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Problem with memory on 286 (SCAT)

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    #16
    Originally posted by jh1523 View Post
    So it seems that it's very important for this motherboard that parity is enabled everywhere. Still doesn't work with SIPP but at least I have a way of adding memory.
    Maybe the SIMM to SIPP converters you are using don't support the parity chips on your SIMMs and they're being read as non-parity memory.

    Originally posted by jh1523 View Post
    With UMBs provided by the chipset and extended/expanded memory from the ISA boards I can start progressing towards getting a useful system. The SCAT chipset also has a driver that allows conversion of XMS to EMS so you can get the best of both worlds on a 286.
    FWIW, QRAM should work with that chipset.

    QRAM is basically like QEMM but for a 286 and it's only for the C&T chipset. It's quite a powerful memory manager for a lowly 80286!
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

    Comment


      #17
      Originally posted by Stone View Post
      Maybe the SIMM to SIPP converters you are using don't support the parity chips on your SIMMs and they're being read as non-parity memory.
      Doubtful. Essentially it's a pin-for-pin conversion from 30-pin SIMM to 30-pin SIPP. Which have the same pinout.
      FWIW, QRAM should work with that chipset.

      QRAM is basically like QEMM but for a 286 and it's only for the C&T chipset. It's quite a powerful memory manager for a lowly 80286!
      I know. I have used qram together with scatemm.sys and himem.sys to get UMBs, EMS and XMS together on a SCAT chipset system before. Pretty much the pinnacle of the 286 world.

      Even works in emulators e.g. in PCem when emulating a 286 with a SCAT BIOS.

      Code:
      DOS=HIGH,UMB
      DEVICE=C:\DOS\HIMEM.SYS
      DEVICE=C:\QRAM\QRAM.SYS
      DEVICEHIGH=C:\SCATEMM.SYS
      With a 2MB extended memory card and the BIOS configured to allocate 1MB to EMS this gets me: 192kB UMBs, 1MB XMS and 1MB EMS.
      Last edited by jh1523; October 10, 2018, 04:56 AM.
      I/O, I/O,
      It's off to disk I go,
      With a bit and a byte
      And a read and a write,
      I/O, I/O

      Comment


        #18
        I was trying to enhance this computer by sticking the XTIDE BIOS extension into the main BIOS area, which I've done successfully in the past if the main BIOS chip has enough empty space. The GW286 BIOS that I've been using for testing doesn't have empty spaces, but the motherboard's original BIOS (which I'll be attaching to this post for reference) at first look has some holes in it, including a yummy one right at 0xF4000 and big enough to fit a 12kB extension. So I downloaded the latest XTIDE AT large (r598 ), calculated the checksum and adjusted it, then pasted it in there... and the computer doesn't boot, halts with a BIOS checksum error.
        But I adjusted the checksum! Even the whole BIOS checksum is the same! WTF.
        I tried different things for a while until it occurred to me.

        What if that empty space isn't in fact empty? The very beginning of the ROM code is another extension, in fact the motherboard's setup program. It ends way before F4000. There is another smaller piece of code right before F8000, which I hadn't looked closely before. It turns out that the second piece of code is still part of the setup program. And the header of the setup program claims 0x40 512-byte blocks of code, i.e. 32kB or half the ROM. Dammit.
        Whoever compiled this ROM got greedy and took over a bunch of empty space which I can't use for anything now. I'll have to put XTIDE somewhere in the C, D or E segment.

        (edit) Unless.... unless I decide to delete all of the setup program from the ROM and put XTIDE and other stuff there instead. And will have no setup in ROM anymore. Maybe I can convert the setup from a BIOS extension to a .com or .exe program. Gonna have to start looking that up. Then I could run it from floppy when needed.
        (edit2) no that won't work... I did a little bit of code disassembly, the code used absolute jumps which make it tied to the range of addresses where it's originally located. Won't run unless at 0xE0000.
        Attached Files
        Last edited by jh1523; October 9, 2018, 07:51 AM.
        I/O, I/O,
        It's off to disk I go,
        With a bit and a byte
        And a read and a write,
        I/O, I/O

        Comment

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