flash (or ide) storage for unibus 11?

Chuck Guzis cclist at sydex.com
Sat Nov 28 23:23:14 CST 2015

On 11/28/2015 06:57 PM, Fred Cisin wrote:

> 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.

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.

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.


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