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Thread: IBM PC XT 5160 BIOS versions

  1. #1
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    Default IBM PC XT 5160 BIOS versions

    According to:
    1. Various editions of Upgrading & Repairing PC's (Scott Mueller)
    2. BIOS listing for 01/10/86 version
    3. ROMs in possession
    4. IBM's Technical Reference for the 5160
    5. Internet sources
    6. Contributions from forum members


    -------------------------
    08/16/82
    -------------------------
    Not much information on this BIOS.
    Mueller's 'Upgrading & Repairing PCs' book doesn't list it, but some other sources do.
    There is a dump of part of BIOS on the Internet. The date string within it is "08/16/82" and the copyright string within it is "5000026 COPR. IBM 1982"

    ROM SIZE = 40K
    ROM U18 = 32K chip labeled with IBM part number of 5000026
    ROM U19 = 8K chip labeled with IBM part number of 5000027 (reused in the next BIOS - dated 11/08/82)

    U18 contains the actual BIOS plus part of BASIC. U19 contains the remainder of BASIC.

    It is possible that this BIOS did not make it into the 5160s released to the public.
    If it did, there can't be too many about because this BIOS was replaced three months later (11/08/82).

    Question: Does the source code for it appear in the first edition of IBM's Technical Reference for the 5160?
    Question: Does anyone actually have a "5000026" stamped chip?


    -------------------------
    11/08/82
    -------------------------
    ROM U18 = 32K chip
    ROM U19 = 8K chip
    KNOWN ROM SETS = U18=1501512/U19=500027 or U18=1501512/U19=6359116
    ID/SUBMODEL/VERSION = FE/--/--
    * Used on 64/256K motherboards.
    * "The original XT BIOS had all of the features of the latest 10/27/82 PC BIOS."

    Memory map:
    . = unused
    b = ROM BASIC
    R = ROM BIOS
    ------: 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
    0F0000: ........................bbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbRRRRRRRR
    ------: ........................|< U19 >|<----------- U18 ------------->|


    -------------------------
    01/10/86
    -------------------------
    ROM SIZE = 64K
    ROM U18 = 32K chip
    ROM U19 = 32K chip
    KNOWN ROM SETS = U18=62X0851/U19=62X0854 (PROM) or U18=62X0852/U19=62X0853 (EPROM)
    ID/SUBMODEL/VERSION = FB/00/01
    * Used on 256/640K motherboards. Up to 640K RAM.
    * Enhanced POST (one known enhancement is a faster test of RAM).
    * Added support for the 101-key Enhanced keyboard.
    * Support for 720K floppy drives. Support for 1.2M floppy drives.

    Memory map:
    . = unused
    b = ROM BASIC
    R = ROM BIOS
    ------: 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
    0F0000: RRRRRRRRRRRRRRRRRRRRRRRRbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbRRRRRRRR
    ------: |<----------- U19 ------------->|<----------- U18 ------------->|


    -------------------------
    05/09/86
    -------------------------
    ROM SIZE = 64K
    ROM U18 = 32K chip
    ROM U19 = 32K chip
    KNOWN ROM SETS = U18=59x7268/U19=62x0819 (EPROM) or U18=62x0890/U19=68x4370 (PROM)
    ID/SUBMODEL/VERSION = FB/00/02
    * Contained some fixes for minor keyboard bugs related mainly to the enhanced keyboard.

    Memory map:
    . = unused
    b = ROM BASIC
    R = ROM BIOS
    ------: 0---1---2---3---4---5---6---7---8---9---A---B---C---D---E---F---
    0F0000: RRRRRRRRRRRRRRRRRRRRRRRRbbbbbbbbbbbbbbbbbbbbbbbbbb bbbbbbRRRRRRRR
    ------: |<----------- U19 ------------->|<----------- U18 ------------->|

    Last edited by modem7; October 23rd, 2009 at 10:04 PM. Reason: Marked the 62X0852/62X0853 set as 'EPROM'

  2. #2

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    Quote Originally Posted by modem7 View Post
    According to:
    * The original XT BIOS had all of the features of the latest 10/27/82 PC BIOS.
    The XT BIOS doesn't have the cassette I/O support that the PC BIOS has.

    Quote Originally Posted by modem7 View Post
    According to:
    ROM U19 = 4K chip labeled with IBM part number of 5000027
    It's actually 8K I think...
    Last edited by per; February 15th, 2008 at 10:55 AM.

  3. #3

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    Quote Originally Posted by per View Post
    The XT BIOS doesn't have the cassette I/O support that the PC BIOS has.
    It's actually 8K I think...
    Although technically correct I always thought each ROM was 4k and since IBM had a HI & LOW rom you ended up with 8k total between the 2.

  4. #4
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    Default

    The XT BIOS doesn't have the cassette I/O support that the PC BIOS has.
    "The original XT BIOS had all of the features of the latest 10/27/82 PC BIOS" is a quote from the 8th edition (and others) of Mueller's 'Upgrading & Repairing PCs'.
    One mustn't read too much into that. So I wouldn't expect cassette support to be in an 5160 BIOS because the 5160 lacks cassette hardware.
    Likewise, I wouldn't expect to see any code that attempts to read two switch blocks.

    It's actually 8K I think
    40-32=8 How did I end up with 4 ? I've just replaced the batteries in my calculator, so it doesn't happen again.
    Thanks for picking up my mistake. I've corrected the post.

  5. #5
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    Default

    Although technically correct I always thought each ROM was 4k and since IBM had a HI & LOW rom you ended up with 8k total between the 2.
    You're thinking of the AT. Two ROMs each supplying 8 data bits for a 16 bit data bus.

  6. #6

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    Quote Originally Posted by modem7 View Post
    According to:
    -------------------------
    01/10/86
    -------------------------
    ROM SIZE = 64K
    ROM U18 = 32K chip labeled with IBM part number of 62X0851
    ROM U19 = 32K chip labeled with IBM part number of 62X0854
    In case you're interested in another data point, I have a motherboard with
    62X0852.U18 and 62X0853.U19. But their contents are the same as the ones
    listed in your post for 10JAN86.

    Bill
    Last edited by wrljet; May 23rd, 2010 at 09:59 AM. Reason: typo misspelling

  7. #7
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    Default

    Thank you Bill for your contribution. I've amended the first post.

  8. #8

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    Quote Originally Posted by wrljet View Post
    In case you're interested in another data point, I have a motherboard with
    62X0852.U18 and 62X0853.U19. But their contents are the same as the ones
    listed in your post fr 10JAN86.

    Bill
    Are the checksums of the contents (and not just the bios date) the same as the other ones?
    CRC32 Checksums should be:
    62x0851 = 1054f7bd
    62x0854 = b5fb0e83

    If the checksums are not the same, I'd be interested in seeing what the differences are.

    LN

  9. #9

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    Quote Originally Posted by Lord Nightmare View Post
    Are the checksums of the contents (and not just the bios date) the same as the other ones?
    CRC32 Checksums should be:
    62x0851 = 1054f7bd
    62x0854 = b5fb0e83

    If the checksums are not the same, I'd be interested in seeing what the differences are.

    LN
    The entire contents of the ROMs are identical, byte for byte.

    Bill

  10. #10
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    Default

    All models of the XT use the same basic board. You can upgrade from a 11/08/82 to a 05/09/86 BIOS merely by replacing the ROMS/EPROMS. This would suggest that the U19 ROM/EPROM is actually a 32K chip with only 8K used. Otherwise, how does the board deal with the two extra address lines when an 8K chip is installed?

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