Image Map Image Map
Page 3 of 13 FirstFirst 1234567 ... LastLast
Results 21 to 30 of 124

Thread: PC-DOS 3.2 for 5150

  1. #21

    Default

    Quote Originally Posted by maxtherabbit View Post
    like a LIM 4.0 card
    didn't I say that

  2. #22
    Join Date
    Aug 2006
    Location
    Chicagoland, Illinois, USA
    Posts
    6,884
    Blog Entries
    1

    Default

    Sorry, I thought you were implying the creation of a board that used one mechanism to backfill and another mechanism to provide UMBs and EMS.
    Offering a bounty for:
    - A working Sanyo MBC-775 or Logabax 1600
    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

  3. #23
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,083

    Default

    Quote Originally Posted by Trixter View Post
    AKA "an EMS 4.0 board" (backfilling and mapping are core functions)
    If someone wants to write the driver for it I have some ideas for the hardware. The only standards doc I could find for EMS 4.0 is eye-bleedingly opaque, and huge. (And packed with weasel words about what counts as "optional", which is why technically the LTEMS board "counts" as an EMS 4.0 card; if the driver has a stub for 4.0-specific routines that can either fake it in software or returns "Sorry, Dave, I can't do that." then it's an EMS 4.0 board even if the hardware is just 3.2, or even one of those useless software emulators that ran on 286s without mapping hardware.)

    Using a 2k*16b dual-port SRAM like a Renesas 7133 as a mapping register would theoretically handle 65,536 physical pages (which at 16k each would mean 1GB of memory, which I'm pretty sure is more than the standard supports by a whopping margin; that leaves some bits to shave off the top to use to indicate "unmapped", "read only", or whatever.); dividing 1024k into 16k chunks means you need 64 registers to cover the entirety of conventional memory, which means the 2K capacity of the chip would support 32 completely independent alternate register sets, and the chip is available in speeds as fast as 20ns, hopefully fast enough to be able to do chip select based on a "is this page mapped or belongs to something else?" bits shaved out of the 16 output bits.

    (Using a dual-ported SRAM would vastly simplify reading and writing the paging registers; the LTEMS's registers are write-only.)

    Of course, I suppose I would actually want to lay my hands on a machine that could actually use a LIM 4.0 card that has mapping registers. My only ISA (like) computers at the moment are the Tandys and a PC Convertible which still needs a bunch of repairs and is its own stack of weirdness...
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  4. #24
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,083

    Default

    Quote Originally Posted by Trixter View Post
    Sorry, I thought you were implying the creation of a board that used one mechanism to backfill and another mechanism to provide UMBs and EMS.
    Separate mechanisms to do backfill and UMBs and another for an EMS pageframe is a lot easier than an EMS 4.0 board for the cited "what about a driver?" reason.

    (Well, that and the hardware is still a lot simpler and probably cheaper. Maybe there's a 5v CPLD that has enough internal register space that could do the 4.0 mapper job cheaper than the dual-port RAM and supporting hardware I suggested previously, but it's still going to be substantially more complicated. I was able to fit backfill and a slew of switch-selected UMB and ROM decoding options into a GAL 20v8 and still had room to implement the supporting logic for an LTEMS-compatible EMS 3.2 frame. Just needed to add a pair of 74LS670s as the 4 page registers. Moving to even the dumbest CPLDs would probably let me ditch the external page registers since I only need 4x8 bits of storage.)

    I still don't get why the Lo-Tech card doesn't work for you. What happens if you stick a VGA card into that machine and run one of those programs that uses VGA memory to bring the total up to 704k?
    Last edited by Eudimorphodon; October 19th, 2020 at 11:49 AM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  5. #25
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,083

    Default

    Quote Originally Posted by Trixter View Post
    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.)
    ... FWIW, I was poking around to see if I could find one of those VGA-to-memory programs to experiment with, and Google mentioned this thread that has a post in it where you say the Lo-Tech card actually works fine with "704k.com" and DOSes other than DR-DOS and PC-DOS 2000?

    EDIT: I'm just going to toss this dumb comment out there since I tracked down ADDMEM.EXE to test on my Tandy 1000(*) and it mentions a possible issue in its documentation. If you have an XTIDE card in this 5160, is it configured for "Full Operating Mode"? That mode grabs 1K under the top of RAM to do its thing, which I imagine would make it fundamentally incompatible with moving the top of memory. ADDMEM came with a device driver to relocate that if needed (apparently IBM PS/2s do that, among other things), although I suspect it won't stack well with 704k.com.

    (* I don't think I'll ever run addmem again because, ho boy, its Shareware nag may be the most intrusive thing I have ever seen, but it did work to give me a positively ridonkulous amount of conventional memory, 721K out of 736K, text only of course, under PC-DOS 2000.)
    Last edited by Eudimorphodon; October 19th, 2020 at 02:04 PM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  6. #26
    Join Date
    Sep 2020
    Location
    Wellington, New Zealand
    Posts
    42

    Default

    Since this thread has kind of derailed into a generic UMB discussion, here's what I am playing with on my XT:

    I have an SMC8003EP (aka WD8003EP) 8-bit Ethernet card in my XT, and whilst perusing the datasheet for the card's WD83C584 bus controller, noticed that it had a configuration register described as "indicates that a 32K RAM is installed in the ROM socket". And indeed, installing a CY62256 32K SRAM in the card's boot ROM socket and enabling that configuration bit works like a charm -- 32K of RAM appears at the configured boot ROM address!

