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Thread: MR-BIOS implementation in a 128KB BIOS image for a Packard Bell PB450 motherboard

  1. #1
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    SE Michigan, USA
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    Default MR-BIOS implementation in a 128KB BIOS image for a Packard Bell PB450 motherboard

    I have no idea if this is possible or not, however, is there a way and is somebody willing to implement the MR-BIOS for a Packard Bell PB450 motherboard that has an OPTi 82C895 chipset, Cirrus Logic CL-GD5428 video?

    Here's the dumped standard BIOS image when I archived the chip a couple of months ago: https://drive.google.com/open?id=1P0...c_vI5QUEmjyb94 (128KB)

    And for the 82C895 MR-BIOS: http://www.mediafire.com/file/49pbet...-BIOS_v202.zip <-- link from: https://www.vogons.org/viewtopic.php...=59146#p658582 & http://www.vcfed.org/forum/showthrea...385#post506385 (64KB)

    The video BIOS is implemented in the chip itself and I cannot find any resources or know which lines to copy over from the 82C895 MR-BIOS image to the Packard Bell BIOS image.
    Current retro systems:
    2x Commodore 64 Breadbin 250407 Rev. B and C
    Packard Bell Pack-Mate 28 Plus, aka, the Ultimate Sound Card machine
    iMac G3/600 Graphite, Mac OS X 10.4.11 Tiger, Lubuntu 16.04.3 LTS
    iMac G4/800 Lampshade, Mac OS X 10.4.11 Tiger
    YouTube channel: https://www.youtube.com/c/RetroPCUser

  2. #2

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    I already successfully splittet a VGA BIOS from SYSTEM BIOS on an NCR 386 and used two chips in the end. But this is years ago and I dont remember the details. I'll try with IDA look at it.

    Hopefully everything is "pretty standard", this would mean, lower 64k VIDEO bios, upper 64k SYSTEM BIOS. There must be some address decodinng logic to react on C000 segment for video bios and F000 segment for system BIOS.

    Try opening the file in a hex editor and look for strings.

    Do you have a EPROM burner and are you willing to do a few tries if I try to assemble the two images? I cant say for sure it will work. Maybe you have to revert to original.

  3. #3

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    Maybe I got it wrong. English is not my native language and sometimes I understand wrong.

    I got this to my mind: You have a ROM chip that holds VIDEO and SYSTEM bios. You want to change the VIDEO BIOS to another one.

    After a second read I am not sure anymore if I got it right. Changing the Video BIOS is possible. The system bios most likely not.

  4. #4
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    I do have an (E)EPROM programming tool and software that can read and write to my Packard Bell's BIOS chip with success. Good thing I dumped the BIOS onto my computer in case anyone needed it. Also, it's just only the one BIOS chip that has the video and system BIOS, and I'm willing to do a few attempts to see how it works and report back.
    Current retro systems:
    2x Commodore 64 Breadbin 250407 Rev. B and C
    Packard Bell Pack-Mate 28 Plus, aka, the Ultimate Sound Card machine
    iMac G3/600 Graphite, Mac OS X 10.4.11 Tiger, Lubuntu 16.04.3 LTS
    iMac G4/800 Lampshade, Mac OS X 10.4.11 Tiger
    YouTube channel: https://www.youtube.com/c/RetroPCUser

  5. #5

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    Ok, but I still need some clarification Do you want to replace the system bios in that chip or the video bios? Video is possible, system most likely not.

  6. #6
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    The system BIOS in the chip itself. I sure as heck wish I can put the video BIOS on a separate spot, such as, my network card, but, that'll be impossible since the BIOS itself is 64KB and my network card only supports up to 32KB (E)EPROM chips.
    Last edited by retro-pc_user; November 5th, 2018 at 01:29 PM.
    Current retro systems:
    2x Commodore 64 Breadbin 250407 Rev. B and C
    Packard Bell Pack-Mate 28 Plus, aka, the Ultimate Sound Card machine
    iMac G3/600 Graphite, Mac OS X 10.4.11 Tiger, Lubuntu 16.04.3 LTS
    iMac G4/800 Lampshade, Mac OS X 10.4.11 Tiger
    YouTube channel: https://www.youtube.com/c/RetroPCUser

  7. #7

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    I am not totally sure, but as Video BIOSes are usually at C000 segment, I think they dont support other load segments. Also, for the same reasons, I dont think network cards support mapping a ROM at C000.
    I have soldered 2x32k flash chips to a piece of veroboard and soldered wires directly at the original socket back when I splitted up that NCR system ROM.

  8. #8

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    I am 80% sure another system bios will not work. But let's give it a try.
    I've ran this through IDA's auto-analyze, but totally like expected, auto analyze gives me garbage in terms of what it is declaring as data, code, ...
    It says ~90% of the image is data, this could be, but is verly unlikely, that a BIOS+VIDEO_BIOS only take 12k.

    Next step, looked for strings. It looks like that the VIDEO BIOS is before the SYSTEM bios.

    Next step, I searched for x86 reset vectors. They are not there, where I expect them. This is why I don't trust me, having em found. Dead end.

    Next step, I converted the whole image you have uploaded to a picture, rendering it as 8bit wide font (x size = 8, fits for 8x8 8x14 and 8x16).
    This showed up two times the same charset, so no further clue from this...01-00200.jpg

    Before I go back to IDA i want you to do one more thing.
    Use "ree" (I attached, "rom extension extractor") to get the two images from the place where they are mapped (usually 0xC0000 and 0xF0000).
    Once I have these two extracted images I should easily be able to locate offset in your 128k-image. Once we have the storage-addresses and sizes we can easily put another BIOS into that place that fits and try on your machine.

    You start ree.exe, it beeps and shows some ASCII chars and most likely finds a video bios at C0000 in the beginning. It asks wheter to extract or not - extract.
    He runs more addresses to search, but does not extract SYSTEM BIOS by default.
    This is done by "ree /sys". You end up with C000.ROM and F000.ROM. These two files I need.
    ree.zip

  9. #9
    Join Date
    Oct 2017
    Location
    SE Michigan, USA
    Posts
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    I will run this program once I'm done with my errands and fixing the battery holder I soldered onto the motherboard with a new one.
    Current retro systems:
    2x Commodore 64 Breadbin 250407 Rev. B and C
    Packard Bell Pack-Mate 28 Plus, aka, the Ultimate Sound Card machine
    iMac G3/600 Graphite, Mac OS X 10.4.11 Tiger, Lubuntu 16.04.3 LTS
    iMac G4/800 Lampshade, Mac OS X 10.4.11 Tiger
    YouTube channel: https://www.youtube.com/c/RetroPCUser

  10. #10
    Join Date
    Oct 2017
    Location
    SE Michigan, USA
    Posts
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    I have gotten the video BIOS and system BIOS info as promised. I have the zip file attached and it's also on my Google Drive as well: https://drive.google.com/open?id=1ne...7usY7OSFZzHM7U
    Attached Files Attached Files
    Current retro systems:
    2x Commodore 64 Breadbin 250407 Rev. B and C
    Packard Bell Pack-Mate 28 Plus, aka, the Ultimate Sound Card machine
    iMac G3/600 Graphite, Mac OS X 10.4.11 Tiger, Lubuntu 16.04.3 LTS
    iMac G4/800 Lampshade, Mac OS X 10.4.11 Tiger
    YouTube channel: https://www.youtube.com/c/RetroPCUser

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