Re: S/360

Well those options were in the proposal Cray sent to RPI around 
1974/1975 when RPI was looking to replace their old 360-50.  Those 
numbers came from the Cray proposal.  It is possible that at the time of 
the proposal those were options and later things changed.  I don'tknow 
how many Cray's had been delivered at that time.  Around 1976/1977 the 
RPI-ACM had a guest lecturer from a site with a Cray or had worked at a 
site with a Cray.  The comment I remember most was the MTBF was about 4 
hours and the MTTR was about 10 minutes (the time to wiggle all the
boards).

Dan Nagle wrote:
> Hello,
> 
> multicsfan wrote:
> 
> <snip>
> 
>> The Cray-1 did not initially come with hardware divide, the divide was 
>> done in software in the pipe.  Hardware divide was a $500K option 
>> which was slower then the software divide ;)
> 
> 
> No Cray-1 ever had hardware divide.
> Floating point divide was always a reciprocal approximation,
> followed by correcting multiplications.  A special 2-a.b instruction
> applied part of the correction.
> 
>> Memory Parity was also a $500K option.  To check for memory errors the 
>> idea was the Cray was so fast you could just run your program twice 
>> and if you got the same answer there was no memory problem.
> 
> 
> Serial #1 Cray-1 had no parity, Serial #2 was being built without parity
> but was scrapped before completion.  Serials #3 and beyond
> all had SECDED.  It added one clock to scalar memory fetch times,
> raising it from 10 to 11 cp.
> 
> The only options ever available on the Cray-1 was how much memory
> the customer wanted to buy.  (Modulo peripherals, of course.)
> Most were sold with 1 MW, from 256 KW to 4 MW was
> theoretically possible.
>