[sebhc] 444-66

Peter peter59 at sbcglobal.net
Sat Jun 19 18:11:26 CDT 2004

The trick with speeds over 4MHz was to implement speed switching in the OS.
When the computer needs to access certain hardware, I would have it switch
to 2MHz operation till the I/O was completed. This was not necessary for a
4MHz mod. Although I have not done it successfully myself, I have had
reports of some users running at 8MHz. I don't remember any more who did
this - it was quite a while ago.

As for the 444-66 source, I do not have it. The units I have were simply
copies from the original but burned to higher speed PALs. I do not have
equipment to do this - I contracted another person for these parts. They
only cost a few dollars apiece. I totally forgot about them till just now. I
also found my stash of 74HCT00 ICs that were also a necessary part of the
speed upgrade process.

I just got back from moving my daughter into an apartment for the
university. As soon as I get organized a bit, I will try to post the
information for increasing the CPU speed - perhaps it might be easiest to
put it on my own website and I will give post the URL on this list. Any
comments on doing it that way?

peter59 at sbcglobal.net - http://www.geocities.com/anapro.geo/

> -----Original Message-----
> > While searching for a power cord, I "found" a package of 
> some 444-66 ICs
> > that I had made for my 6MHz H89 modification. These are 
> Cool!
> I'm running one of your 4 MHz mods in my main H89 right now. Out of
> curiousity, what else would be required to change it to 6 MHz?
> --
> --
> Lee A. Hart  814 8th Ave N  Sartell MN 56377  
> leeahart_at_earthlink.net

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