jh1523
Experienced Member
I have recently obtained a Biostar MB-1212C motherboard, 286 with SCAT chipset (82c235), comes with a 12MHz CPU and 1M of memory in DIP sockets. It also has 4 SIPP sockets for up to 4MB memory. There is no jumper to select between the DIP and the SIPP. Here is the entry in TH99: https://stason.org/TULARC/pc/mother...OTECH-INTERNATIONAL-CORPORATION-286-MB-2.html
It comes with an AMI BIOS that allows for setting some SCAT chipset specific features, but the only thing related to memory is whether to enable/disable shadow RAM, move 384k above 1MB and use as extended memory (mutually exclusive with the shadow RAM of course) and some memory timings.
With the on-board memory, if I enable shadow RAM it counts the base memory at boot, finds the shadow RAM and no extended memory. If I disable the shadow RAM, it finds 384k of extended memory. This is all as expected.
I am trying to add more RAM however. I haven't been successful so far.
If I add memory to the SIPP slots but don't remove the DIP chips, it acts as if the SIPP didn't exist. Occasionally on boot it will find only 512k base memory, but that's not consistent. If I remove the DIP chips and leave only 4x1MB memory in the SIPP slots, it doesn't boot. Only gives me 3 short beeps at boot, which for AMI means failure of the first 64k memory.
Moreover, with the original DIPs installed I tested several extended memory cards trying to add memory above 1MB. None of the memory on the cards is recognized, even by an extended memory testing program (testext.exe), The cards were correctly jumpered to add between 512kB and 2MB of extended RAM just above the first megabyte. The cards I used were: Compaq Portable II extended memory card (2MB), AST Rampage286 (512kB) and Kouwei KW-518 (2MB). All 3 cards are known working in other machines. Similarly the memory sticks work in other computers. I tried each card in several ISA slots with the same results. The ISA slots on this motherboard are all good, they work well with other cards (VGA, I/O etc). The motherboard is very clean, with absolutely no corrosion and no bad solder joints.
I also tried a BIOS from another SCAT motherboard (GW-286CT); this BIOS is probably somewhat newer, but the options in it are more or less equivalent to the original BIOS. It works with the DIP memory, but like the original BIOS doesn't boot with the SIPP, and memory on ISA cards isn't recognized.
I don't know how to proceed from here.
It comes with an AMI BIOS that allows for setting some SCAT chipset specific features, but the only thing related to memory is whether to enable/disable shadow RAM, move 384k above 1MB and use as extended memory (mutually exclusive with the shadow RAM of course) and some memory timings.
With the on-board memory, if I enable shadow RAM it counts the base memory at boot, finds the shadow RAM and no extended memory. If I disable the shadow RAM, it finds 384k of extended memory. This is all as expected.
I am trying to add more RAM however. I haven't been successful so far.
If I add memory to the SIPP slots but don't remove the DIP chips, it acts as if the SIPP didn't exist. Occasionally on boot it will find only 512k base memory, but that's not consistent. If I remove the DIP chips and leave only 4x1MB memory in the SIPP slots, it doesn't boot. Only gives me 3 short beeps at boot, which for AMI means failure of the first 64k memory.
Moreover, with the original DIPs installed I tested several extended memory cards trying to add memory above 1MB. None of the memory on the cards is recognized, even by an extended memory testing program (testext.exe), The cards were correctly jumpered to add between 512kB and 2MB of extended RAM just above the first megabyte. The cards I used were: Compaq Portable II extended memory card (2MB), AST Rampage286 (512kB) and Kouwei KW-518 (2MB). All 3 cards are known working in other machines. Similarly the memory sticks work in other computers. I tried each card in several ISA slots with the same results. The ISA slots on this motherboard are all good, they work well with other cards (VGA, I/O etc). The motherboard is very clean, with absolutely no corrosion and no bad solder joints.
I also tried a BIOS from another SCAT motherboard (GW-286CT); this BIOS is probably somewhat newer, but the options in it are more or less equivalent to the original BIOS. It works with the DIP memory, but like the original BIOS doesn't boot with the SIPP, and memory on ISA cards isn't recognized.
I don't know how to proceed from here.