact operating-system version, architecture, and driver method for your machine. Do not assume that a card advertised as Windows-compatible will automatically recognize your preferred Linux distribution. Review current documentation before closing a business or industrial purchase.
Chassis and Bracket Fit
PCIe slot availability does not guarantee that the card's external bracket will fit. Standard desktops usually use the full-size bracket, while small-form-factor, slim, and 2U systems may require a low-profile alternative. Several AX99100 cards include both forms, with some providing two low-profile brackets for differing mounting arrangements. The StarTech PEX1S953LP and PEX2S953LP also include standard and low-profile brackets, as does the PEX2S1050.
Measure the available case clearance and inspect the rear panel before ordering. Remember that a low-profile card may still require a physical replacement of the bracket, and compact systems may also have limited space for adjacent cards.
Serial Signal Requirements
RS-232 cards can differ in how pin 9 is handled. The StarTech PEX1S953LP can provide 12V, 5V, or no power through pin 9, while the PEX2S953LP configures each of its two ports independently with up to 2A total. These features can be essential for certain POS terminals or serial devices that use the control line for power or hardware handshaking. Other cards do not provide equivalent details, so their suitability depends on the attached equipment.
Consult the manual for the DB9 serial peripheral and identify its voltage, handshake, flow-control, and pin 9 requirements. Do not apply external power unless the connected device and card documentation both explicitly permit it.
Application and Procurement Needs
General office use, factory automation, laboratory instrumentation, and institutional procurement do not have identical priorities. A general desktop may need only one basic DB9 port, while a factory technician may need dual high-speed ports and robust system documentation. TAA-oriented StarTech products can be more appropriate for managed or government purchasing environments. The combo card stands apart for unusual requirements involving both RS-232 and an IEEE 1284 parallel printer.
List every attached device, its connector, signaling requirements, and operating system before choosing. For regulated or business-critical installations, favor a product with the clearest specifications and suitable procurement credentials.
Driver and Installation Process
Driver requirements can determine whether a card suits a managed environment. The PCIE-SE2 and several AX99100-based options use mini-CD drivers, and Linux users may need to compile source code. The WCH382 products require opening the CH38XDRV file from their CD. By comparison, the PEX2S1050 emphasizes plug-and-play behavior, automatic IRQ and I/O address selection, and IRQ sharing. The VANTEC listing provides too little installation detail to assume automatic operation.
Prefer a documented, repeatable setup process for business deployments. Confirm that the driver source is available for your chosen platform and that the card's resource-management behavior fits your maintenance workflow.
How to Use and Care for Your Pcie Serial Port Card
Before installation, shut down the computer, disconnect its power, and open the case according to the manufacturer's instructions. Confirm that the system has an available PCI Express slot and that the card's bracket matches the chassis. Compare the device's DB9 pinout, voltage requirements, and communication settings with the documentation supplied for the card and connected peripheral. Never hot-plug a serial expansion card unless both the card and system explicitly support that procedure.
Install the card in the appropriate slot, secure the bracket, and reconnect the equipment with powered-off devices whenever possible. Install the specified operating-system driver after the hardware is seated. On Linux, use the provided source code and the manufacturer's instructions rather than assuming automatic recognition. Once the operating system assigns COM or serial device identifiers, configure the application with the baud rate, parity, data bits, stop bits, and flow control required by the attached equipment.
For routine care, keep connectors clean and dry, avoid forcing DB9 plugs, and inspect cables for damaged strain relief. Do not hot-plug a serial peripheral unless its manual explicitly permits it, because voltage transients can damage the UART. If communication is unstable, check the cable, grounding, port settings, and device power requirements before changing drivers or purchasing another card. Keep the included driver media and documentation with the system for future maintenance.
Frequently Asked Questions
What is a PCIe RS-232 serial port card?
A PCIe RS-232 serial port card is an expansion card that adds one or more DB9 serial connections to a computer with a PCI Express slot. It is commonly used to connect legacy or industrial devices such as scanners, POS terminals, printers, PLCs, laboratory instruments, and security equipment. The card translates between the computer's PCI Express interface and the devices' RS-232 signals.
Can I use a PCIe serial card in a modern desktop?
Usually, yes, provided the desktop has an available PCI Express slot and compatible drivers. Most modern desktops have at least one PCIe slot, and many cards using an x1 interface can also physically fit x4, x8, or x16 slots. Check the card's stated operating-system support, especially if your desktop uses an uncommon Linux distribution or a system version outside the listed range.
Do I need a low-profile bracket?
You need a low-profile bracket if the computer case has limited rear clearance, which is common in slim desktops, compact office PCs, and some 2U servers. Standard desktop cases usually work with the full-size bracket. Several featured cards include both, but some require you to remove and replace the bracket manually, so inspect the case before ordering.
Are all PCIe serial cards compatible with Windows 11?
No. Compatibility depends on the specific card, driver, and Windows architecture. Several AX99100-based products explicitly list Windows 11 in both 32-bit and 64-bit versions, while other listings provide a broader or less detailed system matrix. Confirm the current driver and product documentation rather than assuming that PCIe slot compatibility automatically guarantees operating-system support.
What is the difference between one-port and two-port cards?
A one-port card adds a single DB9 connection and is usually the simplest choice for one legacy peripheral. A two-port card can operate two compatible RS-232 devices at once, making it more convenient for paired scanners, terminals, controllers, or printers. Two ports do not guarantee that every device can communicate simultaneously, so confirm software support for the intended combination.
What does pin 9 power mean?
Pin 9 on a DB9 serial connector is sometimes used to carry power or an additional handshake signal. The StarTech PEX1S953LP supports selectable 12V, 5V, or no power, while the PEX2S953LP allows individual port configuration. Some devices do not need pin 9 power, and applying the wrong setting can damage equipment, so consult both manuals before connecting the peripheral.
How do I find the COM port number?
After installing the hardware and driver, the operating system normally assigns a serial identifier. On Windows, check Device Manager under the Ports or Universal Serial Bus controllers category, depending on the driver. Linux systems may expose the port as a device such as ttyS0 or ttyUSB0. Your application must be configured with the same port identifier and the peripheral's required communication settings.
Can I connect modern USB devices to an RS-232 card?
Only if the USB device specifically includes or requires an RS-232 interface. An ordinary USB-to-serial adapter and a PCIe RS-232 card serve different purposes: the former typically exposes a serial port over USB, while the latter adds physical DB9 connectors to the computer. Most modern printers and scanners use USB directly, so verify the connector on the device before purchasing legacy serial hardware.
Final Thoughts on Choosing the Best Pcie Serial Port Card
The PCIE-SE2 stands out as the best overall general-purpose option because it combines two ASIX AX99100 ports with broad Windows support and useful bracket flexibility. The dual-port AX99100 card is the best value choice for buyers who want the same core two-port architecture, while the StarTech PEX2S953LP is the most compelling premium recommendation thanks to 921.6Kbps per-port throughput, independent pin 9 configuration, and a strong rating.
Prioritize the details that directly affect your equipment: number of DB9 connectors, required baud rate, operating-system version, case clearance, driver method, and pin 9 signaling. A simpler one-port card is preferable to an overfeatured model when only one peripheral is involved, while a WCH382 or combo card may be the better choice for specific 16C550 or parallel-printer installations.
Finally, verify the current product listing, driver availability, included accessories, and technical specifications before buying. Retail listings can change, and product configurations are not always identical between revisions. Comparing the present requirements of your computer and connected devices against the latest manufacturer documentation will help avoid an avoidable compatibility problem.