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Thread: Problem with memory on 286 (SCAT)

  1. #11

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    Another thing to try (when you get home) is to load himem.sys and also add DOS=HIGH to your config.sys. Maybe there's an issue with the board's A20 Gate handling capability.
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  2. #12
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    Yup, should have done that. I forgot that 286s can use HMA though they can't use emm386.
    I don't have a strong suspicion of A20 problems, since the 384k XMS tested fine - but I haven't run anything from it. Apart from doing that I may try to reseat the KBC, or maybe exchange it temporarily for another one.
    Last edited by jh1523; October 8th, 2018 at 06:24 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

  3. #13
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    Tests I've run so far:

    1. Configured the system with 1M DIP memory for 640k conventional + 384k XMS. Boothed with himem.sys and "DOS=high". DOS is loaded in the HMA and functions correctly. That IMHO eliminates any A20 concerns. If A20 wasn't enabled correctly, no XMS would be available no matter what its source.

    2. Removed the memory chips from bank 1. Confirmed that 512k are recognized at boot and adjusted CMOS parameters. Added a memory card (KW-518 ) configured with 18x64k chips in bank 1 (128k total) and the other banks empty, and switches set to fill 128k starting at 512k. On boot, 640k are counted and are available for DOS. So this card can fill conventional memory. In tests from yesterday, the same card couldn't add any extended memory if it was configured to fill from 1024k.

    Still testing.
    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

  4. #14
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    Hey, some progress!

    3. Went back to testing the Compaq Portable II extended memory card. This one has 2MB on-board, and jumpers to locate the extended memory at: 1M-3M, 2.5M-4.5M, 4.5M-6.5M or 6.5M-8.5M. I started testing it again, set as before to 1M-3M. Before that I noticed in BIOS that parity was disabled. I enabled it, and what do you know, 2M of XMS are recognized by the BIOS. Himem can activate it, and DOS can be loaded in the HMA provided by the card. It's also tested good with the extended memory tester.

    4. Tried to do the same with the AST Rampage 286, but the memory on that one still isn't recognized.

    Still testing.

    (edit) Even with parity enabled, the board won't boot with memory only in the SIPP sockets. Yes, I used parity (9-chip) memory modules.
    Last edited by jh1523; October 8th, 2018 at 05:26 PM.
    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

  5. #15
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    5. Tested AST Rampage 286 again, this time with parity enabled both on the motherboard and the card. It works. The manual however seems to have been written by someone half brain-dead for users that are 3/4 brain-dead. Took me a while to translate correctly the indications in it into useful switch configuration. But hey, it works. Incorrect switch configuration was the cause of failure at #4. (long version: with parity disabled, regardless of switches the extended memory tester couldn't find the RAM on the AST card anywhere between 1M and 16M; with parity enabled it did find the memory but it was further up than expected and being non-contiguous the motherboard wasn't detecting it; correcting the switches brought it back to the 1M boundary and it was found by the motherboard as well)

    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. 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.
    Last edited by jh1523; October 8th, 2018 at 07:09 PM.
    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

  6. #16

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    Quote 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.

    Quote 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!
    ☀☀☀ Visit Take Another Step for both computer and non-computer related discussions. ☀☀☀

    If you're looking for DS/DD or DS/HD 3" or 5" floppy disks, PM me. I've got some new, used, and factory over-labeled disks for sale.

    There is a crack in everything. That's how the light gets in. -- Leonard Cohen

  7. #17
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    Quote 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 10th, 2018 at 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

  8. #18
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    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 Attached Files
    Last edited by jh1523; October 9th, 2018 at 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

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