Re: 8250 and C64 disks

From: Nicolas Welte (
Date: 2006-03-28 07:22:15

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 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.

Of course, you had to decrease the bit clock as well to read the format 
with less sectors per track.

What I think would be possible: modify my program to support a 4040 drive.


       Message was sent through the cbm-hackers mailing list

Archive generated by hypermail pre-2.1.8.