Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10 5/26/83; site ihnss.UUCP
Path: utzoo!linus!decvax!harpo!eagle!mhuxi!houxm!ihnp4!ihnss!knudsen
From: knudsen@ihnss.UUCP
Newsgroups: net.micro.6809
Subject: Re: Disk & Fast Poke: FIXED...
Message-ID: <1714@ihnss.UUCP>
Date: Mon, 3-Oct-83 13:29:12 EDT
Article-I.D.: ihnss.1714
Posted: Mon Oct  3 13:29:12 1983
Date-Received: Tue, 4-Oct-83 01:04:19 EDT
Organization: BTL Naperville, Il.
Lines: 18

I checked my Technic Ref Manual for Coco and was amazed to find
that the CTS- (Cartridge Select) line is horrendously low-pass-filtered!
Not just a 470 ohm resistor in series, but a 220 pf cap shunt to ground
after that.  I think the numberss were R80 and C7x.  The Cap is right by
the connector; R80 is in the center of the board.
These parts caused the CTS- enable to look more like a sine wave than a digital
pulse!  After persuading these components to depart from my Coco's innards,
I now have a digital signal.  I guess home computers are like cars--
you gotta remove a few air-pollution government-pacifier parts to
get full performance.  (I noticed NO more interference on my TV set
afterwards.)

Can now run speed POKE &HFFD7,0 with disk in, but you can't really USE
the disk due to software timing loops (head seek goes ape).
Trick is to add code to slow down machine during I/O, run fast rest
of the time.
Also note that the ROM chips in utility cartridges like BASIC-AID and
SDS-80C are themselves too slow to run in fast mode.