Interested in UNIVAC 9000 Series (and IBM 360)

Jon Elson elson at
Sun Nov 20 18:29:20 CST 2016

On 11/20/2016 05:30 PM, Charles Dickman wrote:
> On Fri, Nov 18, 2016 at 6:15 PM, Jon Elson <elson at> wrote:
>> OH, yeah!  Besides the limited instruction set, short registers only half
>> populated, etc., did you know that the 360/20 did not have an adder?
> This made me curious about how primitive it was, but the FE docs on
> bitsavers show a 16bit ALU that can do ADD, AND, OR and XOR and maybe
> some logic to help with BCD math.
OK, in this manual :

They describe the functions available in microcode.  They 
are REALLY limited!
See Page 1-23, Description, item 4.  They have data transfer 
and increment and decrement.
Period!  I don't see ANYTHING that relates to ALU 
functions!  Maybe I missed it, it seems really hard to believe.

and then page 1-27 describing what the increment and 
decrement commands do.  Notably, they note that the 
registers contain values from 0-15, ie. a 4-bit field.

Maybe I missed the whole point of what they are describing 
here, but this seems to be somewhat consistent with what you 
can pack into a 16-bit microinstruction, namely, not a lot.

Take a look in this manual and see if you get a different 


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