Difference between revisions of "Mostek MK8022"
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| − | The '''Mostek MK8022''' is a 256 Kbyte [[QBUS]] memory card in a dual QBUS format. | + | The '''Mostek MK8022''' is a 256 Kbyte [[QBUS]] [[main memory]] card in a [[DEC card form factor|dual]] QBUS card-size format, using 64Kx1 [[Dynamic RAM|DRAMs]]. |
| − | No documentation is currently known for this card, but since this card has two banks (i.e. it has a 9x4 array of xx64 64Kx1 chips; i.e. to provide 16 bits wide plus byte parity, there are two groups of 18 chips), it is sometimes possible to repair problems in one. | + | No documentation is currently known for this card, but since this card has two banks (i.e. it has a 9x4 array of xx64 64Kx1 [[integrated circuit|chips]]; i.e. to provide 16 bits wide plus [[byte]] [[parity]], there are two groups of 18 chips), it is sometimes possible to repair problems in one. |
| − | If one bank is picking or dropping bit(s), and the other is not, that meant that data | + | If one bank is picking or dropping bit(s), and the other is not, that meant that [[data path]]s were all OK, and it is a simple matter of finding the bad [[memory]] chips. |
| − | By pulling memory chips (luckily, they were socketed on the board of this type which was examined, so this was pretty painless), it was possible to work out which bits are stored in which chips. ( | + | By pulling memory chips (luckily, they were [[chip socket|socketed]] on the board of this type which was examined, so this was pretty painless), it was possible to work out which bits are stored in which chips. (Unlike many memory cards, it's not semi-random.) |
Low bank: | Low bank: | ||
| Line 44: | Line 44: | ||
D9-H9 seem to be parity. | D9-H9 seem to be parity. | ||
| + | |||
| + | [[Category: QBUS Memories]] | ||
Latest revision as of 01:46, 14 December 2020
The Mostek MK8022 is a 256 Kbyte QBUS main memory card in a dual QBUS card-size format, using 64Kx1 DRAMs.
No documentation is currently known for this card, but since this card has two banks (i.e. it has a 9x4 array of xx64 64Kx1 chips; i.e. to provide 16 bits wide plus byte parity, there are two groups of 18 chips), it is sometimes possible to repair problems in one.
If one bank is picking or dropping bit(s), and the other is not, that meant that data paths were all OK, and it is a simple matter of finding the bad memory chips.
By pulling memory chips (luckily, they were socketed on the board of this type which was examined, so this was pretty painless), it was possible to work out which bits are stored in which chips. (Unlike many memory cards, it's not semi-random.)
Low bank:
| Bit | Chip |
|---|---|
| 01 | H1 |
| ... | |
| 0200 | H8 |
| 0400 | E1 |
| ... | |
| 0100000 | E8 |
High bank:
| Bit | Chip |
|---|---|
| 01 | F1 |
| ... | |
| 0200 | F8 |
| 0400 | D1 |
| ... | |
| 0100000 | D8 |
D9-H9 seem to be parity.
