PROM Dumps

[GHiero]

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?

[alanh]

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:

http://www.brutman.com/forums/viewtopic ... 7&start=10