18b computers

Chuck Guzis cclist at sydex.com
Fri May 22 03:39:47 CDT 2009

On 22 May 2009 at 1:59, bfranchuk at jetnet.ab.ca wrote:

> Well this is new 18 bit computer I have heard of ... I guess more on
> topic than say a PC clone. > > 

The A and B registers in a CDC 6000 series machine were 18 bits (CPU 
word was 60 bits).  Eventually, this created problems, when more than 
128KW was available on a CPU (lots of code used signed addresses to 
signify this and that.  Conditional branches were performed on the 
sign or contents of a register, not on a condition code, so it could 
get a little tricky doing 18-bit unsigned comparisons).

There were, however,  plenty of 36 bit mainframes from various 


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