I have made several ROM replacement sockets for the masked programmed
Motorola 6800 MIKBUG ROM used in the SWTPC 6800 system. The MCM6830 ROM does
not have a EPROM equivalent. The replacement board has a 74LS20 (to map the
4 enables) and a 2716 EPROM.
The challenge was to find pins that could be soldered into the ROM board
that would plug into the existing socket on the CPU board. I bought several
types of pins and headers from surplus stores and Digi-Key. I have
determined that capacitor leads are the best solution. Many capacitor lead
are made of steel and are much stiffer than resistor leads. The ones I get
>from 0.1 uf bypass caps are just the right size for machine tooled sockets.
I can make a lower profile adapter then if I use header pins.
I describe the process (with pictures) in the Users Guide on this page.
31 volumes VMS 5.0 and release 5.2 documentation in Gray DEC loosleaf
also System managers guide and Guide to VAX C
You pay shipping I'll provide the boxes. Currently in 3 boxes. I can ship
without the binders if you want smaller boxes. Pretty heavy.
c m c f a d d e n 5 a t c o m c a s t d o t n e t
I've posted (and will continue to post) a number of things I don't need
on VCM rather than EBay. Some other people have also posted some
interesting items. Some of the latest include plastic ready light covers
numbered 0 - 7 and 1 - 5 for (I think) the DEC RLO2 disk drive.
I found the manual for the Microdata machine I acquired a couple months
ago. Was it here where I was mentioning it? I forget.
At any rate, it's a Microdata Reality.
Sellam Ismail Vintage Computer Festival
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
> Hi folks,
> one simple question:
> What is that card for?
> Please don't laugh - I am a bit too young to know everything
> about strange vintage computing stuff....
It passes the bus grant signal along to the next card on the bus. Empty
slots between cards need one.
Does anyone have a list of
differences between the various versions, and what it takes to upgrade a
you may want to ask on rec.games.video.arcade.collecting
there were a bunch of people using/collecting 9010 stuff there.
Here is a story about the original IBM PC (5150) power supply. There was a
defect that showed up a few days before it was to go on sale. The design
team flew around the country adding fish paper insulation to the 1700
machines that had shipped to stores.
This is from Blue Magic by James Chposky and Ted Leonsis.(1988) ISBN
The book has a few technical errors, they mix-up 8080 and 8086 chips number
in one chapter. The refer to the modem guy as Dennis Glayes (Hayes). In this
chapter they refer to a 65 volt power supply (should be watt). The flow of
the book tells how the project was kicked off in August 1980 and you could
buy one in the store in August 1981.
Chapter 18 - The Emergency Brigade
Initial shipments of the new PC were made to Computerland outlets and Sears
Business Centers less than a week before the machine was scheduled to be
unveiled in New York City on Wednesday, August 12, 1981. The shipments were
delayed till the last possible minute to avoid leaks to the press.
Preferably, the packing boxes with the PCs inside would not even be opened
until the afternoon on the day of the official announcement. Then, on August
10, a potentially devastating discovery threatened to cancel the scheduled
introduction that so many people had worked so hard and so long to maintain.
At about 2:30 in the afternoon, Joe Sarubbi and his staff were running final
potentiometer tests to determine if there were any high-voltage leakage on
some of the new PCs. Time and again, two of the machines tested positive,
which meant that there was a possible dangerous voltage leak.
The engineers quickly found that the 65-volt power supplies on the two
machines had too close a tolerance between an electrical raw circuit board
and the frame of the power supply. This in turn caused too close a spacing
that could possibly lead to a short-circuit between the electrical current
and the metal frame. The problem was brought to Wilkie's immediate
attention. Then a quick call went out to convene the inner circle, along
with Howie Davidson, the site general manager at Boca Raton.
Sarubbi explained that the power supplies shipped to date had been tested
and were shown to be safe. But the fan in the power supply could accumulate
enough dust to create a `bridge' to the metal edge of the machine and cause
a short-circuit. In addition, a look at worst-case tolerances between the
printed circuit card and the frame revealed a tolerance that was
unacceptably close, and a relay out of the circuit board had to be added to
achieve a permanent fix for the problem. There was only a random chance that
this could happen again, but that was still more of a chance than Wilkie and
Sarubbi wanted to take. One power supply failure was one failure too many.
Meanwhile, more than 1,700 machines-all with short-circuit potentials-were
sitting innocently in storage at Computerlands and Sears Business Centers
around the country.
The IBM PC was intended to be the product to put the Sears Business Centers
on the map. Accordingly, IBM had made elaborate arrangements for a
full-scale demonstration of the machine to the retailer's senior management
committee at the Sears Tower in Chicago on the morning of Tuesday, August
11. Now, here in Boca Raton, less than 18 hours before the big demonstration
was set to begin 1,500 miles away, there was concern that the machines at
Sears Tower would not only amaze, but could quite actually shock anyone who
so much as laid a finger on their casings.
Four pairs of eyes turned on Sarubbi. Estridge was the first to speak.
"Okay, Joe, what do we do?" Sarubbi said, "We'll have to put a piece of
insulation in every machine between the printed circuit board and the power
supply cover. Fish paper, which is a non-conductive cardboard bridge, should
be sufficient, but this is something we really have to do ourselves."
Dan Wilkie suggested the formation of a quick task force. "We can call them
'The Power Supply Brigade,' and fly them out to Sears in Chicago and
elsewhere to put in the insulation. But we have to do it now-today.
