Re: ZipGS/Ramfast problems finally solved!!!!

[dempson@actrix.gen.nz (David Empson)]

David de Sosa <dmds@msg.ti.com> wrote:

> [ZIP has 32K cache, but only works if set to use 8K.]
> 
> Now I'm curious as to why only the 8K setting works.  There are two 16K chips
> onboard so how is it possible that only 1/2 of one of the chips work?

A ZIP GS with 32K of cache has two 32K RAM chips.  One of them contains
cached data, and the other is "tag" information which the cache
controller uses to keep track of the source of the data.  If you look at
the board, you will see "TAG" and "DATA" written above the appropriate
chips (two of each if you have a fully populated card).

If you set the ZIP GS to use 8K of cache, then you are only using a
quarter of each of the two chips (the upper two address bits going to
each RAM chip are probably always zero, or at least are always the same
value).

> Would it be worth swapping the original chips out with faster ones?

Possibly.  The TAG RAM is more sensitive to speed than the data one, but
you might as well swap both of them.

You didn't mention the speed of the accelerator, so I don't know what
speed RAM you need.

> Or is there some component on the board which is the likely culprit that I
> could replace?

If there is a faulty component, it would be the large ASIC, which is not
replaceable, or something like a damaged track (not likely).

> Also, just how much speed am I losing with 8K instead of 32K on?

It depends on what the software is doing.  It means that you will be
running at the standard speed of the computer for a much higher
proportion of the time.

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