IBM PC diagnostics disks

Jay Jaeger cube1 at
Mon Aug 16 16:57:15 CDT 2021

On 8/10/2021 10:30 PM, Jay Jaeger via cctech wrote:
> On 7/29/2021 1:22 PM, Mark Huffstutter via cctech wrote:
>> Yes, I sadly, learned that important lesson years ago, after finding My
>> "Original" Original PC DOS diskette set pretty much destroyed, left in
>> The folders in storage for too long.....
>> -----Original Message-----
>> From: cctalk [mailto:cctalk-bounces at] On Behalf Of Al 
>> Kossow via cctalk
>> Sent: Thursday, July 29, 2021 10:15 AM
>> To: cctalk at
>> Subject: Re: IBM PC diagnostics disks
>> On 7/29/21 10:08 AM, Mark Huffstutter via cctalk wrote:
>>> Hi Richard,
>>>                      I could use them if they are still available, I 
>>> have the very nice binder manual for them, minus the disks!
>> Don't store diskettes in vinyl sleeves.
>> The plasticiser leaches out of the vinyl onto the surface of the 
>> diskettes.
> Interesting. The IBM ones that I have had in the clear 5 x 8.5 vinyl 
> sleeves were in their paper-like material sleeves inside the vinyl. They 
> have been mostly just fine - just read them in this past week.
> On the other hand maybe 10% or so of my 3B2 floppies that were similarly 
> stored, but in a somewhat different form of vinyl had more sector 
> errors.  Fortunately I copied some of them (the most critical ones) some 
> time ago, and those were stored separately, so I expect those will be 
> fine, but I haven't yet read them in.

Correction:  Out of  49 AT&T floppies that were in their paper envelopes 
inside vinyl exactly ONE turned out to actually be bad - and it had been 
bad many years ago (1997) when I got them.  So, to date I have not 
experienced any issues with vinyl holders - so long as the floppy is in 
its paper sleeve, at least.

The problem I actually discovered this week that I was not reading the 
3B2 floppies on a 96 TPI drive (they are 512 byte sectors, 80 tracks, 
two sides, 9 sectors "quad" density.)  Once I figured that out, all but 
the one read just fine.   On the other hand, several copies I made on a 
PC floppy drive (I think) back when were mostly bad (either that, or I 
made them on the 3B2, but used HD media, perhaps).

One final note:  why do I re-image stuff using different techniques? 
Well, here is a case in point.  The images that (I believe) I had made 
of these floppies in 1997 - I think using dd on the 3b2 itself to files 
on the hard disk, and then transferred using zmodem to my PC - were all 
ONE TRACK SHORT.  Now, there is a pretty good chance that that last 
track on most of those floppies didn't have any real data - but one 
never knows.  I did verify that the first 79 tracks of those images, and 
those I made the past couple of days were the same.

Using my new greaseweazle I have verified that images I made of PC 
floppies of various sorts (160, 360, 720, 1.2M (including RT/PC), 
1.44M), RX50 were all just fine.  Only the 3B2 images were off.


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