Date   : Sat, 11 Nov 2006 13:07:55 +0000
From   : pete@... (Pete Turnbull)
Subject: DFS on 3.5inch - Is this supposed to work?

Jason Watton wrote:

> Okay, **how about a response** from those who say "Most PCs do not do FM 
> encoding"?
> 
> My plea: Back it up. What software are you using? Are you using the BIOS?

OK, here's my 5p worth.  I have three PCs which I have tried to run 
Anadisk and 22DISK on -- these are, respectively, disk analyser software 
and software to read/write CP/M disks, and AFAIK neither uses the BIOS. 
   They all work (more or less) for a variety of MFM formats but not for 
FM.  Two of the PCs are Intel Pentium motherboards, one is an Asus. 
Xenocopy is another program which doesn't work for FM on most PCs, but 
I've not used it on these machines, though I know the author.

I have one old 486 which hasn't been used in ages, but which used to 
work last time I used it.  I haven't tried either of my laptops, as one 
has no floppy at all, and my only use for the software would be with a 
5.25" drive.

You might like to look at archives of comp.os.cpm and similar places, 
including the CP/M FAQ and the Classiccmp mailing list archives.  Over 
the last few years there has been a lot of discussion about what 
controllers would/not handle FM reliably, and why (some cards can be 
modified, some can't, some controllers just work) and at least one 
person has made a careful study.  Many other contributors to the 
discussions have a great deal of experience in archival and 
retrocomputing.  The concensus a while ago was that most PCs won't do 
it; however since there has been a trend towards integration, you might 
be more likely to find motherboards with the right circuitry integrated 
in the FDC-and-kitchen-sink controller than in the past.  So, in some 
sense things might have been getting better.  Sadly, though, the trend 
is towards omitting the FDC these days, and even on PCs that still have 
the interface, it's often crippled by not having all the signal lines 
brought out (so only one drive select is connected, for example).


-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York