[Coco] SALT

[Gene Heskett]

On Sunday 07 April 2019 09:20:15 M. David Johnson wrote:

> On my 64K CoCo2, the SALT Chip is marked both SC77527P and 8345, and
> is at U1 on the motherboard, just to the left of the row of DRAM chips
> as you're sitting in front of the keyboard.
>
> --
> M. David Johnson
> mdj at bds-soft.com
>
The SC77527P is the part number, unk if its a JEDEC assigned number 
though. The 8345 probably means it was made in the 45th week of 1983, so 
that may not match on a replacement.

I've run into several cases where a chip used in the thousands bears a 
makers number only, and if later assigned a JEDEC number, it takes a lot 
of reseach and phone calls to define. Such was the case in a $200K Grass 
Valley video switcher that grass probably made less than 50 of because 
smaller market tv stations couldn't afford it. Such small production 
stuff is very hard to source, but this chip had a faint AMD mark, so I 
took a chance and called them & waded thru a list of old hands, one of  
whom finally remembered it and that it now had a JEDEC number and gave 
it to me.  Since the GVG used around 72 of them, two at a time to build 
a 4 stage deep rubber buffer between paths in video for 8 bit control 
data, a missfire confused that whole buss, and it had 6 busses with 6 of 
these buffers for 36 total. Needless to say when I found somebody with 
dusty old stock, I ordered 4 sticks of them at 7 dollars and change 
apiece. GVG themselves were zero help, and snotty as hell to boot, so I 
learned to bypass them at every opportunity.  It had a fairly high 
failure rate, I assume from purple plague as that early pmos failure 
mechanism was called.

When I retired in the middle of 2002, I had less than a stick of them 
left.  I wrote a utility for a coco2, to reach in thru the serial port 
provided so the individual tech directors could save their "bags of 
tricks" this switcher could do, and recall them, to configure the 
switcher just before a live newscast so he/she didn't get surprised when 
a go button was pushed. The utility reached in and exercised each of 
these 8 bit wide fifo's useing 2 4x4 chips and reported if any of them 
were missfiring.  Came in very handy for later troubleshooting. I did 
that, 16x faster than GVG's $20,000 disk accessory for that storage 
function, with a coco2 and os9 level one, writing the program and 
utilities in basic09. Theirs ran at 600 baud, mine ran at 9600. No comm 
mistakes.

When that switcher was retired shortly after I left & no one could fix it 
anymore, they gave me back that coco2 with the "forgotten chip" kit I 
put in it and the two floppy's it used, one 40 DS for the programs and 
one 80 track DS for the data.  I still have it in the basement. But its 
been 17 years and my aging wet ram probably couldn't run any of it 
today.  Darn it.  They gave the switcher to a starving locsl college, 
and probably used it for a tax writeoff.  The switcher they bought to 
replace it had itself been replaced as the company went tits up long 
before June 30th 2008 when the digital switch was thrown at midnight.

One of my many war stories from nearly 50 years of broadcast engineering.
;-)

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>