18 Oct
2011
18 Oct
'11
4:51 p.m.
On 18 Oct 2011 at 16:16, Glen Slick wrote:
Is there any peculiar with the 128-byte / sector MFM
format? Or is it
more likely an edge case that probably should have worked in the
controller but wasn?t tested until too late? Or was support for that
format was intentionally dropped from the controller?
NEC never claimed that 128-byte MFM sectors would work. Their
datasheets don't list it--and anyone who's tried to read or write a
128-byte MFM sector using the 765 got some eye-opening results--the
first 80 (decimal) bytes would be transfered, but not the remainder.
Since the reference standard for MFM on 8" disks was IBM System/32
(53FD) used 256-byte sectors, it might be that NEC didn't think that
the 128-byte MFM type would ever be used.
In theory, it's possible write sectors smaller than 128 bytes, but
I've never run into a system that actually did that.
--Chuck