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Thread: HIMEMV2 or equivillent PROM

  1. #1
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    Default HIMEMV2 or equivillent PROM

    If your not familiar with the HIGHMEMV2, see the folowing 1megXT.txt.It is a chip that replaces the rom in socket u44 on the IBM 5160 XT Motherboard to address memory up to 1 meg. I did the mod for 640KB on the motherboard about 25 years ago. So I have 256k chips in banks 0 and 1. I have enough 256k chips that I pulled from another board to fill the other two banks. I realize that the added memory will only give me about 64k of Contiguous base memory, but I believe there is a good size chunk of other unused memory between 640K and 1 Meg that could be used as UMB to load device drivers like Network drivers etc. using something like Quarterdeck Cram.
    Chuck(G) had mentioned using a GAL to replace the rom, but I don't have the technical expertise to burn one properly. I'd be willing to pay for the chip plus shipping and any other costs incurred (within reason of coarse). I had also hi-jacked a thread in PC's AND CLONES that discussed this same topic, but that thread has gotten a little long and has not attracted much interest lately, so I decided a new thread here might get the right person or persons interested. Anyone willing to help me with this project, please PM me or E-mail me at gregsaling@comcast.net

  2. #2
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    No takers yet?
    Maybe I can make things more interesting? I've got some old parts that I might be willing to trade. For example, I have a IBM 5160 case with a power supply. I also have an IBM CGA Card, a 1.2 meg 5-1/4 floppy drive. I'm sure there are people out there with the skills required. I just haven't made things attractive enough!!

    Regards,

    Greg

  3. #3
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    Quote Originally Posted by ibmapc View Post
    I'm sure there are people out there with the skills required.
    Yeah, but I think there's only a few of them (and they don't include me).

  4. #4
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    Tell you what. I'll burn a 20-pin GAL and indicate what pins are what--you make up an adapter to fit the 16-pin existing PROM socket. 82S23 PROMs are very hard to come by nowadays--just ask any of the arcade gamers. A GAL would do the job easily.

    I can provide the GAL in DIP or 20-pin PLCC, which is quite tiny--you could even make up a small PCB with pins to fit a 16-pin DIP socket and stick the PLCC on it.

    But I don't have a genuine 5160 any more, so all I have is the document you've cited to work from--I think I understand it.

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    Awsome, thanks for taking time to help me with this project. I was thinking that a 20 pin dip would be pretty easy to adapt to the 16 pin socket if most of the pins line up by modifying a 20 pin socket (I work as a machinest and can modify small parts at work if necessary). However, if you think the PLCC would be a better way to go then I'll have to learn how to make up a PCB. Let me know what you think.

    Thanks for your help.

    Greg

  6. #6
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    It doesn't really matter to me--they program the same way. I think I can get most of the pins to line up--let me play around a bit. At least most of the address lines are on the left side and the data output lines are on the right side of the 82S23, so it's not beyond hope that we'll get at least most of them to line up.

  7. #7

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    Quote Originally Posted by Chuck(G) View Post
    It doesn't really matter to me--they program the same way. I think I can get most of the pins to line up--let me play around a bit. At least most of the address lines are on the left side and the data output lines are on the right side of the 82S23, so it's not beyond hope that we'll get at least most of them to line up.
    Actually only 3 of the 4 data lines are used, and each configuration is only 16 words, so a 16x3bit memory would be enough to store a single desired configuration. However, then switches 3/4 and jumper E2 won't do anything.

