Re: HEeeeeeelp...

[David.Empson@bbs.actrix.gen.nz]

In article <djshaw01.728057418@starbase.spd.louisville.edu> djshaw01@romulus.spd.louisville.edu (Daniel Shaw) writes:
> also....what type of ram is the cache on the ZIPGSX?..I know the model...but
> I don't know the type...

Well, it is all 32k x 8 bit CMOS static RAM.  There are various
manufacturers, each of which has their own part code.  The part code
usually involves the number '256'.  '62256' and '43256' are a couple
that I encounter frequently at work.  If you have an 8k or 16k ZIP, it
uses 8k x 8 bit CMOS static RAM (6264 is the most common number).

The other factor is that the cache RAM has rather short access times.
My 8 MHz ZIP has 45 ns cache RAM, but a friend's 9 MHz one has 70 ns
RAM.  Determining how fast the RAM needs to be is somewhat of a black
art.  An approximation is to take the reciprocal of the clock
frequency, and halve that, then make it a bit shorter.

e.g.	 8 MHz -> 62.5 ns or faster (60 ns should be OK)
	 9 MHz -> 55.5 ns or faster (45 ns should be OK)
	10 MHz -> 50.0 ns or faster (35 ns should be OK)

The 'safety margin' needs to be greater at high frequencies.  For
example, at 14 MHz, the cache RAM access time needs to be 12 ns or better.

> 	what is the discusion about PAL's about? 

PAL stands for 'programmed array logic'.  It is a custom chip used on
the TransWarp GS to handle most of the logic functions.  The original
one isn't fast enough to handle very high clock speeds, so it needs to
be replaced with a faster PAL.  The 'program' in the PAL is not known
to anyone except Applied Engineering, so only they can supply one.
They are no longer supplying fast PALs (or so I've read).

> and lastly...on this new 65c816E or whatever...can it be placed on a zip.no hitches attached?????and how...

The new 65816 can be placed in a ZIP, but you will need to change the
crystal and cache RAM to appropriate values to make it go fast enough.

The ZIP's ASIC (Application Specific Integrated Circuit) has a design
flaw that prevents it running faster than 12 MHz without modifying the
board, so this is the practical speed limit of the ZIP for now.

To get the ZIP running at 12 MHz, you need the new 65816, a 48 MHz
crystal, and probably 20 ns cache RAMs (25 ns may be OK).
-- 
David Empson

Internet: David.Empson@bbs.actrix.gen.nz    EMPSON_D@kosmos.wcc.govt.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand