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Thread: PC-DOS 3.2 for 5150

  1. #11
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    Quote Originally Posted by maxtherabbit View Post
    Yes it's the lo tech. I'm content with the amount of free memory I have now and don't want to sacrifice 2MB of EMS for 64kB of UMB.
    Yeah. I'm just curious if it works on anyone else's hardware. The card I built *should* be 100% "register compatible" with the Lo-Tech card and it works with the EMM driver for it, but technically the hardware's completely different so, I dunno, gremlins.
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  2. #12

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    Oh well I'll be happy to test it

  3. #13
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    Quote Originally Posted by Eudimorphodon View Post
    Anyway, using this lets you use USE!UMB.SYS to do upper memory stuff with MS-DOS 5 or later while saving the ~5k or so the EMS driver takes up. Obviously you don't get to use EMS when using it for this.
    IMO, it's more effect to load the driver and then load QRAM so that QRAM can extend 640K to 736K, assuming the LIM EMS board allows mapping into A000 and beyond (Intel boards don't, I've unfortunately verified). Trading 5K of driver to 91K more space in low DOS RAM, breaking the 640K barrier, is totally worth it.
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  4. #14
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    Quote Originally Posted by Trixter View Post
    IMO, it's more effect to load the driver and then load QRAM so that QRAM can extend 640K to 736K, assuming the LIM EMS board allows mapping into A000 and beyond.
    The LTEMS board doesn't have any mapping capability; the driver is "EMS 4.0" compliant but only because under the EMS 4.0 standard basically *any* EMS 3.2-compliant board can be, all the hardware mapping features from EEMS were completely optional. You get the 64k page frame and nothing else.

    (Therefore using the driver instead of a static shim doesn't buy you anything. All the shim does is cram the values 0-3 into the paging registers to make sure each points to a unique 16k page of RAM instead of potentially pointing at the same page or empty space. The latter is possible because the paging system allows more pages of memory than are actually implemented.

    Certainly things would be different with a "real" EMS 4.0/EEMS board.)
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  5. #15

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    Yep. I built the lo tech on a lark just to play with it but it is pretty limited compared to a rampage or bocaram or above board. However it is *very* fast. Being limited to only a 64kB page frame (that is also 64kB aligned) is kind of lame

  6. #16
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    Quote Originally Posted by maxtherabbit View Post
    Yep. I built the lo tech on a lark just to play with it but it is pretty limited compared to a rampage or bocaram or above board. However it is *very* fast. Being limited to only a 64kB page frame (that is also 64kB aligned) is kind of lame
    I built it into my ridiculous Tandy 1000 expander mostly because I had logic to spare in the GALs and wanted to soak it up with something. Itís primarily good for shock value. (ďEMS in a 1000 EX?! Thatís un-possible!Ē.)
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  7. #17
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    Dammit. I wonder if I can cancel my LTEMS order. I recall bringing this up during development but I must have made assumptions.

    I've been trying to extend DOS past 640K on my 5160 and have been thwarted at every turn. All my EMS boards are Intel, and Intel followed IBM's recommendations to the letter and WILL NOT map into A000. I bought a LT memory board and put 64K directly into A000, but all of the tricks (704K.COM, etc.) seem to lock up the system even though they test the RAM as ok. (Meanwhile, on my goofball AT&T 6300 with an EEMS 3.2 board, EMS + QRAM = 736K free DOS RAM effortlessly.)
    Last edited by Trixter; October 18th, 2020 at 07:48 PM.
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  8. #18
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    Quote Originally Posted by Trixter View Post
    I bought a LT memory board and put 64K directly into A000, but all of the tricks (704K.COM, etc.) seem to lock up the system even though they test the RAM as ok.
    That's really weird; I wonder what in the world they're choking on. There's certainly nothing special about the lo-tech RAM card that should cause problems. If the memory wasn't testing OK I'd almost wonder if there's something up with the 5160's internal memory decoding that's causing some weirdness.

    (One of the things I did with my Tandy 1000 expansion is I actually made it an option to put the EMS page frame at A000; since the T1000 has CGA-like video there's no conflict and it frees up more of the upper memory to be filled with the 128k of spare RAM it has specifically for UMBs. I haven't found anything that chokes on an EMS page frame at that location, at least. Unfortunately I can't test doing the "704k" thing because of the Catch-22 that a Tandy 1000 effectively creates a 16k (or bigger) memory hole between DOS memory under 640k and the A-page unless you plug in a VGA card... at which point the A-page is needed for other things.

    I've sometimes wondered if anyone would be interested in an ISA version of my card, IE, a new "Six Pack" for 256k-or-bigger XTs; doing a 704/736k backfill would be an easy option to add.)

    I've kicked around in my head a few times the idea of making a fully EMS 4.0-compatible card that can do actual remapping, maybe using a fast SRAM as the mapping register, but it's a darn complicated standard and I'd have *no prayer* of writing the necessary driver myself. If someone has sufficiently detailed specs to an existing card maybe making a software compatible one would be an outside possibility.
    Last edited by Eudimorphodon; October 18th, 2020 at 08:28 PM.
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  9. #19

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    If you were going to go the distance with a new 6 pak of sorts, allowing it to backfill conventional from 256kB up AND provide EMS while being able to page flip them over the whole range like a LIM 4.0 card would be bad ass

  10. #20
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    AKA "an EMS 4.0 board" (backfilling and mapping are core functions)
    Offering a bounty for:
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    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

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