    Two of the data lines will select the bank number, and the third data line just enables the bank sellected. Here is a thruth table:
    Code:
    D3
    |D2
    ||D1
    |||D0
    ||||
    vvvv
    xxx0 = Segment not mapped to any RAM bank
    x001 = Segment mapped to RAM bank 0
    x011 = Segment mapped to RAM bank 1
    x101 = Segment mapped to RAM bank 2
    x111 = Segment mapped to RAM bank 3
    The segment number is presented directly on A0-A3 of U44, where the rest of the Ax lines are connected to switches 3/4 and jumper E2 (as a way to select between up to 16 different configurations).
    Current systems owned by me:
    Vintage:IBM PC/XT submodel 087 ( 1983 ), [Kon]tiki-100 rev. C (1983), Compaq Portable I ( 1984 ), IBM PC/XT submodel 078 ( 1985 ), IBM PC/XT286 ( ~1986 ), 3x Nintendo Entertainement Systems ( 1987 ).
    Obsolete:Commodore A500 ( ~1990 ), IBM PS/2 model 70/386 type 8570-161 ( 1991 ), Atari Lynx II ( ~1992 ), Generic Intel 486SX PC ( ~1993 ), AT/T Globalyst Pentium w/FDIV bug MB ( 1994 ), Compaq 486DX4 laptop ( ~1995 ).

  8. #8
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    In any case, Greg, you can do me a great favor by transcribing the data from the document into a 16 row by 16 column simple text file.

    In other words, consider the HIMEMV2 ROM as described:

    Code:
                            HIMEMV2 U44 DECODER PROM PROGRAM
    
         BOTH JUMPERS INSTALLED
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
          Seg# >>>=====>  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
         (4 banks of  0 = 9  9  9  9  B  B  B  B  D  D  D  D  F  F  F  E  = 928K
         256K chips)  1 = 9  9  9  9  B  B  B  B  D  D  D  D  E  F  F  E  = 864K
                      2 = 9  9  9  9  B  B  B  B  D  D  D  D  E  E  F  E  = 800K
                      3 = 9  9  9  9  B  B  B  B  D  D  D  D  E  F  E  E  = 800K
    
         E2 JUMPER 3 to 4 ONLY
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
          Seg# >>>=====>  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
         (Misc.       4 = F  F  F  F  D  D  D  D  B  B  B  E  9  9  9  E  = 896K
         arrangements)5 = F  F  F  F  D  D  D  D  B  B  B  E  E  E  E  E  = 704K
                      6 = 9  9  9  9  B  B  B  B  D  F  E  E  E  E  E  E  = 640K
                      7 = 9  B  D  F  E  E  E  E  E  E  E  E  E  E  E  E  = 256K
    
         E2 JUMPER 1 to 2 ONLY
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
          Seg# >>>=====>  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
         (Up to 4     8 = 9  9  9  9  B  B  B  B  D  D  F  E  F  F  D  E  = 896K
         banks of     9 = 9  9  9  9  B  B  B  B  D  D  F  E  E  F  D  E  = 832K
         256K chips)  A = 9  9  9  9  B  B  B  B  D  D  E  E  F  F  D  E  = 832K
                      B = 9  9  9  9  B  B  B  B  D  D  E  E  E  F  D  E  = 768K
    
         NO JUMPERS INSTALLED
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
          Seg# >>>=====>  0  1  2  3  4  5  6  7  8  9  A  B  C  D  E  F
                          =  =  =  =  =  =  =  =  =  =  =  =  =  =  =  =
         (Up to 3     C = B  B  B  B  D  D  D  D  F  F  E  E  E  9  F  E  = 768K
         banks of     D = B  B  B  B  D  D  D  D  F  F  F  E  E  9  E  E  = 768K
         256K and     E = 9  B  B  B  B  D  D  D  D  F  E  E  E  E  E  E  = 640K
         1 of 64K)    F = 9  B  B  B  B  D  F  E  E  E  E  E  E  E  E  E  = 448K
    Go down each of 16 columns and invert (rows to columns and vice-versa) the arrangement. So, for the first row, we'd go down the entire 0 column and write:

    9999FF999999BB99

    The second row would be:

    9999FF9B9999BBBB

    and so on, for 16 rows. It would save time for me, particularly if you double-checked your copy.

    If you wanted to put some icing on the cake, you could do the same for the original table as described in the document.

  9. #9
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    OK I'm workin on it. Should be done shortly.

  10. #10
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    Quote Originally Posted by ibmapc View Post
    OK I'm workin on it. Should be done shortly.
    Copy & paste into a spreadsheet, sort to remove garbage, and transpose.

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