I have very limited experience with these but if pre-programmed a 28c64 will replace a 27c64. You fit the ROM in socket like others with base at end leaving 1/2 and 31/32 open (for a 32 DIP socket).
Pin 30 in a 32 pin socket should also be VCC which will match up to pin 28 on DIP 28, what you do not get is the Write-Enable line since it is tied to A14 using DIP 28 so you must pre-program the EEPROM. That is all I know...

I usually use scavenged Flash bios roms from motherboards. Then hotflash them in one of a working motherboard with XTIDE or Blop boot, or even mini DOS. Just repeat the needed flash as much as needed. 8KB minimum XTIDE you just have to COPY 8kb + 8kb ..... as long as you get a 512kB binary to hotflash. Use UNIFLASH 1.4. Then you short those pins underneath. Put it is a LAN NIC boot rom socket. And configure the size. Thats about it.

thanks, just knowing the pin alignment is a great help. Makes sense now why those are marked NC. I was wondering which had to line up right gnd or vcc.

my idea was to try and use a pic processor to program the flash eeprom with a host pc over serial. I already have the pic tools so thought it might be fun project while being cheap.

Hi! It's late (or very early) and I'm a bit sleepy, but from what I remember..

EEPROMs and Flash ROMs should be backwards compatible in read-mode.

You can use a binary copy of the same and double it (mirror it).
COPY /B ROM.BIN + ROM.BIN BIGROM.BIN

This works fine, but may take up twice the space in 640-1024KB area.
Edit: Unless the NIC uses a limited address range, of course.
Haven't tried this yet, though. 😅

With some EPROMs/EEPROMs/OTPROM etc, you can take the BIGROM file, write it normaly into the chip an then do the following:

Tie the last address pin to ground or vcc.
This will cut the address range of the chip in half. You can also use this to select the upper/lower half, I believe.
This way, only one part of the BIGROM data can be read out by the network card.
The chip now behave like a chip half its size.

Anyway, please please double check what I said.
In my case, I used a 27C128 OTP that acted like a 2764, if memory serves.
Again, I'm sleepy and can't check right now.
From what I remember, I only had to add a little solder blob between two nearby legs.

Some more information:
https://ist.uwaterloo.ca/~schepers/sockets.html

so i ended up getting the TL866II plus programmer. Ive programed my 28C64B with the ide_386.bin. This should match my chip well at a size of 8 kb.
Ive padded the end with 0's. Ive tried the chip in 2 different 8/16 cards and in a 386 and 486 machine. I cant get it to boot at all.
The only option i really see is in the softset2.exe program to specify the boot rom address. There are quite a few options, but ive been going for D000.
All of the address ranges are 0x1FF in size. There is also an option for the rom program, but these appear to be old type programs so i dont think i need them.
I didnt think this would be that hard, but it still would be great to find someone who is using this card i this way.

Edit: I cant figure out why this wont work. Clearly the card is supporting 8k roms with the range of 0x200(0). I could actually see the xt bios data through umbinfo when the shadow ram was on. But seems like something on the card just doesnt work, see the xt bios data through umbinfo when the shadow ram was on. But seems like something on the card just doesnt work, even though networking with the packet driver has.even though networking with the packet driver has.
I checked the voltage on vpp, vcc lines and its 5 V. I even used a winbond flash chip and no change. I tried a second atmel chip no change. Tried 0x00's and 0xFF's for the alignment space.
Im going to get a 3com etherlink 3, since those seem to be popular.

Edit #2
Finally! I figured it out and it came down to the version of xt ide bios. The whole time i was trying to use the latest build v604. Went back to the v2 beta release and worked perfect. Now onto installing an OS and finally booting this thing.