PROM Dumps

Hardware questions and modifications

PROM Dumps

Postby GHiero » Sun Apr 05, 2015 11:40 am

I was looking through the PCjr. schematics and wanted to find out if there were any custom chips on the system board other than the Video Gate Array at ZM36. I found no others after making a list of the 80 integrated circuits on the system board, but I did find a pair of proms at ZM52 (256x8) and ZM56 (256x4). I am not surprised because the PCjr can make a functional system where an IBM PC uses double the chips to achieve a similar level of peripheral support (game, async, video). The IBM PC XT also uses a PROM, but the IBM PC AT uses PALs, which are much harder to clone. Has anyone ever dumped the PCjr. PROMs?
Attachments
PCjr ICs.ods
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GHiero
 
Posts: 112
Joined: Wed Oct 16, 2013 7:53 pm

Re: PROM Dumps

Postby alanh » Sun Apr 05, 2015 10:10 pm

Yes I have. ZM52 raw dump:
Code: Select all
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
FFFFFFFF6FFFFFFF7BFFFFFF5FFFFFFFFFFFFFFF7DFFFFFF77FFFFFFFFFFBFBF
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF
6FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF77
FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF7E7EFFFFFFBF

ZM52 decoded (rough):
Code: Select all
bit 0 - along with ZA3 for /b845
-----
I/O 0x3d0
I/O 0x3d8

bit 1 - /NMI CS
-----
I/O 0x0a0

bit 2 - /TIMER CS
-----
I/O 0x040

bit 3 - /SERIAL, SOUND CS
-----
I/O 0x0c0
I/O 0x2f8

bit 4 - /GAME, INTR CS
-----
I/O 0x020
I/O 0x200

bit 5 - /8255 CS
-----
I/O 0x060

bit 6 - /MODEM, FLOPPY CS (also feeds /CARD SLCTD)
-----
I/O 0x0f0
I/O 0x0f8
I/O 0x3f8

bit 7 - /I/O ON CARD (also feeds /CARD SLCTD)
-----
I/O 0x020
I/O 0x040
I/O 0x060
I/O 0x0a0
I/O 0x0c0
I/O 0x200
I/O 0x2f8
I/O 0x3d0
I/O 0x3d8


ZM56 raw:
Code: Select all
060606060606060606060606060F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F040F0F0F
0F0F0F0F0F0F0F0F0303030303030303030303030303030303030303030F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F
0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F0F


ZM56 decoded (rough):

Code: Select all
bit 0 - /VIDEO RAM CS (gate enable for video subsystem back to CPU)
-----
MEM 0x00000
MEM 0x08000
MEM 0x10000
MEM 0x18000
MEM 0xb8000

bit 1 - Mux control - CPU PG0-2 to CPU_A14-16
-----
MEM 0xb8000

bit 2 - /ROM_SEL
-----
MEM 0xd0000
MEM 0xd8000
MEM 0xe0000
MEM 0xe8000
MEM 0xf0000
MEM 0xf8000

bit 3 - /MEM ON CARD
-----
MEM 0x00000
MEM 0x08000
MEM 0x10000
MEM 0x18000
MEM 0xb8000
MEM 0xd0000
MEM 0xd8000
MEM 0xe0000
MEM 0xe8000
MEM 0xf0000
MEM 0xf8000


See this thread for more information:

viewtopic.php?f=1&t=377&start=10
alanh
 
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Location: Atlanta, GA


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