Interested in UNIVAC 9000 Series (and IBM 360)

Charles Dickman chd at
Mon Nov 21 12:28:26 CST 2016

On Sun, Nov 20, 2016 at 7:29 PM, Jon Elson <elson at> wrote:
> 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 impression.
> Jon

I was looking here:

(pdf) pages 45, 46 describe the ALU

And here:

(pdf) pages 15 and 38 Data flows and ALU schematic

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