Bigram 2630 & GVP HC Series II

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Don't Panic. Please wash hands.
  • I know this isn't an issue with the Bigram but just wondering if anyone has any advice. When I install the Bigram none of the Hard drives I have hooked up to my GVP HC-II SCSI controller show up.

    The board itself still shows up in the autoconfig information in SysInfo, but none of the devices attached to it are accessible.



    I think I may have had the same problem without the bigram but trying to use a Microbotics 8Up! Memory board. Is there something I'm missing that might make the GVP HC-II get along with other ram? It doesn't mind the 2MB on the 2630 itself so I thought it wouldn't mind the bigram attached to the 2630 but it appears I am incorrect.

    Here is what GVP Info has to say about the 2 boards:

    The memory config for all 3 pools:

    Thanks for any help anyone can offer.

  • The GVP controller is a DMA controller, but there is no data path for DMA to reach the "big" fastmem, as that's outside the 24-bit address area that is reachable by DMA.

    There should be a switch in the GVP software to disable DMA and go back to PIO mode. That should do the trick.

  • Yes, the 2091 is also a DMA controller. However, it appears to have a detection for non-DMA targets and branches into an alternative routine when DMA won't work - and that's dead slow. The Guru ROM (which was available for both these controllers) will give it back most (if not all) of the performance you know.

    Just to emphasize it again: This is not a problem of BigRam2630, but a general problem of DMA cards in the A2000 that can't reach the accelerator's fast mem.

  • Thanks so much for your help Jens. I looked into information about the guru rom and from what I was able to discern was it required an adapter because it didn't fit into the space of the original roms. I've been unable to source any of these adapters. Do you have a resource you could point me towards to so I can try to accomplish this?

  • Unfortunately no, I don't have a source for such an adapter. I did contact the author for licensing the Guru ROM in the ACA2000, because I totally see this coming many more times if I sell lots of ACA2000 boards. In summer 2020, he mentioned that "another run is in the making", but to behonest, I never saw these adapters for sale anywhere. I'll pick up that conversation again :-)