The IBM Tree and Tube computers

Bob Bradlee caveguy at
Sun Feb 4 11:11:19 CST 2007

The 701(1952) -> 702 (1953) -> 705-1 (1954) -> 705-II(1957) and ending with the transistorized  1401
and 701 (1952) -> SAGE, NORC, 704(1954) -> 709(1957) and ending with the transistorized 7090
and 701 (1952) -> 650(1953) and ending with the transistorized 7070(1958)
with the 305-RAMAC(1956) appearing by magic during the time between the 650(1953) and second 
generation 705 (1957). I think the computer in question was a tube computer produced in the gap 
between the first 705(1954) and the later release in 1957 a period in time where Core memory 
development was in full swing.

We were deep in the cold war at the time and a lot of mis-direction was being employed, I have always 
thought there was a tube based system that evolved between the 650 and the transistorized 7070.

It would not shock me in the least if this missing TUBE system was not refered to as a 7070 by its 
users, as one of those little cold war mis-directions Cuz-Ike's boys were so fond of, long before the 
"Real" 7070 was released in its transistorized form.

The 305 RAMAC in 1956 and along with the 705 and 709 in 1957 the 305 is considered to be the last 
tube computers produced.

So when On Sat, 3 Feb 2007 21:09:10 -0600, Jim Isbell, W5JAI wrote:

>You see the 7070 that I worked on was purchased by the US government for a
>very Top Secret installation so it may have been in use before the public
>had access to it.  Which, by the way, may also be why it was NOT solid
>state, it was an early model ??  

And questions started to roll around in my head so I looked back....
On Fri, 2 Feb 2007 15:41:07 -0600, Jim Isbell, W5JAI wrote:

>No, it was a 7070, "IBM seven oh seventy", and it used hundreds if not
>thousands of 12au7s or 12ax7s don't remember which it was.  And it was
>definitely NOT solid state.  The first solid state addition to it was a
>memory matrix unit that used germanium or silicon junctions in a plane of
>12x12 giving 144 bits of permanent memory sitting behind a plastic window so
>we could look at it and marvel at the wonders of science ( I dont think it
>was really permanent memory as I seem to remember it required a voltage
>input to keep it from fading) .  It was a frame about 12 inches square and
>looked like a course window screen with small dots of junction at every
>intersection of the wires. 

Until we can better identify this mystery system I will call it an 707x  and assume it is the
missing IBM model 707 from sometime between the 705(1954) and the 709(1957) most likely about the 
time of the 305(1956).

On Fri, 2 Feb 2007 15:41:07 -0600, Jim Isbell, W5JAI wrote:
>This was in 1959 and 1960

My first question is:
Was 1959/1960 when it was installed or when you worked on it ?

My second question is: Were the tubes in 10 pin "Fingers" like the 650 or in 8 tube plugins like the 705 

And my last questions relate to who, what and where, these questions can be answered of list, if you 
do not wish to shout it out here in an open forum :-) I understand that much if not most of what we 
could not talk about in the 60's is public knowledge but that does not keep one from thinking twice even 

Got to run ...

Bob Bradlee


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