Re: Moving VAX into 21 century :-)

[Dave McGuire <mcguire%neurotica.com@localhost>]

On 8/26/19 8:08 AM, Anders Magnusson wrote:
> I have been looking at some VAX problems lately, and have found out that
> there are two architectural things things that probably would help VAX
> quite much.
> 
> 1) Change calling convention.
>     As described in my previous mail, it would solve a very old
> well-known performance problem.
> 
> 2) Make VAX use IEEE floats :-)
>     Today virtually no floating point exist that is not IEEE.  The only
> fragment around is probably the VAX floats.
> 
>     I have done some checking, and if we accept the difference in
> rounding (VAX uses a different way than IEEE) then it would be (almost)
> no overhead in the common cases (overhead comes when dealing with INF,
> NAN and subnormals).
>     - Use F and G floats.  They have the same format as IEEE single and
> double, and are both available on virtually all VAXen.
>     - Make use of the floating point faults that VAXen can generate to
> emulate the features missing on VAX.
> 
>     ...in theory also H floats could be used as long double since they
> match the IEEE 128-bit quad precision :-)
>        But since H float is optional it might end up being emulated
> (maybe not a big problem?)
> 
> Comments on this?

  My only comment is "YAY!"  I'm very happy to hear that your passion
for VAX has been rekindled. :-)  I'd welcome a performance improvement,
as well emulated IEEE FP support.  Thanks for even thinking about this,
Ragge, and I hope you find the time to proceed with this.

           -Dave

-- 
Dave McGuire, AK4HZ
New Kensington, PA