StarTech 1-Port PCI Express RS232 Serial Adapter Card, TAA (PEX1S553LP) | PCIe to DB9, 16550 UART, Window/Linux, [New Version: PEX1S953LP]

StarTech.com

StarTech.com StarTech 1-Port PCI Express RS232 Serial Adapter Card

Name: StarTech 1-Port PCI Express RS232 Serial Adapter Card, TAA (PEX1S553LP) | PCIe to DB9, 16550 UART, Window/Linux, [New Version: PEX1S953LP]
Brand: StarTech.com
SKU: B0041ULUX6

Bottom line: The StarTech.com StarTech 1-Port PCI Express RS232 Serial Adapter Card: Native ASIX MCS9922CV-AA single-chip design cuts CPU load up to 48% vs bridge-chip cards; main trade-off: superseded by the PEX1S953LP, so StarTech directs new buyers to the newer revision.

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By Mike Perry, Founder & Editor-in-Chief · Listing data updated 2026-10-06

Mike Perry — Hardware researcher since 2014. For retro PC hardware and period-correct parts, synthesises manufacturer documentation, community compatibility lists and marketplace listings rather than first-hand lab testing. Core beat: GPU performance across gaming, rendering, and local-LLM inference. About the author →

Pros & Cons

Pros

✓ Native ASIX MCS9922CV-AA single-chip design cuts CPU load up to 48% vs bridge-chip cards
✓ 256-byte FIFO buffer on the 16550 UART sustains RS232 up to 460.8Kbps
✓ Pin 9 configurable for 12V, 5V, or no power for powered serial peripherals
✓ Ships with low-profile bracket installed plus a full-profile bracket for 1U or tower builds

Cons

✗ Superseded by the PEX1S953LP, so StarTech directs new buyers to the newer revision
✗ Single DB9 port only, no option for a second port on the same card
✗ Linux support documented for kernel 2.6.11 through 4.11.x, older than current kernels
✗ Requires a free PCIe slot, ruling out laptops, mini PCs, and most SFF prebuilts

Manufacturer description

The PEX1S553LP PCI Express Serial Card turns a PCI Express slot into an RS232 (DB9) serial connection. The card is constructed using a native single chip design that lets you harness the full capability offered by PCI Express (PCIe), while reducing the load applied to the CPU by as much as 48% over conventional bridge chip serial cards. The PCI Express RS232 Serial Adapter Card is compatible with a broad range of operating systems, including Windows and Linux Kernel 2.6.11 to 4.11.x, and ships with a low profile/half-height bracket installed, but includes an optional full profile bracket…

SpecPicks Verdict

SpecPicks scored StarTech.com StarTech 1-Port PCI Express RS232 Serial Adapter Card using a rating × review-volume × price-fit model applied to published specs and reviews across the expansion cards category. StarTech.com's expansion cards lineup sits within the broader category mid-tier; price and specs are the deciding factors over brand loyalty here. Judge it on the specification table and the price rather than on sentiment: check the figures that decide your use case, then put it side-by-side with two or three close alternatives in the Compare tool before clicking through.

Common buyer scenarios for expansion cards of this kind: matching it to an existing build, replacing a failing part, or upgrading from a previous-generation equivalent. Check the spec table below against your current setup — particularly socket / form-factor / power-rating fields — and confirm compatibility on the retailer's listing before purchase. Prices and stock are set by the retailer and may have moved since this page was last updated.

Key Features

NEW VERSION AVAILABLE: PEX1S953LP
1 PORT SERIAL CARD: Serial controller card w/ 16550 UART based on ASIX MCS9922CV-AA, allows 1x DB9 port w/bi-directional RS232 speeds up to 460.8Kbps per port, available 256 byte FIFO buffer
OPTIONAL CONFIGURABLE POWER: PCI Express RS232 serial adapter card provides choice of 12v, 5v, or none through pin 9
STANDARD PROFILE & LOW PROFILE BRACKET: PCIe serial card comes w/ a low profile bracket pre-installed & 1x full profile bracket is incl for versatile install; Supports Windows & Linux
VERSATILE APPLICATIONS: For low/standard profile desktop/servers w/ uses in point of sale terminals, PLCs, control/automation in factories, scientific sensors, medical equipment, scanner, oscilloscope

Full Specifications

Brand	StarTech.com
Style	1 Port
Style Name	1 Port
Model Number	PEX1S553LP
Compatibility	Linux
Mfr Part Number	PEX1S553LP
Compatible Devices	Personal Computer
Hardware Interface	PCI
Warranty Description	2-Year
NEW VERSION AVAILABLE	PEX1S953LP
Item Dimensions L x W x H	4.1"L x 3.1"W x 0.8"H
OPTIONAL CONFIGURABLE POWER	PCI Express RS232 serial adapter card provides choice of 12v, 5v, or none through pin 9
Global Trade Identification Number	00065030841733, 00065030841955
STANDARD PROFILE & LOW PROFILE BRACKET	PCIe serial card comes w/ a low profile bracket pre-installed & 1x full profile bracket is incl for versatile install; Supports Windows & Linux
Full listing title	StarTech 1-Port PCI Express RS232 Serial Adapter Card, TAA (PEX1S553LP) \| PCIe to DB9, 16550 UART, Window/Linux, [New Version: PEX1S953LP]

Ready to buy?

StarTech 1-Port PCI Express RS232 Serial Adapter Card, TAA (PEX1S553LP) | PCIe to DB9, 16550 UART, Window/Linux, [New Version: PEX1S953LP] is vintage hardware; the used and vintage market on eBay carries most of the live inventory. Prices and condition vary by seller and move in real time, so we link the live listing rather than quote a cached price. It also has an Amazon listing — check it for current price and availability. SpecPicks earns a small commission on qualifying purchases — thank you for supporting independent review work.

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