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From: knudsen@ihnss.UUCP
Newsgroups: net.micro
Subject: DOUBLE-Speed POKE for Color Computer
Message-ID: <1576@ihnss.UUCP>
Date: Tue, 28-Jun-83 20:27:43 EDT
Article-I.D.: ihnss.1576
Posted: Tue Jun 28 20:27:43 1983
Date-Received: Wed, 29-Jun-83 09:43:32 EDT
Lines: 18

Most Coco hackers know that the system's speed can be upped by about
40% by doing POKE &HFFD7,0 (or storing anything into HEX FFD7).
However, the various manuals warn against poking to FFD9 also,
which fully doubles the speed.  In particular, transparent RAM
refresh goes away, along with the video display.
However, some local guy (Ed M) tried it anyway, and it works!
In fact, it doubles speed of all-RAM programs (i.e., machine code);
the old 40% job did nothing for these.  Apparantly the SAM chip steals
the bus once in a while for refreshes so the RAMs stay up.
Yes, the screen becomes a blizzard, but anything you've output while
in double-speed mode will be there upon "re-entry".
NOTE: You must work your way up and back down by going thru the
FFD7 poke first (do it last on the way down, I mean).  Motorola
does point this out in the 6883 (SAM) specs.
So, let's hear some serious music & speech synthesis out there!
	mike k
(PS: no insult intended to the great speech & music work already done
by Coconuts!)