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PROM Dumps
Posted: Sun Apr 05, 2015 11:40 am
by 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?
Re: PROM Dumps
Posted: Sun Apr 05, 2015 10:10 pm
by 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