Commercial flights won't get us there in time. We'll have to charter a
private jet. When they're finished at Sears, they can go back to the Chicago
airport and fly on to the next destination. Frankly, I don't see any other
goddam way we can get this done if we still plan to show the machine to
Sears tomorrow." Estridge winced. He turned back to Sarubbi and said, "Joe,
the decision to go or not to go is yours." What Estridge really meant was,
Should we stop the announcement or send out the Brigade?
Sarubbi reasoned that not to send the Brigade would mean the PC announcement
might be delayed for at least another 30 days. "That would put egg on our
face in the industry and throughout the company," he later recalled. "But
there was also no way that we could overlook the safety of the unit."
Never before in his 30-odd years with the company had Joe Sarubbi been so
overwhelmingly grateful that he worked for IBM with its vast resources and
capital. He looked back at the frantic, frustrating and yet thoroughly
exhilarating year gone by and remembered all the times he gazed across the
ocean and said to himself, "Why in the hell did I ever get into this?" Then
he pictured the other people on the project and concluded, "They're just
like me. We're all of a kind. We're wild ducks within IBM and we're doing
what wild ducks do and that's why I have to stay. "
Then his thoughts returned to the present. "Uh, Joe," Estridge said. And
Sarubbi instinctively knew what a wild duck would do at a time like this,
and so he said, "Send the Brigade. And keep the introduction just as it is."
"Well, son-of-a-bitch! All right, let's go!" Wilkie shouted as he turned
with a big grin and smacked his right fist into his ample left palm.
Estridge had to shut his eyes for a moment to pretend he hadn't heard
Wilkie, then came the famous grin. Sydnes and Davidson were also smiling,
and for that moment, Joe Sarubbi, the old pro, the veteran IBMer, the
self-professed beach bum-he was the king of the hill, at the top of the
It so happened that Wilkie had a cadre of some 30 devoted admirers on his
manufacturing staff. They were a gung-ho crowd who liked to hang around with
Dan because he had a tough side with a tender edge and he was eminently
fair. And they were loyal to Wilkie, because most of them had never worked
for anyone else anywhere else at IBM. Infants all, they thought life at IBM
was just like Project Chess, which, of course, made this a very good company
to work for. As Wilkie would later reflect, "The team's strength lay in the
fact that most of them had never really worked under the strictures of
conventional IBM standards."
Wilkie walked out of the meeting and gathered his staffers. Eagerly,
expectantly, they circled around their leader as he explained what had
happened and what had to be done. He said, "I want you guys to go home and
get your toothbrushes and a change of clothes and then come right back here
and standby to leave for Chicago tonight. You'll be going by private jet out
of Boca Raton airport at midnight. We don't know how long you'll be gone, so
he packed for at least three days." They all but tore the doors off to get
home, grab their gear and get back to the office to be among the first in
line to stand by for that emergency flight to Chicago.
As soon as the last car squealed out of the IBM parking lot, Sarubbi's
office became a war room. From this jerry-built command post, the senior
staff on the PC group arranged for a private jet to be ready to leave at
midnight for Chicago.
The plane landed at 3:00 AM on Tuesday in Chicago. Black limousines were
already waiting to whisk the Brigade through the dark streets and to the
main entrance of the world's tallest building.
Earlier, back at the war room, Sparky Sparks completed special arrangements
to admit the Brigade to the Sears Tower at that late hour. The Brigade
deployed to the demonstration room like commandos. Within three hours, their
assignment was finished; the fish paper was secured in each PC and the
machines were tested again for high-voltage leaks. The demonstration for the
Sears management could go on as planned and no one had to know what happened
in the Sears Tower the night before.
Back at Boca Raton a phone call came at about 7:00 AM from somewhere in
Chicago: "Mission accomplished!" the Brigade leader said.
Sarubbi gave Wilkie the thumbs-up sign. Wilkie went back to his own office
and took his spare shaving kit out of a desk drawer. Still not fully awake,
he stumbled into the men's room and tried to remember the last time he'd had
breakfast at home, followed by an uneventful working day.
During the next day and a half, the Power Supply Brigade, with ample
supplies of fish paper, flew to Computerland stores in Texas and California.
Once again, their missions were accomplished before the debut of the PC.
But the power supply episode was still causing upset at Boca Raton. Wilkie
recalled, "We were really paranoid about what happened. We said, `My God,
what if the world finds out that we had this quality problem?'
"In time, the world did find out, but the reaction was the exact opposite of
what we thought it would be. People everywhere were saying, `What a class
act this company has.' Sears and Computerland told us, `Now we know the kind
of treatment we can demand from all the other companies we do business
with.' And so," Wilkie said, "instead of this having a negative impact, it
became a real plus for the project and an unforgettable experience for those
men who flew around the country and worked around the clock to guarantee
that the introduction of the PC would stay on schedule."
The IBM PC introduced in New York that week had one disk drive, 16 kilobytes
of random access memory (RAM) and a $1,595 price tag. (Within four years,
other manufacturers would have a "clone" of the basic PC with two disk
drives, 256 kilobytes of RAM and it would be available for about $1,000.)
By now, despite the company's security precautions and its refusal to give
any details of the "new product introduction," enough information had leaked
out of IBM to make the purpose of the August 12 announcement well known
throughout the industry and on Wall Street. These reports were especially
significant to Martin A. Alpert in Cleveland, Ohio. Alpert, a doctor and
engineer, was president of a small company called Tecmar, a sort of anagram
for "Marty's technology.
Tecmar got its start with a computer-based machine used to diagnose lung
problems. But the company had the technology in place to build add-on
products for the basic IBM PC. Predicting that there would be an enormous
market for such add-ons, Alpert put his staff to work designing products for
a machine they had never seen. Then he made careful plans to buy an IBM PC
when it became available. As it turned out, Tecmar bought the first IBM PC
to be sold anywhere.