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Re: Zip GSX CPU Cable Plug question, and others.

mmmann wrote:

Since I just went through the upgrade I'll post what I know.
I have 64K cache but no better than 8Mhz which is an issue that is still unresolved. See "Failure speeding up ZipGS - advice wanted" for more information. I believe it boils down to either having the wrong oscillator or needing a better power supply. 

Here are the parts.

JDR Microdevices (http://www.jdr.com):

(*) Various oscillators (ITEM NO OSC48.0, OSC40.0) ~$4.00.
(2) ITEM NO HM62256LP-70, SRAM, 32KX8 (LST62832I-70LL) $6.38.
(2) ITEM NO HM62832-12, SRAM 32KX8 (7C199-12/61C256) $11.98.
(2) ITEM NO HM62832-20, SRAM 32KX8 (7C256/68257) 28DIP $8.98.
I purchased two skinny 12ns static RAMs, two skinny 20ns static RAMs and two of the 70ns RAMs which are the wide parts interestingly enough. The FAQs on speeding up say that the cache RAM must be slower than the tag RAM. So I figured on trying 12ns in tag and 20ns in data. As a fall back position I could go 12 or 20 in tag and 70ns in data. That's what I'm running right now (20 and 70) since I found instability with 12 and 20 even at 8Mhz.
To get the skinny static RAMs to work you need to purchase adapters from Digi-Key (http://www.digikey.com/): 

(4) ITEM NO A502-ND, 28 PIN ADAPT SOCKET .300 TO.600.

I don't have the receipt so double check the item number, etc.
Also, I purchased the 14Mhz CPU but it's not doing me any good since I've failed, so far, to accelerate the board. When I have some time I'll circle around again and investigate more, but I find that 8Mhz and 64K RAM is fast enough. 

Did you ever verify that your non-8MHz oscillators are working?

You should try a 28MHz or another 32MHz oscillator, just to be sure that
your board's non-operation with other than the original oscillator has
anything to do with the board itself.

-michael
"Warren Ernst" <wernst@gmail.com> wrote in message 1139027339.349606.56400@g44g2000cwa.googlegroups.com">news:1139027339.349606.56400@g44g2000cwa.googlegroups.com... 


All,

So my ebay-ed Zip GSX arrived. It seems OK, but I have three questions:

1. The CPU plug (at the end of the ribbon cable, that plugs into the
CPU socket) is missing Pin # 21. I am assuming this is broken, and that
I need to fabricate a new cable. True?

2. Just to the left of the ribbon cable connector on the board, labled
T6, I have a small length of bare wire connecting the two solder pads.
Is this normal?

3. Both of the Tag and Data RAM sockets are filled with 8k SRAM chips.
Whats the best source for the 64k SRAM chips I've been reading about in
10-year old posts?

Thanks for the info.

-Warr