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Re: ZipGSx Upgrade Questions (I've read the FAQ's)
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In article <3A0DDF69.9C697C9D@swbell.net>,
Rubywand <rubywand@swbell.net> wrote:
>> ** Replacing the 74F00 chip with the 74HC00 one **
>
> Where did you find this in the FAQs?
I can't speak for the original poster, but I recall reading this in one of
the accelerator-upgrade FAQs.
> Do not know why anyone would replace a 74F00 with a 74HC00 on an
>accelerator board. The 74F00 is a much faster gate than the 74HC00. You would
>think that when speeding up a board you would, if anything, want to move to
>faster gates. Suggest you leave your 74F00 where it is until whoever made the
>recommendation explains it.
This could explain why my computer has been a bit unstable since I modded my
ZipGS (14-MHz processor underclocked @ 12.5 MHz (who sells 56-MHz
oscillators?) increased from 7 MHz, 64K cache increased from 16K). Even
sticking an extra power connector on (a connector like you'd find on a hard
drive, drawing from a 250W power supply I hacked into the computer) hasn't
provided a substantial improvement. Adding a few decoupling capacitors in
selected locations (.1 uF across +5 and GND on each cache chip and 10-100 uF
electrolytics in some places provided for them along the bottom) didn't have
much of an effect. Mainly, the system crashes while in GS/OS...ProDOS 8
seems more stable. The computer also has a rev. C RamFAST, a SoundMeister,
and a RAM-GS 4-meg memory expansion installed.
Time to dig up the 74F00 I pulled out and see if putting it back in will
make an improvement...
(I thought it was in the comp.sys.apple2 FAQ, but it wasn't. It also wasn't
in the HyperCard stack mentioned in the section on accelerators. Digging
into some archived mail, I received some advice there that the 74F00 ought
to be replaced with a 74HCT00 (which is what's on mine). IIRC, the only
difference between HC and HCT parts is that HCT parts can be mixed with TTL
(the "T" is for "TTL-compatible"). Are HC parts that much slower than F
parts? I could look it up, but I'm a bit lazy right now. :-) )
_/_
/ v \
(IIGS( Scott Alfter (remove Voyager's hull number for email address)
\_^_/ http://salfter.dyndns.org
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