"Oddball"

Sridhar Ayengar ploopster at gmail.com
Fri Jun 29 04:28:23 CDT 2007


Christian Corti wrote:
>>> Some other oddball values from that era:
>>>   - BINAC: 31 bits
>>
>> I don't know if you can call 31-bit "oddball".  IBM literally made 
>> thousands upon thousands.
> 
> And don't forget the LGP-30 (450 built in total, 45 built in Germany) 
> and compatibles (LGP-21, ...). Its word size is officially 32 bits, with 
> only 31 bits usable (only the accumulator can hold all 32 bits, once 
> stored on the drum the LSB is forced to zero). So I call it a 31-1/2 bit 
> machine. And its design is marvelous, a CPU with all four basic 
> arithmetic functions (fixed point) that contains only 15 flip-flops.

Well, even the IBM machines had a full 32-bits per data word, but 
addresses were 31-bits.

In any case, the LGP-30 (and LGP-21) were far (25+ years?) earlier than 
the 370-XA machines.  If memory serves, IBM didn't come out with 370-XA 
until the early to mid '80s.  But I wasn't kidding when I said they sold 
thousands upon thousands.

Peace...  Sridhar



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