On 01/23/2017 09:04 PM, Chuck Guzis wrote:
On 01/23/2017 05:45 PM, Jon Elson wrote:
WOW!!!! That is QUITE amazing! And, I can't possibly imagine why
anyone in their right mind would do this! Seems an emulator on a PC
would be faster, and way more reliable, not to mention taking up MUCH
less space, power and cooling. How reliable can a 60 year old
machine possibly be? Where do you get parts? There have to be a
whole lot of special parts that are deteriorating, like the plastic
parts on the console. Even the PC boards (IBM SMS cards) are pretty
fragile, easily damaged during rework, and some of them dissipate a
lot of power, causing slow thermal degradation.
Are we SURE this isn't a preview of the April 1st edition?
I wondered about this too. Even the USAF eventually replaced the 7080s
with S/370 running emulation. Keeping a 7074 running (if my memories of
keeping a 7094 going are accureate) would be quite some task.
Yes! There's all sorts of little things that would drive
you nuts. Things like cooling fans, power supply capacitors,
cable routing hardware (clamps, ties, etc.) that they no
longer make. it would be a constant job of finding suitable
replacements for unavailable parts. The 7000 series had
"pages" that made up a "book" with tons of old wiring that
flexed every time you opened up the pages to access the
circuit cards. I just CAN'T believe somebody is actually
keeping such a machine in daily service. (On the other
hand, CHM does have a working 1401, that also requires
folding out racks of boards to access the cards, flexing
similar cables.)
Wikipedia says the 7070 had 14,000 SMS circuit cards, with
30,000 transistors and 22,000 diodes. Having worked on some
much more recent gear with Germanium transistors, I saw
about 10% of them were bad. I didn't run that gear long
once I fixed it, I sold it on eBay before any more went
out. But, I can't imagine that a machine with that many
components could keep running awfully long between failures.
As for the 1-6 ms response time, that is totally bogus. The
article is complete gibberish, talking about a vast library
of mag tape and ms response time in the same sentence.
Maybe the 7074 prepares data weekly for some other (newer)
system that is actually connected online. And, of course,
to connect anything to the 7074, you'd have to build custom
hardware. RS-232 had not even been invented when the
7000-series came out. They did have a 1414 unit that
apparently was some kind of comm adapter, but I'll bet it
took milliseconds to send one character.
Oh, and the picture in the article is CLEARLY a posed IBM
sales brochure photo, and not from the recent operation at
the unnamed government agency.
Jon
