flash (or ide) storage for unibus 11?

Fred Cisin cisin at xenosoft.com
Sun Nov 29 00:23:22 CST 2015

>> WD style: no problem with index pulse timing relative to data NEC765
>> style: index pulse is necessary during LLF, but may need to be
>> blocked during read/write, although a few of the newest drives may
>> not be happy without index.

On Sat, 28 Nov 2015, Chuck Guzis wrote:
> 765/8272 are particularly bad in this respect (they're blind for a full 
> millisecond or so) in contrast with 765A/8272A, which chopped the blind spot 
> by half.
> In the 8272 days, I added a one-shot to delay the blind spot by a varying 
> amount, which solved the problem neatly, while still allowing the index to 
> pass through.
> The index is also needed for WD17/27 family controllers also for LLF. Ya 
> gotta start (and end) somewhere.

Need index for LLF, but not necessarily for read/write, albeit with a few 

> If you simply block index with the 765 type FDC, you'll never get a "sector 
> not found" error--if you have a deadman timer, it'll expire.

Exactly.  It will time out, and get a time-out error instead of the 
requested sector not found.

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