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View Full Version : What can be put in an ISA option ROM socket?



TheLazy1
March 18th, 2011, 03:26 PM
Is there a size/type limit?
The googles do nothing. :(

eeguru
March 18th, 2011, 03:36 PM
It will be specific to the device that is doing the address decoding for the ROM chip enable and the socket profile it expects. I found this link (http://www.redhat.com/mirrors/LDP/HOWTO/Network-boot-HOWTO/a628.html) earlier today that I found helpful.

Chuck(G)
March 18th, 2011, 04:06 PM
It depends on the card. Some can be quite useful--some share the ROM address space with memory-mapped I/O or scratch RAM (some SCSI controllers do this).

Exactly what did you have in mind?

TheLazy1
March 18th, 2011, 04:08 PM
I was given an 8bit network card which has a DIP socket, was just wondering what could be put in it.
All I have though are 4Mbit flash chips which probably won't work, but I was curious anyway.

Chuck(G)
March 18th, 2011, 04:26 PM
Most of the ISA NIC cards used 2764 or 27128 PROMs. I suppose you could use the space to furnish support for a device (say, a HD floppy controller pirated from a 16 bit hard drive controller card) in an 8 bit slot that doesn't normally require support. You might think up extra uses...

TheLazy1
March 19th, 2011, 02:30 PM
I only have 256KB flash chips, am I correct in assuming I cannot write a ROM to one and drop it in?

Chuck(G)
March 19th, 2011, 02:34 PM
You can--the easiest way is to write a 64K image 4 times, so the state of the extra address lines doesn't matter.

TheLazy1
March 19th, 2011, 03:14 PM
Cool, so it's the same with roms of other sizes?
I remember reading though that doing the above could cause the rom to activate more than once, oddly enough I cannot find the page that says this anymore.

Chuck(G)
March 19th, 2011, 03:21 PM
Any JEDEC-based ROM that uses the same pins (relative to the far end of the package) for Vcc and Gnd and has the same relative CS/OE pin should work. 256K in place of 64K or 128K is most common, however. You could also use an adapter socket.