Xref: utzoo comp.os.os9:379 comp.sys.m6809:1005
Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!dneast.dec.com!burke_vern
From: burke_vern@dneast.dec.com (Mah biscuits 're burnin'!-Yosemite Sam,_Roger Rabbit_)
Newsgroups: comp.os.os9,comp.sys.m6809
Subject: coco III mod
Message-ID: <8902131928.AA11974@decwrl.dec.com>
Date: 13 Feb 89 19:28:51 GMT
Organization: Digital Equipment Corporation
Lines: 31




	Here's some more info on the coco III mod.I built a satellite
	board so I could easily convert the coco III back to the
	original configuration.I used a 16 pin dip to dip ribbon
	cable from RS to connect the board to the original 74ls138
	socket on the coco.All the pins on the cable run to the
	same pins on the 74ls138 except pin 4.Run a wire from pin 3
	of the 74ls138 to pin 3 of a 7402.Run a wire from pin 1 of
	the 7402 back to pin 4 of the 74ls138.Connect pin 2 of the
	7402 to E clock(I used pin 34 of the 6809 for this).Tie
	pin 14 of the 7402 to +5v and pin 7 to ground.
	The NOR gate is absolutly necessary for this to work.The
	system will not run at all using just e clock as the enable.
	I'm not sure wether this will work with the older version of
	the GIME.The original GIME carries a part # of TCC1014.The
	new one has an "A" suffix.
	"Sparklies" are linear flashes of light that appear on the 
	monitor screen especially while floppy access is going on under
	OS9.The "A" GIME was supposed to cure this,but it didn't make
	much difference (in my case at least).I've been running my system
	with this for 3 weeks now,and I havn't seen any problems.I'm 
	running a coco III,old multipak(upgraded),dual mode controller,
	original coco-xt(without the gating modification),2 5 1/4"
	floppys,and a 10meg hard disk.Prior to the mod,I have was having
	a lot of problem doing floppy formats after booting from the hard
	disk,esp when using an interleave of 1.Sometimes it would work,
	sometimes I'd get an error 253.I havn't seen any reliability
	problems at all since I made the modification.
							Vern