Dumping a KA53 (VAX 4000 105A) system rom

[marmotking]

Lately I've been trying to dump my VAX system ROMs in case the EPROMs or EEPROMs suffer bit rot. The KA53 (i.e. VAX 4000 105A) doesn't have EPROM chips on the motherboard, so I was attempting to use the boot console's "examine" command to grab the system ROM contents. This has worked before on other CPUs such as the KA660 (VAX 4000 200).

One of the KA53 manuals, available here:

http://manx.classiccmp.org/collections/mds-199909/cd1/vax/473abmgc.pdf

shows that the boot ROM starts at 20040000, which seems to be the standard location. However, it also states that the boot ROM is 512K. I've tried dumping it with:

>>> examine /p /q /n:ffff 20040000

which should dump 512K bytes (0xffff + 1 quadwords which is 512K bytes). However, shortly after the 256K boundary, it gives me a memory fault. Just like other machines like the KA660 (which only has 256K of boot rom) do.

Any idea if this ROM really is 512K and if it is, what the physical address of the rest of the ROM is? I know that in this case the ROM is actually in EEPROM.

Any suggestions would be more than appreciated!

 

[marmotking]

So I opened up the machine and found that there are 4 of the 28F010 feprom's in there. So that is indeed 512K of memory. I also found the following in section 4.6.6 of EK-473AA-MB, "VAX 4000 Model 100 KA52 CPU System Maintenance" the following text (which probabily also applies to the KA53):

"On the KA52, halt-protected space spans the first half of the 512K byte
FEPROM from 20040000 to 2007FFFF. The second half of the FEPROM has
data which is loaded into memory and run."

So, I can easily dump the first half. I cannot seem to find how to get to the second half. I don't find any description anywhere about what memory address the second half occupies while in the FEPROM nor can I figure out where in RAM it's being copied. Does this ring a bell with anyone?

Here's a link to the referenced document:
decdoc.itsx.net/dec94mds/473aamga.pdf