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Thread: RAM on a 286 - EMS, XMS, UMA, HMA, WTF

  1. #1

    Default RAM on a 286 - EMS, XMS, UMA, HMA, WTF

    Hi

    so I've got a beautiful, old 286 up and running again (I love tinkering with old computers) and because I was veeery young when I got my first 286, I can't really remember much about memory management.

    What I have found out/done so far:
    - The motherboard has 1 MB onboard
    - BUT it allows me (via jumper config) to either use 640k conventional memory and "ignore" the remaining 384k OR use 512k conventional memory + 512k of UMA (upper memory).
    - I have bought, assembled and installed one of these 2MB EMS cards: https://texelec.com/product/lo-tech-ems-2-mb-pcb/
    - If I configure the motherboard to 512k/512k, the biiig downside is, that I'll never get more than 500-something conventional memory free, regardless of how well I optimize driver loading
    - If I configure it to 640k/0k, I don't have UMA, don't have himem.sys loaded, don't have UMB and so on.
    - EMS memory (link above) is installed and LTEMM driver is up and running, 2MB EMS detected and ready

    What I ask myself:
    - What would be the ideal config to get as much conventional memory as possible + utilize EMS as good as possible
    - Would EMS even be used by any software except games which specifically ask for EMS?
    - What about QRAM or QEMM or Above Disc?

    btw. himem.sys says "no available extended memory was found" when using the 640k/0k config.

    Thanks

  2. #2

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    Look for a 'remap' option in the setup. This will place (remap) that ignored 384K above the 1 MB. boundary making it available to use as XMS and let himem.sys load.

    Forget QRAM unless you have a C&T chipset.

    Forget QEMM as it requires a 386.
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  3. #3
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    Is the board giving you 512kB of UMA or 512kB of extended? I have seen a few that gave the later which would give you HIMEM.

    What you need is to find a way for the EMS board to backfill the top 128kB which would give 640kB. EMS 4.0 drivers should do that but the functionality does not seem to be listed at the lo-tech web site.

    EMS can also be used for a disk cache which is probably the best default case. Most games and the like only used a small amount of EMS.

    Is this a Phillips system?
    Last edited by krebizfan; August 28th, 2018 at 07:37 PM.

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    I believe the lo-tech board provides EMS 3.2. However, you might be able to use QRAM with EMS if you want to load TSRs high; I'm doing that with QRAM on my 8088 with a hardware EMS 4.0 board.

    Quote Originally Posted by nemail View Post
    - If I configure the motherboard to 512k/512k, the biiig downside is, that I'll never get more than 500-something conventional memory free, regardless of how well I optimize driver loading
    Yes, don't do that. Keep the 640k.

    Would EMS even be used by any software except games which specifically ask for EMS?
    The only game I know of that can use EMS for additional features and still runs on a 286 is the very first Wing Commander. Wing Commander uses EMS for speech during the flight sequences. Other than that, if you have a slow hard disk, you can use EMS as a disk cache.

    EMS is used more in application software, but since you mentioned games, I won't go into which applications.
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  5. #5

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    Will the lo-tech board work with an AT/286? It is only 8-bit.

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    Yes. Memory accesses won't be as fast as with a 16-bit memory board, but it will work.
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  7. #7

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    Hi

    thanks for your answers and sorry for the delay.

    Quote Originally Posted by Stone View Post
    Look for a 'remap' option in the setup. This will place (remap) that ignored 384K above the 1 MB. boundary making it available to use as XMS and let himem.sys load.

    Forget QRAM unless you have a C&T chipset.

    Forget QEMM as it requires a 386.
    The BIOS is very spartanic, it only allows me to set the amount of memory above 1 meg and below 1 meg. however if I jumper it to 640k conventional memory, it always gives me a memory error during bootup, unless, I set 0 KB above 1 meg within the BIOS.
    So essentially I can choose between 512k conventional and 512k XMS or 640k conventional and 0k XMS memory. Very unfortunate...

    Is the board giving you 512kB of UMA or 512kB of extended? I have seen a few that gave the later which would give you HIMEM.
    XMS. But if I do that, I only get 512KB of conventional memory, which is kind of crappy...

    What you need is to find a way for the EMS board to backfill the top 128kB which would give 640kB.
    That'd be cool, maybe using this one? https://www.lo-tech.co.uk/wiki/1MB-RAM-Board
    Not an EMS board but might do the job?

    Is this a Phillips system?
    Nah, it is this board: 286_10_512.jpg

    I believe the lo-tech board provides EMS 3.2. However, you might be able to use QRAM with EMS if you want to load TSRs high; I'm doing that with QRAM on my 8088 with a hardware EMS 4.0 board.
    Will that work without XMS?

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