Re: Zip GSX Mod to 12.5Mhz (or better)

[Polymorph <polymorph69@hotmail.com>]

On Sep 24, 3:41 am, Steven Hirsch <snhir...@gmail.com> wrote:
> Polymorph wrote:
> > Hi All,
>
> > As promised in another thread, I have posted details of how I modded my
> > Zip GSX to run at 12.5Mhz. It includes the complete parts list, and
> > pictures of how to perform the modification to your board (if you are
> > game).
>
> > Check it out, and let me know what you think:
>
> >http://apple2.sytes.net/ZIP_GSX_Mod/index.html
>
> Very cool idea!  I was planning to remove the 0.6" DIP socket outright with a
> vacuum desoldering station.  Your approach is a _lot_ safer.
>
> I notice you didn't replace the two 74F parts.  When/why is this necessary?
>
> Steve

The original hypercard stack used 0.6" to 0.3" adapters to fit the
high speed SRAMs, but I thought that they were way over-priced and
also increased the width of the board to the point that the slot
adjacent to the Zip GSX would probably become useless due to
encroachment.

If you want to go much higher than 12.5Mhz it *may* be necessary to
replace the 74F parts. Some people have reported getting 15Mhz using
the 74F parts, whereas others have had to do the 74ACTQ replacement. I
wanted to keep my mod as simple as I could for now - I didn't want to
have to desolder anything from the board as I do not have good enough
tools at this stage (the traces are very small and numerous). I hope
to eventually try pushing the card to a higher speed, but I'm pretty
stoked with 12.5Mhz at this stage - it is quite noticably quicker than
8Mhz with 16K cache. I expect I could go a little higher than 12.5Mhz,
but I don't have any crystals between 50Mhz and 64Mhz to test with
yet.

cheers,
-p