SCSI to MFM/RLL schematic

Chuck Guzis cclist at
Sun Nov 28 17:46:56 CST 2010

On 28 Nov 2010 at 22:50, Phill Harvey-Smith wrote:

> Hi,
> Does anyone happen to have the schematic of one of the SCSI->MFM/RLL
> boards ? I have the Adaptec ACB-4000 and Xebec S1410A board documents
> from bitsavers but thy only have the schematics for the computer end.
> All the talk  of interfacing to SCSI has got me wanting to have a go
> :) I'm just want to look and see how it was done in the olden
> days....failing that I guess I'm gonna have to start tracing
> tracks.....

I've got a couple of the OMTI 3127 RLL-to-SCSI converters.  They 
basically have the OMTI RLL hard disk controller, a Z8 MCU, some 
EPROM, RAM and an NCR-licensed SCSI bus interface chip.

Another example of SCSI-to-something else can be found in the various 
tape drive interfaces.  Cipher used an 80188 and an NCR SCSI 
interface for their M990 tape streamer (the drive controller itself 
is a Z8002 MPU).  

You can see a similar pattern in scanners and the like--an MPU, some 
ROM, some RAM and a bus interface chip.

If I were to make a SCSI hard disk substitute today, I'd probably use 
an ARM M3 with external RAM interface (for cache), some SRAM,  an 
SDHC for storage and whatever I could find for a bus interface IC.

On the other hand, SCSI-to-USB may be a more logical choice, given 
the wider range of USB devices available.


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