I get somewhat slow SCSI speed in my A2500 with a 2630/2632 and GVP 4008 combination but after hooking up a narrow SCSI chain to the CSPPC SCSI in my A4000, I realized that there was a termination issue in the SCSI chain in my A2500. I have a terminated CDRW on one end and a terminated external Jaz drive at the other with the unterminated internal HD in the middle. The SCSI controller is also terminated which is a problem and I only get around 1.3 MB/S max which is about half of what the card should give me. I haven't done it but the fix looks to me like either removing the terminating resitors in the GVP 4008 or reconfiguring the chain with the external connector on the GVP card not used and the termination on the CDRW removed and a SCSI external connector attached the next connector of the internal ribbon cable which will attach to the external Jaz drive. That should give me a proper SCSI chain with both ends terminated.
Oh, and I didn't pay a fantastic amount for my 2632. They are rare but maybe not in such high demand.
