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

From: Rob Clarke <>
Date: Mon, 13 Feb 2017 22:49:06 +0100
Message-ID: <>
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.

If I understand the sector numbering scheme correctly, side 0 has 
sectors 1-26 and side 1 has sectors 33-58. I can't read anything from 
track 0, sector 33 (26-32 give illegal T/S errors), so it looks like it 
gave up once we reached side 1. Now I understand a bit about the 8" 
formats, it's clear that my disks are officially single sided, but 
looking at the schematic for the 848-2 on zimmers, it has both index 
hole sensors, but I am not sure whether the signalling from the logic is 
equal, so maybe this is the issue?

My next plan is to cut an extra index hole to make it look like a double 
sided disk, has anyone got one to hand who can measure the offset of the 
index hole for me?

cheers, Rob

On 13/02/2017 19:04, Rob Clarke wrote:
> Ahh, now - the disks I have only has a single index hole - maybe this 
> is the issue? Maybe there was some extra setting to format single sided?
> On 13/02/2017 18:43, Mike Stein wrote:
>> Hi Rob,
>> Can't help you with a formatted disk but if you have trouble finding 
>> blanks once you get things sorted, let me know.
>> Note that single and double-sided disks have the index hole in 
>> different locations; most double-sided drives including the TM-848 
>> have two sensors and can use both types, but it's something to keep 
>> in mind just in case.
>> m
>> ----- Original Message -----
>> From: "Rob Clarke" <>
>> To: <>
>> Sent: Monday, February 13, 2017 7:54 AM
>> Subject: Need an 8280 formatted 8" disk
>>> Gents,
>>> I'm desperately in need of a known good 8" floppy formatted on an 8280.
>>> After 18 months of occasional work, I now have my 8280 up and running,
>>> or at least I think I do. DOS board is up and running, the drives are
>>> refurbished and behaving, and I have a good power source. I can trace
>>> signals all the way from the FDC to the read/write heads and back 
>>> again.
>>> Nevertheless, using the 2 no-name 8" disks I have, the format fails 
>>> with
>>> an error 21 on track 0, sector 1 every time. So, to track the fault 
>>> down
>>> it would really help to have a good disk. Either I can post one of my
>>> disks to someone or, if you hace a spare 8" disk, I'd gladly compensate
>>> for that and time, postage etc...
>>> Regards, Rob
>>>        Message was sent through the cbm-hackers mailing list
>>         Message was sent through the cbm-hackers mailing list
>       Message was sent through the cbm-hackers mailing list

       Message was sent through the cbm-hackers mailing list
Received on 2017-02-13 22:00:02

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