18 bit CPU; was: Speed now & then

Bill Gunshannon bill.gunshannon at hotmail.com
Thu Apr 12 06:48:20 CDT 2018

On 04/12/2018 02:45 AM, Chuck Guzis via cctalk wrote:
> On 04/11/2018 06:38 PM, Chuck Guzis via cctalk wrote:
>> On 04/11/2018 02:48 PM, ben via cctalk wrote:
>>> I have a nice 18 bit cpu here, with only a few hardware bugs.
>>> Hmm would it work better if I change that around ideas.
>>> Care to point to a nice 18 bit version of unix or C.
>>> BTW The cpu has a frame pointer S but no S++ --S operations
>>> so pushing and popping wild data is not a option.
>> Well, the Univac 1100/2200 series mainframes ran V7 Unix--and they're
>> 36-bit machines, so probably not far from your 18-bitter--and they're
>> ones' complement machines.
>> Univac called it "SX1100", so you have a search term.
> Remarkably, Unisys keeps a lot of old documentation around.  Here's the
> reference manual for their "C" on th 1100:
> https://public.support.unisys.com/2200/docs/cp14.0/pdf/78310422-011.pdf
> Looks pretty much like standard C until you get into the minutiae, such
> as "A character constant is 1 to 4 characters" and page 4-4 "Data Types"
> (9 bit characters and 36 bit ints and 18 bit short ints).
> So, it should be pretty straightforward unless you assume that a char is
> 8 bits, with a signed char having a range of +/-255.

Signed 8 bits would be  -128 to +127.


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