Re: FAQ-Zip GS upgrade: The 10MHz alternative

[wbaguhn@nyx10.cs.du.edu (Will Baguhn)]

In article <h339308@pro-palmtree.cts.com>,
Richard Der <rder@pro-palmtree.cts.com> wrote:
> 
>Note:  Even if you need a new cache and CPU in addition to a new
>       oscillator, you can still upgrade a 7/32 to a 10/64 and beyond
>       for around $40. If you are satisfied with 10MHz and are lucky
>       and don't need the new cache and CPU, then you'd get a 10/32
>       upgrade for the price of a $1.39 oscillator!
>-----------------------------------------------------------------------
> 
>Good luck.
> 
>(Note: The speed of these SRAMs will be sufficient to around 10MHz.
>       The advantage of these particular chips are that they are
>       available cheap and in the wide 600 mil package that the Zip
>       sockets require.
> 
>       For 15MHz operation, even faster SRAMs may be required.
>       Unfortunately, they are mostly available only in the skinny
>       300 mil packages.  To use them, half sockets must be soldered
>       into the Zip.  They are also more expensive.
> 
>       Also consider that the performance advantage going from 10MHz
>       to 15MHz is far less dramatic than from 7MHz to 10MHz.  Factor
>       in the risk of seriously damaging the Zip during soldering.
> 
> Conclusion: the 10MHz operation is safer, requires no permanent
>             modification of the Zip, and the chips of the right
>             size are available and costs a lot less.)
> 
>Please distribute this document freely.  Apple II Forever.
>
>
>-----
>The Palmtree BBS  310-453-8726 v.32
>Inet: rder@pro-palmtree.cts.com
>

The 10 MHz operation may be safer, but my 12/64s (waiting for a 56 MHz xtal)
will still beat it.  Yes, I had to modify the Zip with half-sockets,
but i'm running on 15ns cache chips now... with absolutely NO problems.

If you have a clue (i.e. can solder worth half a grain of salt),
I recommend going for a processor swap, new crystal, and a 64k split cache.
Maybe a 74HC00 if you start having problems, as the 74F00 can't keep up
past a certain point (I believe I heard 12.5 MHz as a magic number).

If you haven't a clue, just swap the processor and pop in a different
crystal, and MAYBE install a bigger cache if you can find the wide
(or narrow, whatever matches your sockets) cache chips.

(note: i've had people comment that my soldering looks almost as good
as machine soldering. I don't believe it, but i want you to understand
that you NEVER solder on an expensive, delicate board without knowing
pretty well what you're doing, and also knowing that you're risking
overheating the chips and frying the board, as well as static-shocking
the cache, processor, and possible the caching logic... i.e. you're
risking that you'll have to replace the whole board if you toast it.
That said, do it CAREFULLY.)

-- 
                                      --- Rev. SPQR (wbaguhn@nyx.net)