8" drive variations

[Chuck Guzis]

On 13 Mar 2007 at 13:49, Jules Richardson wrote:

> Generally-speaking I suppose I can just mess around with jumpers in the short 
> term if there's anything I need to change between reads for different formats; 
> maybe in the longer term there's a project to add parallel port control to 
> ImageDisk and twiddle certain bits under software control, which can then be 
> used to do various things :-)

Typically, one can leave the jumpers set one way for any given 
installation; the only time you'll ever need to change them is for 
hard- and soft-sectored operation--and then, your installation is 
likely to change also.

Yes, you can disable the onboard FM separator--it's usually not the 
best implementation anyway--just a couple of one-shots.

> Those are less of an issue I suppose; it's just cabling and mounting and power 
> routing! I'm more worried about signal incompatibilities, I suppose.

If you want to be safe, stay away from the very early models.  Some 
early drives require 3-phase stepper signals, for example.  Some, 
such as PerSci have a buffered seek and so return SEEK COMPLETE\; 
some, such as the CDC BR803's don't have a READY\ line.  Innovex also 
has a MEDIA UNSAFE\  line.  Some, such as the aforementioned-CDC, 
don't use a DIRECTION\+STEP\ protocol, but rather separate STEP IN\ 
and STEP OUT\ lines.

As I mentioned, early Japanese drives (NEC, Mitsubishi) can be real 
connundrums to puzzle out.

Tony mentioned the bit about TG43\.  If you're just reading, this 
doesn't matter--and some drives take care of things internally.

Stick with a late-model Shugart 850-compatible drive and you'll be 
okay.

Cheers,
Chuck