grinding down chips was Re: QX10 graphics board

[Chris M]

so by your reckoning not all of the asics are readily
reproduceable. What about the gate array on the
graphics board (lets pretend there wasnt a primitive
ttl prototype to guide)? What about the 7220 itself?
Now something like that is bound to have loads of
docs.
--- cctech-bounces at classiccmp.org
<ard at p850ug1.demon.co.uk> wrote:
> > 
> > On 1/27/2006 at 11:33 AM Joe R. wrote:
> > 
> > >   Photograph it yes but a schematic is MUCH more
involved since all dies
> > >have multiple layers. It's sort of like trying to
make a schematic of a
> > >multilayer circuit board when all you can see is
the top layer.
> > 
> > Ditto that--and recall that we're talking here
about an old graphics
> > controller; no crypto and (relatively) very old
technology.  I'd rather
> 
> If we're talking about the Epson QX10, then there's
no problem at all.
> 
> The later version of the board (which is what's in
both my machines) 
> contaisn a 7220 (data sheet available), 16 RAMs, a
bit of TTL and an 
> Epson gate array. But the technical manual shows
schematics for that _and 
> for an earlier version_. That doesn't have the gate
array, it has more 
> TTL and a character generator EPROM.
> 
> There must be some differences between the 'extra'
TTL and the gate array 
> (IIRC there's a latch on a bus in one version that's
not in the other), 
> but they are sufficiently similar that you could
recreate a replacement 
> for the gate array based on the schematics in the
manual. The only thing 
> you wouldn't have is the exact font of the character
generator, but I am 
> sure you could create something that was readable.
> 
> A bigger problem in maintaing the QX10 are the 2
hybrids in the SMPSU 
> (but IIRC part-scheamtics without component values
are in the manual) and 
> the 2 ASCIS on the floopy drive. And you'd have
probllems swapping out 
> the complete drive as this is a 1/3rd height unit
(not to mention the 
> fact that you'd want to keep the original one since
it's an interesting 
> voice-coil unit).
> 
> -tony
> 


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