Re: Another Zip story, episode 2...

[toddpw@lust.ugcs.caltech.edu (Todd P. Whitesel)]

o9938156@wsuaix.csc.wsu.edu (mark lyon) writes:

>- Putting capacitors across the power pins (I just piggybacked
>the small SMD capacitors that are already there) had no noticable
>effect (@ 8MHz).  I tried up to 120uF electrolytics, so size wa
> not the problem.  I also put .1uF caps across the 74ACxx chips.

Huge electrolytics are useless for what Jawaid was talking about.
Try .1uF/.01uF/.001uF caps on the SRAMs and see if that helps.

>Conclusion:  It was the increased capacitance caused by the
>shield that helped.  With the caps, the foil was farther away
>from the traces than without, so the capacitance was less.

And the shield's capacitance is very small; small caps are what you want
for noise. Large caps are good for preventing major power spikes, but
the Zip board (and any good Apple card) already has some.

>will give up and order some low power SRAM's, but even
>with low power rams, this may help to run a little faster.

I think the low power SRAMs will do way more to help than the metal
shield. But then, I've never had to resort to such B.S. to get my Zip
running at 10.5 w/ 64K. Let us know how it goes...

Todd Whitesel
toddpw @ ugcs.caltech.edu