SASI device <-> PC ?

Tony Duell ard at p850ug1.demon.co.uk
Thu Jun 30 14:39:32 CDT 2005


> 
> 
> Has anyone here successfully interfaced a SASI device to a PC at the
> hardware level?
> 
> I've got a few classic systems which use SASI (or not-quite-SCSI)
> controllers to talk to SASI-ST506 bridge boards and from there to ST506
> type drives.

I was under the impression that SASI was sufficiently close to SCSI that 
a SCSI interface could talk to a SASI device given the right software. It 
would probably make things simpler if the SASI device and the controller 
were the only things on the bus.


> 
> As has been documented many times in the past here, an ST506 drive has a
> pretty tight relationship with its controller, and so hooking up the
> drive to a different controller (say MFM controller in a PC) causes all
> sorts of problems when it comes to backup.
> 
> Hence driving the SASI side of things (and preserving the drive/bridge
> board relationship) would seem like a sensible move when it came to
> backing up data. In theory data could then be restored to a replacement
> drive if/when the original dies via the same method.


Agreed.

> 
> Presumably inventing a simple SASI board to hang off a PC parallel port
> (say) is a lot easier than mucking around with the equivalent for floppy
> drives - or is the data rate still likely too low to cause timeout
> problems within the bridge board's firmware?

I am pretty sure you can drive it as slowly as you like. All the bridge 
boards I've seen have intenral buffer memory, certainly enough for one 
block. 


> 
> I've got several Acorn, Torch and RML machines which use bridge boards

FWIW the Torch XXX uses a SCSI interface chip on the mainboard, and I 
thought the drive bus was SCSI on that machine.

-tony




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