Re: Need an 8280 formatted 8" disk (progress!)

From: Mike Stein <>
Date: Wed, 15 Feb 2017 15:30:00 -0500
Message-ID: <AC50CF55D94E41FDAAB40A79B6B24DA5@310e2>
Hi Bo and all,

I don't have an 8280 so I was confused; this entry on your site suggests that it uses the TM-848-1 with single-sided SS/DD disks:

whereas pretty well everything else suggests that it uses the double-sided TM848-2 with double-sided disks (DS/DD or 2S/2D), so I assume that that is indeed what it uses.

Also, there are a number of references to a (direct drive LSI) TM848-E but the picture on Andre's site is of a substantially different (belt drive) TM848; were both versions used?

Do we know definitely which model the drives in an 8280 really are?

As mentioned previously the disks only have one index hole, but its location is slightly different depending on whether the disk is single-or double-sided.

A double-sided drive can read both SS and DS disks but it is certainly aware of what type is inserted; there is also an optional signal on pin 10 that informs the controller, so it's quite possible that trying to select side 1 on a single-sided disk will fail.

So, if the 8280 indeed uses double-sided double density disks, than that is what you should use. ;-)


----- Original Message ----- 
From: "Bo Zimmerman" <>
To: <>
Sent: Wednesday, February 15, 2017 2:20 PM
Subject: Re: Need an 8280 formatted 8" disk (progress!)

> Hey Rob, all
> I've also had a formatting problem with my 8280, but haven't tried it 
> out again in a decade.  I recall, like you, going on an intense hunt for 
> the Correct floppy disks.  I ended up with a box of Verbatum 2s/2d 
> soft-sectored "FD2" disks from 1990 (!!)
> The 2S/2D disk I have has a single round hole near the center that goes 
> clear though the disk, but no second hole (unless you count the fact 
> that the same hole is on both sides of the disk).
> The disk also has a write-protect tab on the bottom-right of the disk, 
> near where the read/write exposure strip is.  Came right out of the damn 
> box that way.  Could the write-protect logic on 8" disks be opposite to 
> 5.25"? That is, write is enabled when the tab is covered, and disabled 
> when exposed?
> - Bo
> P.S. I never thought about issueing block read/write commands to an 
> unformatted floppy, since I just assumed that they would error out, but 
> that sounds like a fun thing to try, so thanks for that.
> On 2/13/2017 3:49 PM, Rob Clarke wrote:
>> Some progress has been made.  Thanks to Ethan's suggestion of trying
>> B-R and B-W to check the stepper operation I realised that track 0,
>> sectors 1-26 are readable and writable successfully, which shows that
>> all the read/write circuitry is good, as is at least side of my media.
>> It also shows that my attempts to format the disks at least started
>> successfully.
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Received on 2017-02-15 21:00:03

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