17 May
2007
17 May
'07
3:55 p.m.
On 16 May 2007 at 12:41, John S wrote:
Using D to read data, I could read track 0 OK, but
with higher tracks
(especially 10 or higher) then IMD gave errors like:
Read error <1> No Addr Mark 2
Read error <2> No Addr Mark 3
etc up to sector 10.
Then it doesn't sound like alignment or the usual suspects. It
sounds very much as if the diskette was formatted (past the first
cylinder) using a nonstandard DAM, which is supported by the WD 17xx
controllers, but not the NEC 765-type. The standard convention is to
use FB as a DAM or F8 as a DDAM. However, the WD chips can write DAM
values of F8, F9, FA, FB, FC and FD. Anything other than FB or F8
will cause the NEC-based chips to choke.
There's no easy workaround with PC hardware for this one. If a
customer needs data interchange on a PC, we'll suggest that he format
up a diskette on his PC using 22Disk, then copy the original to it
and use the result for his transfers. You could use a Catweasel or
any other edge-sampling type of FDC. Here in the shop, we have an
ISA PC board set up with a WD controller.
While this situation doesn't occur frequently, it does happen.
Cheers,
Chuck