[rescue] EIO card in HP 4M

[Mouse]

>> I'm more concerned about VSIMM failures.  [...]
> Given the amount of people recreating PCBs for old hardware
> (OpenTendo, SnarkBarker, replacement motherboards), I wonder what it
> would take to make replacement VSIMMS.

In a word, I would guess, documentation.

> I guess the first question would be what chips are on the VSIMM.
> Looking at photos online, it looks like there is a custom ASIC with
> LSI branding, so I guess it would probably be pretty complicated to
> figure out how to work around that.

Indeed.  Some of the cg14 is on the motherboard (notably, much of the
analog electronics involved), but certainly some of the intelligence is
on the VSIMM.  I'm not aware of any documentation on the interface.

> I wonder if that or the RAM chips die more frequently.

I don't think I've had either die yet, and in any case I would have
only anecdotal information.

> I also wonder if it would turn out to be feasible to upgrade 4MB
> VSIMMS to 8MB.

4M VSIMMs, at least the ones I have, do have unpopulated solder pads
apparently prepared for another set of RAM chips.  Running one of them
in a mode requiring 8M, such as 1920x1080 24bpp, works, if you don't
mind having most pixels aliased with other pixels - it looks to me like
what I'd expect to get if the top VRAM address bit were being ignored.

I don't, of course, know whether simply soldering in more chips would
be enough, or whether there's something else that would have to be done
to convert a 4M part into an 8M part.  I would _guess_ that it's a
matter of a jumper install or etch run cut or something equivalent;
these mostly predate the more extreme anti-aftermarket-mod measures.
Next time I have my machine with the 8M part open, I may compare it
with a 4M part and see if I can see any difference aside from half the
RAM chips.

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