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360/85

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I think we had some discussion here about the 360/85 quite some time ago.

There seem to be a few bits of info on the net that are wrong, indicating 
that the /85 used ASLT components.  I finally ran across something more 
definitive.

"IBM's 360 and Early 370 Systems"  By Emerson W. Pugh, Lyle R. Johnson, John 
H. Palmer

This book indicates the model /85 was the first to use MST-4 chips, same as 
the 370/165.

As soon as I came across the incorrect technology reference, I suspected it 
couldn't be right, as the model /85 had 500 words of writable control store.
500 words of 108 bits is 54,000 bits.  With ASLT being made of discrete 
transistors on double-stacked SLT ceramic substrates, and assuming a storage 
bit could be squeezed into 4 transistors, that would be over 200,000 
transistors.  That would be a HUGE chunk of hardware, and just doesn't make 
sense.

With the info that the /85 was using MST-4 (and the earliest memories were 
made with 16-bit ECL chips) you could get this down to ~3400 chips.  If you 
put 2 chips into each MST package, that would fit in 1700 packages, and 
maybe could be packed onto about 100 small MST cards.  While that is a 
pretty big piece of hardware, it makes sense it could be fitted into such a 
machine.

Another reason I suspected that the /85 and /165 were VERY similar is if you 
look at the instruction timings, they appear almost to be the same pages, 
duplicated.  the timings for almost EVERY instruction is identical down to 
the same number of clocks.

Jon

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360/85 Jon Elson <elson@pico-systems.com> - 2016-01-19 23:51 -0600
  Re: 360/85 Quadibloc <jsavard@ecn.ab.ca> - 2016-01-20 03:13 -0800
    Re: 360/85 Jon Elson <elson@pico-systems.com> - 2016-01-20 12:09 -0600
      Re: 360/85 Anne & Lynn Wheeler <lynn@garlic.com> - 2016-01-20 10:26 -0800
      Re: 360/85 Quadibloc <jsavard@ecn.ab.ca> - 2016-01-20 10:40 -0800
        Re: 360/85 scott@slp53.sl.home (Scott Lurndal) - 2016-01-20 19:43 +0000
        Re: 360/85 Jon Elson <jmelson@wustl.edu> - 2016-01-20 13:55 -0600

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