I think I've had enough of memory segmentation! Time to move on...
OK, on to the PROM on the 3c515-tx. The manual states that it can take up to 32K PROMs. I assume that is 32 Kilobytes and not kilobits. What I am puzzled by is that the boot ROM DIP-32. If the max is 32 KByte, why would they not use a DIP-28 socket? It got me wondering if the pinout is non-standard. The manual says the part number for the PROM is 3c515TRIROM, but there is very little reference to this online with the exception of some IC part quote places.
I have two of these 3c515-tx cards. I installed a Winbond W27E257-12 EEPRM, which is DIP-28, into the DIP-32 socket on the 3c515-tx with left-most 2 pairs of pins not being used on the socket. Here is a visual of a 3c515-tx: http://ironalbum.pvk13.org/3c515tx-comp_side.jpeg
I removed the Lo-Tech card, installed the 3c515-tx with the W27E257 installed, and booted the computer. I ran 3c515cfg which sees the network card, but the card's connection LED's don't light up. The config utility also cannot detect the network. Is my 3c515tx broken and did the installation of the W27E257 break it, or did the card come broken in the mail? Using my other 3c515-tx card (without the EEPROM installed), the LAN lights turn on and the cfg util can find my network.
EDIT: OK, the boot PROM in the defective 3c515-tx card works! I can set C8000h from within the DOS cfg utility. I then put a "burned" eeprom into my working 3c515-tx and it also works. It was kind of tricky to get the Base Address options to show up in the DOS cfg utility though. The 3Com DOS CFG utility has these options:
C8000h <<<---- I have selected this one
[I also noticed how the 3com address convention agrees with the motherboard's convention and not the XTIDE convention]
So I guess that other 3c515-tx card came DOA. It is getting more difficult to get money back from eBay these days unless the hardware has been tested within 30 days. But since the config util detects the card and there just seems to be a send/receive issue over the port, any idea which component may be dead?