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.
Features.
The 3Com 3c5x9 family of network controllers has various interface combinations of computer bus including ISA, EISA, MCA and PCMCIA. For network connection, 10BASE-2, AUI and 10BASE-T are used.
B = On ISA and PCMCIA adapter numbers indicates that these adapters are part of the second generation of the Parallel Tasking EtherLink III technology.
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 registered 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: 70 ns CMOS static RAM, U1: DIP-28 27C256 style EPROM for boot code, U3: 1024 bit 5V CMOS Serial EEPROM (configuration).
Label:
 Etherlink III
 (C) 1994 3C509B-"C"
 ALL RIGHTS RESERVED
 ASSY 03-0021-"001" REV-"A"
 FCC ID: DF63C509B
Barcode:
 EA=0020AFDCC34C
 SN=6AHDCC34C
 MADE IN U.S.A.
R = Resistor
C = Capacitor
L = Inductance
Q = Transistor
CR = Transistor
FL = Transformer
T = Transformer
U = Integrated circuit
J = Jumper or connector
VR
F
FL70: Pulse transformer
 bel9509 A
 0556-3873-03
 * HIPOTTED
Y1: 20 MHz crystal
 20.000M
 652DA
U50:
 P9512BR
 DP8392CN
 Coaxial Transceiver Interface
T50: Pulse transformer, pinout: 2x8
 VALOR
 ST7033
x00: Pulse transformer
 VALOR
 PT0018
 CHINA M
 9449 C
U4: Plastic package 33x33 pins
 Parallel Tasking TM
 3Com
 40-0130-002
 9513S 22050553
 AT&T 40-01302
Another chip with the same function:
 40-0130-003
 9545S 48324401
 AT&T 40-01303
U6: 8192 x 8-bit 70 ns CMOS static RAM
 HY 6264A
 LJ-70
 9509B KOREA
Another chip with the same function:
 CY6264-70OSC (photo)
U1: Boot ROM
 DIP-28 EPROM
 8,16, or 32 kB (27/28C256) for boot code.
U3: 256 Bit/1K 5.0V CMOS Serial EEPROM
 B 52AH
 93C46
 M8
Q41: N-Channel Logic level Power MOSFET 60V, 11A, 107 mΩ 
 F3055L
 96 45
 (H)H
VR41: 3-Terminal 0.5 A Negative Voltage Regulator (-5V) in D2PAK
 KA79
 M05
ASSY 03-0021-004 REV-B has written on it: U.S. Patents: 
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 For Linux it is "eth".
Patents.
3c509B-C from 1996 specify the use of 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.