  7. #27
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,083

    Default

    Quote Originally Posted by Eudimorphodon View Post
    If you have an XTIDE card in this 5160, is it configured for "Full Operating Mode"? That mode grabs 1K under the top of RAM to do its thing, which I imagine would make it fundamentally incompatible with moving the top of memory. ADDMEM came with a device driver to relocate that if needed (apparently IBM PS/2s do that, among other things), although I suspect it won't stack well with 704k.com.
    ... Blawblawjabberjabber to myself, but... an observation about this:

    If the problem *is* because the XTIDE is creating an extended BIOS area at the 639k mark then that would explain why QRAM might work anyway because QRAM has explicit support for moving an XBA if it finds one. (It's in the docs and enabled by default; for laughs I installed it to see what it does, had never touched it before.)

    I spent just a few minutes poking at QRAM, but unless there's something I'm missing about it it has an *extremely* unfortunate limitation: it apparently knows about and can use the "shadow ram" functionality of some 286 chipsets to fill in upper memory instead of/in addition to using LIM 4.0 hardware, but there doesn't seem to be any way to instruct it to use RAM that's statically already there. (IE, it can't substitute for USE!UMB.SYS or the like.) That's a genuine bummer/oversight, considering memory cards for PCs that could give you bonus memory above the 640k mark (like the Lo-Tech card) were a thing that existed back then. (IE, why 704k.com exists.) It was actually kind of a shock that Manifest didn't seem to have any idea how to look for unused memory in the upper memory map like, say, Check-it!, can. I vaguely remember the ads making it sound like Manifest was this amazing uber-tool that could ferret out what was lurking in every little nook and cranny...

    On the bright side its vidram.com TSR works under PC-DOS's memory management just fine on the VGA 1000 and gives me even more memory than Addmem did. 725K conventional!!!
    Last edited by Eudimorphodon; October 19th, 2020 at 03:07 PM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  8. #28
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    3,083

    Default

    Quote Originally Posted by kdr View Post
    I have an SMC8003EP (aka WD8003EP) 8-bit Ethernet card in my XT, and whilst perusing the datasheet for the card's WD83C584 bus controller, noticed that it had a configuration register described as "indicates that a 32K RAM is installed in the ROM socket". And indeed, installing a CY62256 32K SRAM in the card's boot ROM socket and enabling that configuration bit works like a charm -- 32K of RAM appears at the configured boot ROM address!
    NICE!

    I just took a look at the datasheet for the RealTek 8019AS in my machine and it looks like the same trick might be possible. The bit in question refers to "Flash Memory", but all it does is gate whether the MEMW pin is enabled on the socket so I can't think of a reason why it wouldn't take an SRAM.

    ... EDIT: On second thought, later in the manual it looks like "write enable" register might not have its state loaded from reading the EEPROM, enabling writes is something you'd have to do after power-on. So maybe if you wanted an SRAM in that socket you'd need to make a little device driver stub to throw the write enable at it before loading USE!UMB.SYS, which would sure be a pain. Not 100% sure, though...
    Last edited by Eudimorphodon; October 19th, 2020 at 04:14 PM.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  9. #29

    Default

    Quote Originally Posted by kdr View Post
    Since this thread has kind of derailed into a generic UMB discussion, here's what I am playing with on my XT:

    I have an SMC8003EP (aka WD8003EP) 8-bit Ethernet card in my XT, and whilst perusing the datasheet for the card's WD83C584 bus controller, noticed that it had a configuration register described as "indicates that a 32K RAM is installed in the ROM socket". And indeed, installing a CY62256 32K SRAM in the card's boot ROM socket and enabling that configuration bit works like a charm -- 32K of RAM appears at the configured boot ROM address!
    Holy crap that's awesome. Guess I need to upgrade to DOS 5 now for UMB support

  10. #30
    Join Date
    Sep 2020
    Location
    Wellington, New Zealand
    Posts
    42

    Default

    Quote Originally Posted by Eudimorphodon View Post
    I just took a look at the datasheet for the RealTek 8019AS in my machine and it looks like the same trick might be possible. The bit in question refers to "Flash Memory", but all it does is gate whether the MEMW pin is enabled on the socket so I can't think of a reason why it wouldn't take an SRAM.
    The 83C584 has separate bits for 'flash' and 'RAM', but I'm not sure what the exact difference might be...

    I intend to write a tiny little device driver that will twiddle the bits, because it appears that the RAM bit is in a register that isn't automatically loaded from the EEPROM at power on. I was stoked to discover that all I needed to get a bit of UMB was a $4 SRAM chip! I found this mostly by accident, because I was using the adapter's boot ROM socket to dump some video BIOS chips and needed to configure the correct ROM size...

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •