Disk imaging with IMD - question

Fred Cisin cisin at xenosoft.com
Wed Aug 9 14:41:14 CDT 2017

> If you can use IMD to format both FM and MFM at 500Kbps on your 242--and
> "Analyze" reads the format okay, your SCP disks aren't probably standard
> IBM 3740 or System/3 type diskettes. They could be in a proprietary
> recording format, such as Intel MMFM or Futuredata GCR.

On Wed, 9 Aug 2017, Richard Cini via cctalk wrote:
> Thanks Chuck. The Gazelle uses the Tarbell DD controller which uses a 
> 1793 which I believe is 3742 and s/34 compatible.

The [WD] 1793 is normally used for "standard" FM and MFM formats
(What I call "IBM/WD Stle formats", and that I think Chuck called "IMD 

BUT, it could be used for some OTHER formats that the NEC-style FDC can't 
handle, since unlike the NEC-style chips, the WD-style chips have the 
capability of a "track write"/"track read", with seriously different 
sector header structures.
Not enough diffeernt to do GCR, but maybe enough to do Amiga?

The NEC can do a multi-sector read/write, but that isn't the same, and it 
can't do ANYTHING other than "IBM/WD-style" formats.

PC normally uses an NEC-style controller, and that is the only type that 
the BIOS supports.
At one point, there was an after-market WD-style controller with device 
driver support, but the added capabilities weren't enough to make it a 
market success.
If anybody has one, it has the capability of reading a number of disks 
that the NEC can't.

My naming convention is flawed.  I think that at one point Western Digital 
made an "NEC compatible" controller, that isn't what I call "wd-style"

Grumpy Ol' Fred     		cisin at xenosoft.com

More information about the cctech mailing list