Compex RL100ATX: History, Specifications, and How to Get It Working Today

Legacy PCI 10/100 Ethernet adapter based on Realtek RTL8139 — overview, driver tips for Windows 98/ME, Linux notes and troubleshooting.

Quick summary

The Compex RL100ATX is a classic PCI Fast Ethernet adapter (10/100 Mbps) that was widely sold in the late 1990s and early 2000s. It is typically built around the Realtek RTL8139 family chipset. Because of the ubiquity of that chipset, the RL100ATX enjoys broad operating-system support and often works “out of the box” on many older systems.

Technical specifications

  • Model: Compex RL100ATX (sometimes listed as RL100ATX 10/100 Base PCI)
  • Interface: 32-bit PCI (PCI 2.x era)
  • Speed: 10/100 Mbps (10Base-T / 100Base-TX)
  • Typical chipset: Realtek RTL8139 family (RTL8139A/B/C)
  • Auto-negotiation: Yes (10/100, full/half duplex)
  • OS support (historical): Windows 98 / ME / 2000 / XP, many Linux kernels

Short history and context

When Fast Ethernet (100 Mbps) became mainstream, chipset vendors such as Realtek produced very low-cost, compact controllers (RTL8139). Small networking companies like Compex soldered those chips onto PCI cards and sold large volumes to OEMs and end users. The RL100ATX is one of those low-cost, high-compatibility adapters that helped desktops move from 10 Mbps to 100 Mbps networking affordably.

Driver and OS compatibility

The important compatibility fact is that the RL100ATX most often identifies itself to the operating system as a Realtek RTL8139 device. That means:
  • Windows ME / 2000 / XP: In most cases the OS contains an appropriate RTL8139 driver and will configure the card automatically.
  • Windows 98 / 98 SE: Windows 98 can sometimes install a built-in driver but may need the Realtek driver INF. Using the “Have Disk…” option and selecting the generic RTL8139 driver usually works.
  • Linux: The kernel module rtl8139 (or 8139too in older kernels) provides broad support; adapters are normally plug-and-play on modern distributions.

Practical installation tips (old machines)

  1. Try the built-in driver first: In Windows 98, when asked for drivers choose “Show all devices” → look for Realtek RTL8139/8139 family drivers.
  2. If you cannot copy files to the machine: use alternative file transfer methods: floppy disk, grab the hard drive and copy files on another PC, write a CD-R, or use a serial/parallel LapLink cable (InterLink) if available.
  3. Windows ME option: Upgrading to Windows ME on the same hardware often brings newer bundled drivers and increases chances of plug-and-play detection for RTL8139 cards.
  4. Linux: Most live CDs or modern installs already include rtl8139 support — the card should work with no extra driver required.
  5. BIOS/IRQ issues: On very old machines, disable unused onboard devices or free IRQs in BIOS if the card is not detected or IRQ conflicts appear.

Troubleshooting checklist

  • No link light: check the cable and switch port; try a different known-good Ethernet cable.
  • Link but no network: confirm IP configuration (DHCP vs static); try pinging the gateway; swap ports on the switch/router.
  • Intermittent drops: test on another switch or directly to another PC (crossover or auto-MDI/MDIX). In Windows, disable checksum/large-packet offload in driver properties if available.
  • Not detected at all: reseat the card, try another PCI slot, check for bent pins, or test card in another machine to verify hardware failure.

Legacy use and modern relevance

The RL100ATX is a legacy device today. For restoration projects, retrocomputing, or small isolated networks it remains useful. However, for modern home/office networks a Gigabit PCIe adapter is recommended because many switches and routers now provide gigabit speeds.

Suggested keywords & tags

Compex RL100ATX, RTL8139, PCI Ethernet, Windows 98 driver, Windows ME, legacy network card

Conclusion

The Compex RL100ATX is a straightforward, widely compatible Fast Ethernet PCI card — a practical choice for older systems. Because it usually uses the Realtek RTL8139 chipset, obtaining drivers or getting it working under Windows ME or modern Linux is rarely a problem. For high throughput modern networks, consider upgrading to a gigabit PCIe card.
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