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  • iomega's oddball "SCSI-but-crippled" PC4B/50 MCA SCSI controller

    From [email protected]@21:1/5 to All on Sat Jun 4 13:07:12 2022
    Hi folks, I'm cross-posting this from the CSIPH FB group, as I'm not a huge fan of Facebook for long-form discussion.

    I recently picked up _eight_ of these iomega PC4B50 MCA cards. They're in excellent condition, but very poorly documented in the modern era. Has anyone personally ever used one of these, back in the day? They're circa-1989, and I'd like to offer anybody
    who wants one a crack at getting these to work with a modern SCSI emulation adapter, such as ZuluSCSI, SCSI2SD, or other such SCSI-2 compliant SCSI emulator.

    Since these SCSI emulators have user-configurable device, manufacturer, and version ID strings, it should be possible to lie to the HBA about it being one or more of the supported model types.

    According to the available documentation at ardent-tool, "The PC4B controller supports the following Iomega drive subsystems: Bernoulli 230, MultiDisk 150, Bernoulli 90, Bernoulli 44, Bernoulli, Floptical 21, LaserSafe, and LaserSafe PRO"

    The only device on the list above that I have currently is the MultiDisk 150, so that's where I'll start. Short of removing the MultiDisk 150 from its external enclosure, however, I can't easily attach it to the rear-facing DB37 connector, without
    fashioning my own cable, which is a PITA.

    As there are seemingly no high-quality photos of the card, I took a couple, one of the top of the PCB, and another of the bottom, which you can see here:

    Top - https://i.imgur.com/YSSciNw.jpg
    Bottom - https://i.imgur.com/v976U07.jpg

    I'm guessing that the NCR IC at U7, which is labeled 0114800, is a custom variant of a standard NCR SCSI controller, such as the 53C400, but that's just an educated guess.

    Regards,
    Alex Perez

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  • From Louis Ohland@21:1/5 to [email protected] on Sat Jun 4 16:07:11 2022
    Looks to be J6 / CR1 provides TERMPWR.

    Anyone got the BIOS? 27C64A-25, nothing special.


    On 6/4/2022 15:07, [email protected] wrote:
    Top -https://i.imgur.com/YSSciNw.jpg

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  • From [email protected]@21:1/5 to Louis Ohland on Sun Jun 5 10:09:37 2022
    On Saturday, June 4, 2022 at 2:07:27 PM UTC-7, Louis Ohland wrote:
    Looks to be J6 / CR1 provides TERMPWR.

    Anyone got the BIOS? 27C64A-25, nothing special.

    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

    --- SoupGate-Win32 v1.05
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  • From Louis Ohland@21:1/5 to [email protected] on Sun Jun 5 12:35:04 2022
    Huh, what? EEPROMs or OTPs, that would be sordid understandable.

    Can you provide the dump to MAJ Tom or "The Beem[er]"

    On 6/5/2022 12:09, [email protected] wrote:
    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

    --- SoupGate-Win32 v1.05
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  • From [email protected]@21:1/5 to Louis Ohland on Sun Jun 5 16:04:36 2022
    On Sunday, June 5, 2022 at 10:35:07 AM UTC-7, Louis Ohland wrote:
    Huh, what? EEPROMs or OTPs, that would be sordid understandable.

    Can you provide the dump to MAJ Tom or "The Beem[er]"
    On 6/5/2022 12:09, Alex Perez wrote:
    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.

    I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

    --- SoupGate-Win32 v1.05
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  • From Louis Ohland@21:1/5 to IBMMuseum on Mon Jun 6 19:55:49 2022
    Dave, how could Iomega restrict the PC4B to [I assume] removable drives?
    FUD, or just missing SCSI commands?

    On 6/6/2022 19:25, IBMMuseum wrote:
    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
    I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

    Looks fine to me - I'll compare the version to what I have.

    --- SoupGate-Win32 v1.05
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  • From [email protected]@21:1/5 to Louis Ohland on Mon Jun 6 18:08:23 2022
    On Monday, June 6, 2022 at 5:55:53 PM UTC-7, Louis Ohland wrote:
    Dave, how could Iomega restrict the PC4B to [I assume] removable drives? FUD, or just missing SCSI commands?
    On 6/6/2022 19:25, IBMMuseum wrote:
    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
    I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

    Looks fine to me - I'll compare the version to what I have.

    The easiest place to do this would probably be in the driver, but given that it appears they're using a custom ASIC, possibly just a customized PLCC 53C400 (It's NCR-branded, after all) the controller itself could easily limit it to working with a
    whitelist of SCSI devices, which only return approved SCSI device/vendor/versions strings, and possibly also a custom SCSI Mode Page.

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  • From IBMMuseum@21:1/5 to All on Mon Jun 6 17:25:59 2022
    I dumped it myself, but all but the first few bytes seem to be obfuscated in some way.
    I stuck it at http://scsi2sd.com/iomega-pc4b50-v6.21-rom.bin

    Looks fine to me - I'll compare the version to what I have.

    --- SoupGate-Win32 v1.05
    * Origin: fsxNet Usenet Gateway (21:1/5)
  • From IBMMuseum@21:1/5 to All on Mon Jun 6 20:38:29 2022
    I've got an earlier 'PC4' (no 'B') as well - with no ROM.

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  • From Louis Ohland@21:1/5 to IBMMuseum on Tue Jun 7 06:08:38 2022
    There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy failed.
    IA picks up www.iomega.com late '96 [IIRC], by then the PC4n was no
    longer active? can't see it in the Products section...

    On 6/6/2022 22:38, IBMMuseum wrote:
    I've got an earlier 'PC4' (no 'B') as well - with no ROM.

    --- SoupGate-Win32 v1.05
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  • From Louis Ohland@21:1/5 to Louis Ohland on Tue Jun 7 06:15:52 2022
    PC3B XT / AT
    PC4B 50 / 60 / 80

    On 6/7/2022 06:08, Louis Ohland wrote:
    There seems to be PC4, PC4A, PC4B. My attempts to dig up ad copy failed.
    IA picks up www.iomega.com late '96 [IIRC], by then the PC4n was no
    longer active? can't see it in the Products section...

    On 6/6/2022 22:38, IBMMuseum wrote:
    I've got an earlier 'PC4' (no 'B') as well - with no ROM.


    --- SoupGate-Win32 v1.05
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