Got a question....PDP? VAX?

From: Mike Ford <>
Date: Fri Mar 12 19:53:18 1999

>I've been growing up in the age of "IBM era" of computers. The only non-IBM
>(compatible) computers that I've worked on was an apple //c and a TRS-80
>model III that nearly caught my basement on fire. I'm 16 years old, so I
>haven't had any experience with any pre 1980's stuff (other than the //c).
>What I'm wondering, is what exactly is a PDP, or a VAX, or an Altair, or any
>of the other things that come up frequently on the list. Also - how is one
>of the computers (such as the Altair) operated, with all the switches and
>indicators? Is there a keyboard or a monitor with it?

Wow, do you want the one or two paragraph history of computing as we know it?

Maybe Moore's law explains it best, every couple of years computers get
twice as fast, for half the money and size. Now Start with a typical
present day Pentibum II 400 Mhz 128 MB ram 10 GB hard drive that sells for
$2000 and go back in time 20 years (about 10 of Moore's cycles). Computers
were 1000 times slower, bigger, and more expensive. That was a different
world, and you had to treat such valuable resources differently. People,
and really only a small favored few, had to share the computers, and time
24 hours a day was highly prized.

Around 1970 a computer about as powerfull as a present day $100 calculator
cost about $10 million and required a large secure and temperature
controlled room. That was the mainstream of mainframe computers. The
computer was the size of a kids play house, and all around it in the large
room were "peripherals" designed to keep the main cpu busy working all the

Away from the main IBM oriented data processing shops, dozens of smaller
companies fought for the minicomputer market. Smaller, and less powerfull
in absolute terms, these units were targeted at the scientific and
industrial users who needed the computational or control that only
computers allowed. Minicomputers weren't that different from mainframes,
just scaled down in some senses, and optimized in others.

Digital Equipment Corporation, DEC was one of these minicomputer companies,
and its PDP line was hugely popular in many areas. Industry, banking,
telephone, and most important universities. The DEC PDP series became the
platform that many computer scientists experiemented on, and many students
still didn't get to use. As Moores law improved the lot, the VAX line came
out, and people logged on with gusto forever after.

Oh, those switches and lights are mostly because the hardware and software
used to screw up fairly often, and by looking at the lights, and flipping
switches the operation of the computer could be single stepped (one
instruction per button push) and errors identified so they could be
Received on Fri Mar 12 1999 - 19:53:18 GMT

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