12 Oct
2011
12 Oct
'11
12:47 p.m.
Tony Duell wrote:
You have me wondering now! I thought I remembered a Whitechapel ("MG-1
type", i.e. not Hitech-era) machine with SCSI, but I'm not so sure *what*
exactly.
I've got board photos of a later CG-200 system and that appears to be an
on-board STxxx interface - and indeed I know that a couple of Bletchley's
MG-1 machines had STxxx drives and (once you got me thinking about it) I
don't recall a SCSI-STxxx bridge board being present, suggesting that they
too had integral STxxx.
Going against that though, the wikipedia page (yeah, I know! :-) for the
MG-1 mentions SCSI as being the interface, and there's also this MG-1 sales
flyer:
http://www.chilton-computing.org.uk/inf/pngs/mg-1-4.png
(be warned, it's a 1600x2300 image, so I'm not sure how easily you can view
it!)
That looks like a 50-pin header right around where the STxxx interface is
on the CG-200. Sadly the text just mentions integral Winchester disks and a
sophisticated disk controller, without saying what the actual interface is.
Unfortunately I've got photos of the outside of some of BP's MG-1 machines,
but not the internals, so I can't compare the sales flyer's PCB photo
against another genuine MG-1 (I can't find any others online). But it
almost seems like there might have been two completely different MG-1
main-boards around, one with SCSI and one with STxxx - if true though
that's quite a major change, and I'm surprised that it didn't warrant a
completely different model number.
cheers
Jules
Thinking about
it, Whitechapel's MG-1 had SCSI on the main PCB as standard
equipment, and that was in 1984, so a couple of years before the Mac Plus.
Does it? I've jeust been through the schematics and I can't find any SCSI
inerface. The hard disk interface is essentially ST412, but there's a
connector allowing acces to the HDC chip pins which was going to be used
for an SMD interface. Problem was, the DMA controller couldn;'t handle
SMD data rates... 