Samiksha Jaiswal (Editor)

3Com 3c509

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3Com 3c509

3Com 3c509 is a line of Ethernet IEEE 802.3 network cards for the ISA, EISA, MCA and PCMCIA computer buses. It was designed by 3Com, and put on the market in 1994.



The 3Com 3c5x9 family of network controllers have different interface combinations of computer bus like ISA, EISA, MCA and PCMCIA. And for network connection uses 10BASE-2, AUI and 10BASE-T.

The DIP-28 (U1) EPROM for network booting may be 8, 16 or 32 kByte size. This means EPROMs of type 64, 128, 256 kbit (2^10) are compatible, like the 27C256.

Boot ROM address is located between 0xC0000 - 0xDE000.

Teardown example, the 3c509B-Combo

The Etherlink III 3C509B-Combo is registred with the FCC ID DF63C509B. The main components on the card is Y1: crystal oscillator 20 MHz, U50: coaxial transceiver interface DP8392, U4: main controller 3Com 9513S (or 9545S etc.), U6: 8 kByte 70 ns CMOS static RAM, U1: DIP-28 27C256 style EPROM for boot code, U3: 1024 bit 5V CMOS Serial EEPROM (configuration).

Connector for the computer bus: ISA 16-bit

Connections for networking: 10BASE-T (8P8C), AUI (DA-15), 10BASE2 (BNC)

Driver setup

Some of the possible ISA I/O bases are 0x280, 0x300, 0x310, 0x320, 0x330, 0x340, 0x350. And IRQ 5, 7, 9, 10, 11, 12. The driver for OpenBSD, NetBSD and FreeBSD is "ep", For Linux it is "eth".


3c509B-C from 1996 specify the use of U.S. Patent 5,307,459 with a priority date of 1992-07-28.

The patent describes a method where a data transfer counter triggers a threshold logic that generates an early indication or interrupt signal before the transfer is completed. The adapter also writes timing information into status registers such that a device driver can optimize for any latency.


  • PC/TCP Packet Driver for use with MS-DOS or PC DOS on X86
  • Amiga networking (Miami Network Interface MNI, gg2-3c509.mni)
  • References

    3Com 3c509 Wikipedia

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