vacuum tube computer

From: Jgzabol_at_aol.com <(Jgzabol_at_aol.com)>
Date: Mon Feb 1 07:30:03 1999

In einer eMail vom 31.01.1999 23:58:22, schreiben Sie:

<<
 I wonder if bit-serial would be simpler (less data path, more control
 logic, basically). A lot of the valved machines were bit-serial for this
 reason.
 [...]
 
     I simply find bit-serial AWFUL - so much time wasted !!! Anything
     should be designed to get the max. performance out of given
     technology/budget, in my opinion; bit-serial certainly then would be
    a good solution for a LONG word, like 30-60 bit, doing floating point,
     if and only if budget limits do not allow paralell,
     but not for smaller things. THAT is the reason for the historic machines
     - they wanted floating point, therefore long words, therefore serial
because
    of budget/size/etc constraints.

> Am amazed you couls build a computer like this with ~400 cards ~800 tubes.
> That is similar to building a complete computer with 200 SSI TTL chips like
> a 7400. Especially since a 24 bit latch could use 24 of the cards. I tried
 
 This doesn't sound out of line. The CPU of the PDP8/e on my desk is 3
 quad cards of TTL, mostly simple gates. Perhapes 250chips total. OK, some
 of them are more complex (like full adder circuits), but there's nothing
 that big in there.
 
> a design once (on paper) with MSI ic's like 74193 counters, and it quickly
> got out of hand, 100's of ic's.
 
 If you're going to allow anything in the TTL data book, then you can
 trivially make a CPU in 200 chips. You have to cheat slightly (74181
 ALUs, small PROMs, etc), but it can be done. It has been done - many times.
 
 
 -tony
 
>>

       The big difference is in the basic AND-OR-INVERT tube gate used: only
       one half tube (the INVERT, one triode section out of a dual triode
tube) is used,
       but a lot of diodes doing the ANDs and ORs,
       so that one tube section is equivalent to MORE than a standard SSI 74xx
IC.
      Typically, I would say one AND-OR-INVERT, i.e. one tube section
      plus associated diodes and resistors is equivalent
       to about one entire 74xx package, so one tube is equivalent to about
two
      packages, on the average.

John G. Zabolitzky
Received on Mon Feb 01 1999 - 07:30:03 GMT