Some kind of fast RAM configuration issue?

[commodorejohn]

So here's a problem. I have an Amiga 2500 (Kickstart 3.1) with (currently) two boards in it: an A2630 accelerator with 2MB of 32-bit RAM onboard, and a GVP Impact HC+8 Series II SCSI controller. Until today, the GVP card had 2MB of RAM installed, and all was well with the world. However, I ordered some more SIMMs, planning to max out my Amiga's fast RAM by bringing the GVP card up to 6MB, and that's where things got a little odd. When I installed the SIMMs and set the jumpers for 6MB, the Amiga powered on, went through its basic POST sequence, and...displayed the Kickstart "insert disk" screen.

I set the jumpers back to 2MB and it worked fine, then I tried the 4MB setting and had no trouble; Workbench displayed a total of about 6MB fast RAM. It's only when I set the jumpers to 6MB that it malfunctions and fails to detect the hard disk. However, when I boot into Workbench from a floppy, it does display a total of 8MB fast RAM. What's going on here? Is there some kind of extra "hidden" memory on one of these boards that's throwing the auto-configure for a loop? Or is there memory that the SCSI controller uses to talk to the hard disk, but can't get to because all the fast RAM space is taken?

[commodorejohn]

Hmm, interesting. There doesn't look to be any jumpers for the mask value on the amiga.resource.cx page or the manual therein; is there some other way I'd have to do this? Or with the AddMem route, how do I go about finding out what parameters to use with this card?

[commodorejohn]

Okay, when the GVP card is set for 8MB, ShowConfig shows the A2630 mapped at 0x200000 to 0x3FFFFF and the GVP has two fast RAM slots (0x400000-0x5FFFFF and 0x600000-0x9FFFFF) and one I/O slot (0xE90000-E9FFFF.) However, HDToolbox complains about "driver not installed," yet when I reboot in 2MB mode, it simply doesn't display any drives in the list, despite the hard drive being recognized and bootable. Puzzlement!

[commodorejohn]

Hmm, that's a thought. I'll take a look when I open it up next.

[commodorejohn]

Well, I popped the case today for another card, and the 2630 is configured for 2MB, so I'm kind of stumped. Unless the GVP card somehow attempts to grab 8MB of space when it's configured for anything more than 4MB, I have no idea what the deal would be.

[commodorejohn]

Yeah, I'm figuring that might be easiest. I've got a DKB 2632 now, so it won't matter terribly once I get that working, but once a problem gets on my brain it's difficult to get it to go away :/

[commodorejohn]

Okay, coming back to this again, I did some experimenting while I had my 2000 open and found the following. When the jumpers on the GVP card are set for 6MB, it occupies a block from 0x200000-5FFFFF (4MB) and a block from 0x600000-7FFFFF (2MB.) However, when it's set for 4MB, it occupies one block from 0x600000-9FFFFF. The 2630, when the GVP card is set for 0MB or 4MB, occupies a block from 0x200000-3FFFFF.

I'm kind of wondering if the GVP card is having some kind of conflict with the 2630 over that area at 0x200000 that both of them seem to want. (Wish I knew more about how Zorro II memory partitioning worked!) I have a copy of AddMem, but I'm not sure if that would be useful in this situation - is it possible to use it so that I can have the GVP card configured for 4MB and manually add the remaining 2MB into 0x800000-9FFFFF?