Re: ZipGS on eBay

[aiiadict@gmail.com]

I wrote:
> I don't know where you guys get your information..
>


Here's where I got my information:

#1)4 TWGS boards upgraded by myself since 1998, by
doing the following:
---install WDC 14Mhz 65816 CPU
---install 50Mhz oscillator (50/4 = 12.5)
---install new cpu cable
---if IIgs is full of cards, get heavy duty power supply


#2) I didn't just start hacking and hoping...  I read this
group and other Apple II users were having success,
so I decided to try it:

From: superti...@aol.com (Supertimer)
Subject: Re: WOLF3D fot A2 GS
Date: 1998/08/18
Message-ID: <1998081803060500.XAA29660@ladder01.news.aol.com>#1/1
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>Nope.  You need to cut the trace when upgrading to a larger
>cache, but you DON'T need to cut the trace when upgrading
>CPU speed.  Also, the SRAMs supplied on the stock daughterboard
>are quite usable at speeds of up to 12.5Mhz.
>That means to push a TWGS to 12.5Mhz, you just swap the CPU
>and oscillator.  I've read of some units that go faster.

>- Original firmware does not support beyond 6.25 MHz

The great majority of TWGS came with 7Mhz CPUs and the
ROM v1.5 firmware that supports speeds up to 15Mhz.



AND:


From: superti...@aol.com (Supertimer)
Subject: Re: ZipGS or TWGS, which is better?
Date: 1999/07/20
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The main disadvantage of the Zip GS is that on most cards, you
need to change the cache RAM chips in order to go into speeds of
12.5Mhz or greater.  The regular TWGS comes with cache RAM
chips fast enough to go 12.5Mhz (as mine does).  But the speed
of the cache RAM chips provided on the Zip GS from the factory
will be too slow in most cases to get 12.5Mhz or greater.




AND:


From: mys...@direct.ca (Herbert Fung)
Subject: Re: New chip in TWGS
Date: 1999/09/12
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The CPU itself can probably be pushed to 20MHz but according to others
you'll probably need faster than 15ns SRAMs. The fastest reliable speed

for stock TWGS's I think was 12.5MHz.



AND:


From: Bryan Villados <news...@macgeek.org>
Subject: Re: New chip in TWGS
Date: 1999/09/13
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If you only change the CPU and left the oscillator at
28Mhz, you are in effect underclocking the fast CPU
at 7Mhz.


What you have to do is replace the current oscillator,
28Mhz (which means 7Mhz CPU speed) with a faster
one.  32Mhz oscillator means 8Mhz CPU.  36Mhz=4Mhz.


I suggest a 40Mhz and a 50Mhz one for testing 10Mhz
and 12.5Mhz CPU speeds and perhaps a few faster
ones to see how fast your TWGS can go.




AND:


From: superti...@aol.com (Supertimer)
Subject: Re: New chip in TWGS (sources for oscillators)
Date: 1999/10/25
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corne...@san.rr.com (L. Cornelio) wrote:

>superti...@aol.com (Supertimer) wrote:
>
>>If not, I suggest getting the 50Mhz and 40Mhz units.
>>12.5Mhz TWGS (50Mhz oscillator) almost always
>>works, but with a 40Mhz unit, you can fall back on
>>10Mhz operation if necessary.
>
>FYI, my ZipGSX works fine w/ a 40 mhz & no chip swap.
>Does that maybe imply that w/ a chip sway 50 or even 60 will work?

Very likely yes.  Especially the 50.  What was the Zip
clocked at before?  If you have the 8Mhz processor of
the Sanyo design, you have a very overclockable chip.
It does not hurt to give it a try.

>I was wondering which cards were considered more
>"easily upgradeable" the TWGS or the Zip.....

It depends.  TWGS is simpler to upgrade all other
things considered.  It has cache RAM fast enough
so that to upgrade it usually involves changing only
the oscillator and the CPU.  For minor speed
upgrades, sometimes only the oscillator needs to
be replaced.

But the TWGS is older.  It came with either 6Mhz
or 7Mhz CPUs of the older design.  The 6Mhz
version was not very overclockable.  Thus, for
major speed upgrades you need a new CPU for
the TWGS.

The Zip GS started with CPU chips of the type used
in the TWGS, but the Zip GS survived long enough
that they started using the Sanyo versions of the
chips.  These came in either 8Mhz or 14Mhz
versions.  These were VERY overclockable.  Some
people have pushed the 8Mhz chip to 15Mhz, for
example.  So if you have the "good" 8Mhz chip,
you can often avoid a new CPU and thus save a
step compared to the TWGS.

BUT if your Zip GS started out with the older
7Mhz CPU of the non-Sanyo design, it is usually
harder to upgrade than a TWGS.  That's because
7Mhz Zips came with slow cache RAM chips.
So on older 7Mhz units, the cache RAM chips
often needed to be replaced.  This is difficult
because fast cache chips are now available only
in the 300 mil packages.  Zip GS uses 600 mil
ones.  Thus adapter sockets must be used.
These are rather expensive ($7 each).  It is
either that or solder a new row of socket pins
for each cache RAM chip to plug into.