Re: Flaky ZipGS - need help!

[mdm@netcom.com (Mark Miller)]

In article <244j5m$ss1@reeve.research.aa.wl.com> schultp@aa.wl.com (Paul Schultz) writes:
>In the past few months I have upgraded my ZipGS. I bought the
>new 14 MHz 65816, new 35ns wide SRAM, and soldered in a new socket
>for inserting new oscillators. However, since upgrading to 
>11.5 MHz, 64K cache, (I was unable to get it to run at all at a
>faster speed -- i.e., 12 or 12.5 MHz) the computer will operate
>fine for anywhere from 1 to 3 hours but then it will suddenly
>freeze or lock up! I installed an internal fan and am running it
>with the top off but this doesn't seem to alleviate the problem.
>I only have a memory card and a SCSI card installed besides the
>accelerator (4MB GS Juice Plus and an old rev C Apple SCSI). I
>have the Zip INIT settings at the "defaults". Slowing the slots
>down has no affect either.

The Zip by design is not a heat sensitive device.

>I am wondering if I have done something wrong during the upgrade
>or whether I just have a flakey card/computer/whatever set-up.
>All chips and oscillators are oriented correctly and as far as I can
>tell they seem to be firmly seated.

It seems that the Zip has a bottleneck of about 12.5 MHz, unless you
make some more hardware modifications.  There was some discussion
earlier about how to obtain 16MHz with the Zip, however, most of
the details were left out.

Each new 14MHz 65816 is different.  You need to look at the schmoo
plot which came with your '816.  It will indicate the frequency at
which it can operate with respect to different voltage levels.  By
default you should look at the 5V rating.  The number at the bottom
of the schmoo plot is the period...to get frequency, take the inverse
of that number.

>I've actually been living with this problem for a couple of months
>since I finish up my "sessions" with the computer before it locks
>up. Oh, another piece of info: Its been a while but I remember that
>the same thing happened at 10 and 10.5 MHz.

If you are saying that you are unable to reliably run at 10 or 10.5
MHz even _after_ upgrading your Zip, then you may have an extremely
low performance 65816.  I was told by WDC that the average 14MHz
is rated at about 12MHz.

My Zip will do 12MHz, but not 12.5MHz.  I've been thinking about
upgrading to 16MHz, but I am not too certain on how to do it yet.

I, too, have the 35ns wide SRAMs for a 64k cache.  It seems that
we have identical Zips, however I have not had any troubles at
12MHz.

>Does this sound like anything that can be corrected?
>Any ideas?

Try operating at lower frequencies and gradually increase it (.5Mhz).
A good test is to run BackGround Sound while viewing a 3200 color
picture.  This test consumes a lot of CPU time.

-- 
`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`,`
`,`,`Mark Miller`,`,`,`,`,`,`,`,`,`,`,You gotta put down the ducky`,`,`,`,`
`,`,`mdm@netcom.com,`,`,`,`,`,`,`,`,`,if you wanna play the saxophone!`,`,`
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