Re: 8250 and C64 disks

From: Claus Just Rasmussen (
Date: 2006-03-28 21:35:13

Hi Nicolas,

Nicolas Welte wrote:
> Claus Just Rasmussen wrote:
>> Hi all,
>> I have a SFD 1001 (~8250) connected to my PC using a NI IEEE card, 
>> and I've been reading some old disks with that setup (Thanks for the 
>> help Nicolas and  Ruud !! )
> Oh, it worked now!? What was the problem? 4040 disks?
A combination - some 4040 disks and also imgrd, I'm afraid. The 4040 
disks explains itself, the imgrd problem was/is that if I specify a 
filename in actual path, then it'll be overwritten by something <2KB. 
The solution was to specify c:\filename instead. The result is then a 
file in c:\ (which cannot be used) + a file in current dir named d82 (or 
d80) which contains the actual image. Perfect but not exactly what I 
expected in the first place :-)
>> A have a few disks, which cannot be read though. Probably in 4040 
>> (~C64) format.
>> As far as I know: The high-capacity drives isn't capable of reading 
>> the lower-capacity disks AFAIK. But on the other hand - with correct 
>> SW *and* tracks (luckily) positioned so that they overlap tracks on 
>> the 8250-format should make it possible to read them anyway ?!
> The tracks do not overlap, unfortunately. The 8250 uses 100tpi track 
> density, the 4040 uses 48tpi. Only if the 8250 had a 96tpi drive (like 
> the usual 80 track drives in PCs do) then there would be some chance 
> to make the 8250 read those disks.
OK. A shame :-(
> Of course, you had to decrease the bit clock as well to read the 
> format with less sectors per track.

I managed to get my hands on a 4040 so now I've got the HW in place to 
read the disks. Really nice.

Next question: Do a 4040-version of imgrd exist? If not - will I need to 
change more than the #sectors,tracks? (bitclock?)

> What I think would be possible: modify my program to support a 4040 
> drive.
> Nicolas
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Claus Just Rasmussen, BSc.EE.

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