jxh@cup.portal.com (Jim - Hickstein) (02/19/90)
I am trying to get an IDEAssociates Supercomm card (PC-002) to work in my NEC APC SX (80386SX, 16MHz), but my driver fails its RAM diagnostics. Hopping into debug, I can see that only the even (low) bytes appear to stick when written, the odd bytes reading back as FF. This sure seems like a problem with SBHE (System Bus High Enable) on the I/O Channel being forced active, even though my 8-bit card (it's only got one edge connector, even) is not requesting 16-bit transfers. A quick look (hah!) at the NEC so-called technical manual for the machine shows a memory configuration register that can cause 0Axxxx, 0Bxxxx, 0Cxxxx, and 0Dxxxx to be either under control of the AMMC, or on the I/O Channel. It is configured correctly. I have tried moving the Supercomm card to different addresses (it can be A, C, D, or E), putting it into the only physical-8-bit slot in the machine (second connector not populated), and slowing down to 8MHz. Nothing changes. Is this a bug in the hardware, such that I cannot use 8-bit memory in these places? Has anyone else run across this? What am I doing wrong? Old-timer that I am, I have managed to isolate it this far, but without a schematic, I'm stuck. I'm getting the scope out shortly, anyway. Please respond by email. Thanks very much. Jim Hickstein jxh@cup.portal.com ...!sun!portal!cup.portal.com!jxh (408) 434-0822