K.S. Bhaskar on 8 Mar 2008 14:08:34 -0800

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Re: [PLUG] Virtualization Presentation

On Sat, Mar 8, 2008 at 8:41 AM, Mag Gam <magawake@gmail.com> wrote:
> Whoa, you are a dinosaur sir ;-) Kidding

[KSB] Not far off the mark!  The first computer I used was an IBM 1620
model 1.  RAM was 40,000 decimal digits.  The basic cycle time was 20
microseconds, and it took a minimum of 8 cycles for an instruction.
So to add 2 and 2 to get 4 took 160 microseconds (the model 2 had a 10
microsecond cycle time and took a minimum of 6 cycles).  When IBM
first came up with the 1620, it was to be called the CADET.  Then
someone pointed out that CADET is an acronym for "Can't Add and
Doesn't Even Try".  This was true - it didn't have addition hardware.
Adding two decimal digits was accomplished by putting one digit in the
units place of the address and the other in the tens place.  Hardwired
into memory locations 200-299 was an addition table, so location 267
contained a 3 with a flag bit to indicate a carry.  Ever since then,
IBM has used numbers for computers (at least till "PC" came along).

I also spent a year of my life programming a PDP-1 (serial number 45
or 48 - I forget).  18-bit words, of which 5 bits was the instruction,
1 was an indirect bit and 12 bits was the address.  It was the
architectural ancestor of the PDP-8 that some on this group may
remember.  This particular machine had been extensively modified by
Stanford, and had its limited instruction repertoire added to with an
instruction called FFI - Fiddle Following Instruction - which could
cause the subsequent opcode to do something completely different.

One of my projects started out with a quartz delay line memory.  You
put a bit in at one end and it came out 10msec later at the other end
and had to be fed back in to keep the bit alive - the intellectual
predecessor of the dynamic RAM.

Dinosaurs are positively modern, in comparison!  Thanks for the
opportunity to reminisce.

-- Bhaskar
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