Subject: Re: More ZipGS Q's: The RAM
Newsgroups: comp.sys.apple2
From: dempson@actrix.gen.nz (David Empson)
Date: Sat, 13 Feb 1999 03:24:48 +1300
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Martin Gruen <mgruen@shell.fastlane.net> wrote:

> 1)  I called AMT international today and asked for a price on the 32 kb x
> 8 sram at 15ns.  I was asked which kind (okay the next bit is vague I
> didn't understand much with the guy's accent).  The dip at 3.3v or the 15
> dip he said the difference is the length of the pins.  Anyone understand
> this and can clue me in?

I can tell you that you need 5V static RAM, not 3.3V.  I'm not sure what
this "15 dip" is supposed to mean, unless it is a way of referring to
the width of the chip.

The RAM chips used on the ZIP are "standard" or "wide" DIP, which is
about 3/10 of an inch wide (300 thou, in electronic layout terminology).

You can also get some chips in a "narrow" or "skinny" DIP package, which
is half the width but has the same pin spacing (and length).  This is
15/100 of an inch wide (150 thou).

Static RAM faster than about 45 ns is hard to get in wide DIP packaging.

The board actually has an option for installing narrow DIP RAMs, but you
would have to desolder the existing sockets and install new narrow ones,
or possibly cut away the current sockets and solder in half a socket to
get the extra row of pins available.

> 2)  I know there is a difference between what the Ram does on the card,
> but am I correct that all four sockets use the same kind of RAM?  At
> present I have two different chips on mine.
> which brings me to...

Each pair must be the same size (8K or 32K), and ideally all four chips
should be the same brand and speed.  In theory, the data RAM doesn't
need to be as fast as the tag RAM, but I'd be inclined to keep them all
the same.

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand