A3000 Custom chips

RAMSEY and DMAC

The RAMSEY and DMAC chips are important A3000 custom chips that, among other things, implement a part of the A3000's onboard DMA SCSI host adapter.

Nearly all A3000 were delivered with the revision combination of DMAC-02 and RAMSEY-04. The problem with this combination is, the DMAC-02 does not like 68040 boards like the A3640. There are both heat and timing problems.

If you are lucky, the tolerances of your DMAC-02 are wide enough to work together with the A3640. If you are not so lucky, SCSI will not work correctly anymore with the A3640 installed.

To overcome this problem for the A3000T-040, Commodore designed new revisions of these chips: RAMSEY-07 and DMAC-04. If your DMAC-02 has problems with the A3640, all you would need to do is to exchange your old RAMSEY and DMAC revisions with the newer ones. But in reality, you can not buy a DMAC-04. They are no longer available anymore.

The RAMSEY-07 is available as a spare part (because it is also used in the A4000T), but this will not help you. The problem is in the DMAC, not in the RAMSEY and a RAMSEY-07 together with a DMAC-02 does not work at all. You need either both chips in the old revisions, or both in the new revisions.

If you have an extremely old A3000, you might even have a DMAC-01. This one runs very hot and has even more problems with '040 board. I also heard of a RAMSEY-03, but don't know any difference to RAMSEY-04.

So, if you have a DMAC that does not work with the A3640, you are basically out of luck. What you could do in this case:

Buy another DMAC-02 (still available) and hope that one works with the A3640 by chance.
Replace the onboard SCSI host adapter by one on a Zorro II or Zorro III plug in card.
Forget about the A3640 and either don't use an '040 board, or use one with a SCSI host adapter of its own.

BUSTER

The BUSTER chip (or more exactly Super-Buster, as the original Buster is a different chip used in the newer A2000s) is important for the Zorro-III slots in your A3000. There are many different revisions of it, but any of them should work with the A3640. Your A3000 (if not upgraded) probably has a BUSTER revsion 05, 06 or 07.

Having said that, you might still want to upgrade your BUSTER to a revision 11 part when you install the A3640. This is no must, but a good idea. The revision 11 BUSTER implements Zorro-III DMA, so you can use cards like the Fastlane Z3, which is not possible with older BUSTERs. The rev. 11 BUSTER is also faster that previous versions and more compatible with different plug in cards.

There is a BUSTER rev. 09 available, too. Do not buy this one, it also tries to implement Zorro-III DMA but has a bug in this. The rev. 11 part also is the only one, which has an extra hack to fix a bug in a different A3000 chip.