CMV-4000

From Computer History Wiki
Jump to: navigation, search

The Camintonn CMV-1000 and CMV-4000 are a pair of QBUS memory cards, in quad QBUS card-size format, with capacities of 1 Mbyte and 4 Mbytes, respectively. They both use the same PCB, and have capacities of 1 Mbyte when using 64Kx1 DRAMs, or 4 Mbytes when using 256Kx1 DRAMs.

Configuration

No original Camintonn documentation is currently available; configuration information will therefore provided here shortly.

Repair

Although no documentation is currently known for this card, since this card has eight banks (i.e. it has a 8x18 array of xx64 or xx256 chips; to provide 16 bits wide plus byte parity, there are eight groups of 18 chips), it is sometimes possible to repair problems in one.

If one bank is picking or dropping bit(s), and the others are not, that meant that data paths were all OK, and it is a simple matter of finding the bad memory chip(s).

By pulling memory chips (luckily, they were socketed on the board of this type which was examined to create this page, so the process was fairly painless), it was possible to work out which bits are stored in which chips. (Unlike many memory cards, it's not semi-random.)

The card has 18 columns, labeled '0'-'7', 'P0', '8'-'15', and 'P1'. These are exactly like what they sound like: the 16 bits of a word, plus a parity bit for each byte. The exact bit to chip correspondence is:

Bit Column
01 0
...
0200 7
0400 8
...
0100000 15

Similarly, there are 8 rows of memory chips, labelled 'A' through 'H', and these are the banks, with 'A' being that at the lowest address on the card. The exact addresses are:

Row Bank starting address
CMV-1000 CMV-4000
A 0 0
B 0400000 02000000
C 1000000 04000000
D 1400000 06000000
E 2000000 10000000
F 2400000 12000000
G 3000000 14000000
H 3400000 16000000