IIRC, there is a board by DKB that piggy-backs onto the 2630 and allows 112Megs of 32-bit fast ram.  Beats the crap out if the 8 Meg/16-bit limit.

Nope there is no way around the 8 MB limit. Either you switch off the A2630 Ram (not recommendet) or you limit the Ram on the GVP to 4 MB.

The two existing A2630 Ram expansions DKB 2632 and Access32 are a way to have more Ram with a humble A2630 but usually prices for those boards are so high (as they are collectables) that it is cheaper to get an other accelerator alltogether like a Blizzard 2040 that allows for more Ram on the board itself.

Lemmink is right, the only way is to add 32-bit memory via the 2630's RAM expansion connector.  There's no way, other than possibly a major overhaul of several chips on the A2630, to remap the 2630 memory above the ZII address space.  The good news is that the 2630 memory is 32-bit but as Dave Haynie explained, back in the day 8MB was considered a lot of memory and for compatibility with the original 68000 (fallback mode), placing the 4MB in the ZII space allowed use of the memory with the original cpu for compatibility.  He made provision for extra 32-bit RAM via the access connector on the back of the card.  But there is no simple way to change this arrangement.

On the other hand, Dave H has said would be possible to remap the 4MB of 32-bit memory space on the A2620 board, as the signal for doing so is apparently unused on the PAL chip involved.  It would require a PAL replacement and a relatively simple modification using the aforementioned unused signal.  Under this scenario you'd then have 8MB ZII memory available and 4MB of 32-bit memory on the A2620 above the ZII address space; so a total of 12MB.  On the A2630, the unused address signal line was used for something else; probably has to do with the logic to make the A2630 asynchronous with the A2000 m/b.

I think I bought my DKB 2632 (in my hand right now) on eBay for a song just a few months ago.  Maybe it slipped under everyone else's radar.  It did come completely unpopulated, thats why I have not installed it yet.  I haven't tried to find ram for it yet.

@Tjlazer

I would agree using the A2632 rules out using the A2091 controller for the most part (unless you use some third party software hacks), but using a GVP HD+8 controller seems to work fine for me anyway.  The GVP uses it's own special 24-bit dma software scheme so it differs from the A2091 performance wise.

You could always also use a non-dma scsi card like the Trumpcard, ICD or Dataflyer.  The Trumpcard is the fastest afaik non-dma scsi controller out there.

One thing to keep in mind--when doing this, adding RAM especially via the A2632, you will have horrible SCSI performance and problems.

Have you tried masking the buffer so that only 16 bit RAM is used for buffering?

While the DKB 2632 board might be hard to come by, mine takes regular 72-pin ram like that used on my CSPPC board and can be fully populated; this does lead to a lack of address space and for certain ZII boards I've had to lower the amount installed. The A2630 board is a stubborn bugger which does not allow any changes.