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Thread: Shugart SA-455 compatible with PCs?

  1. #1
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    Default Shugart SA-455 compatible with PCs?

    I was trying to divine this from the manual but it wasn't clear to me. I have a 360k SA-455. I'm planning to get a couple more for a Mindset expansion unit, but would like to test them on one of my bench PCs first. Is it safe to assume the edge connector on these has the same pinout as generic PCs? From what I've read these drives were intended for PC compatible applications, and I know now they were used in computers like the Mindset, but a lot of these computers are 'compatible-ish' and I wouldn't assume they follow standards precisely.

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    It should work; just remember to set the drive-select jumper correctly. Bitsavers has dox.

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    Yup. I've used one in my 5155, for testing purposes. I believe the SA-455 handles pin 34 more "correctly" than the drive that came with the 5155. Pin 34 on the Qume that came in the Portable must be disconnected when used on a High Density controller in conjunction with a High density drive. But that wasn't necessary on the Shugart. SEE HERE if interested.

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    Should be fine. Per Chuck's comment the question would really be whether the Mindset replicates the IBM's off-spec way of doing drive select and motor control or does it the standard Shugart way. Broadly speaking most drives should work fine in a PC and it's twisted-cable method of drive select if you set them to drive 1. (IE, second drive, not drive 0.) If the Mindset doesn't have any twists in the cable then I'd assume it will want them jumpered as 0 and 1.

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    The Mindset actually has two edge connectors on the controller board it looks like: http://old-computers.com/museum/phot...eFDunit_s1.jpg One for each drive rather than the drives being chained together on one cable.

    That was what tipped me off to it perhaps being unusual.

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    Do you have a complete Mindset expansion unit with drives so you can see how they're jumpered and wired? There are certainly exceptions to the rule that a 34-pin connector means according-to-Hoyle Shugart compatible. Worst case the original drives could have had custom driver boards sitting on the mechanism, in which case all bets are off.

    (A not insignificant number of companies did order drives with cute customization options like carrying power to the drive over otherwise unused pins on the 34 pin card edge. Later Tandy 1000s, some Amstrad machines, Osbornes....)

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    No I was thinking about buying one sans drives that an ebay seller has. I'm amazed at how few interior pics of the machine are online. And yeah, I ran into the customization thing headfirst. The spare 455 I have here has a working bottom end, I was going to swap the PCB from the B drive in my MD3, which had the spindle motor quit. But it didnt work with the board swap and even managed to gouge a disk in the process.

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    The problem with using non SA-455 drives is that I think the faceplate for the unit is configured to work only with the SA-45x drives. I seem to have run down this issue some time in the past.

  9. #9

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    I just looked up the pin locations for the SA455. I believe the twist lead for a PC connects the motor on and the desired drive select. Both drives would then have the same drive select jumper and work with a twist cable. Looking at the SA455 specification, that would be drive select 2. They are numbered 1 2 3 and 4, not 0, 1, 2 and 3, on the SA455. So I believe to work with a twist cable, you'd jumper DS2 and not DS1.
    Dwight

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    I apologize for any confusion about the DS numbering. The Gotek I have sitting on my desk it has the select jumpers labeled "0" and "1" which I also dimly recall being the case on some other older floppy drives but that apparently isn't universal. In any case, the important thing is you want it configured as the second, not first, position...

    For a PC, anyway. No idea about a Mindset. I looked up the auction on eBay and it at least does look like it uses Molex connectors for power... probably? Technically the one picture that would settle the question has the plugs kind of out of view.

    (Personally I don't think I'd touch that auction with a ten meter cattle prod, but...)

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