[Coco] Coco 4

[Gene Heskett]

On Tuesday 06 January 2004 15:18, jadonaldson at charter.net wrote:
>  If you look at the Burk & Burk interface, it interfaced
>to 8 bit ISA Hard Drive interfaces.
>
>John Donaldson

If you reverse engineer that one, use a later version as the sample.  
My very early one must have had a timing problem or something with 
resulted in an access of the fat returning a sector that was zeroed 
out.  As you can imagine, thats what led to my relative expertise 
with the os9 file system, I was always re-constructing something from 
scratch after a disk write.

I now have a several years later, gold colored version that has been 
absolutely, totally bulletproof.  At one point in my testing of that 
one, I had a cron job that formatted a 10 meg tandon and dircopied 
what was on it to a 20 meg st-225 on even nights, and reversed it on 
odd nights, each time running a dcheck against the new copy.  I let 
it run for a couple of weeks, until the night crew started 
complaining about the squeaky ground spring on the end of the tandons 
drive spindle.

Toward the end, that system only existed to support the "edisk" I'd 
written for the Grass Valley 300 switcher we had, so it didn't get 
much use.  We had far more trouble with aging chips in the switcher 
than with that coco2.  That thing was designed at about the time the 
semi folks were first learning about the purple plague that attacks 
early nmos and pmos stuff.  Specialty chips, apparently made in small 
qty's just for Grass, were dying like flies.  So were Grasses own 
inhouse built ceramic hybrids, many of which could be simplified to 
an op-amp that National Semi would have classified as "Damn fast" 
with gain/bandwidth products in excess of a gigahertz, and which when 
the legs were steered to the right holes in the pcb, easily 
outperformed the hundred bucks plus a copy Grass devices with a 
sample that could be had from Newark et all for $1.70 in 25'sies...

I guess it could be for sale, somebody should make me an offer, 
although I think the tandon needs a bump to start it these days.  The 
drives are mounted in an old pc power supply shelf and running from 
that power supply IIRC.  That would be the later B&B controller, all 
the cables I was using, the two drives and psu shelf they are sitting 
in.  No fancy case for the drives in other words.

-- 
Cheers, Gene
AMD K6-III at 500mhz 320M
Athlon1600XP at 1400mhz  512M
99.22% setiathome rank, not too shabby for a WV hillbilly
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Copyright 2003 by Maurice Eugene Heskett, all rights reserved.