Re: VAX floating point formats & tuning GCC for CPU models (was Re: Some more patches for GCC...)

[Paul Koning <paulkoning%comcast.net@localhost>]

> On Apr 4, 2016, at 12:45 PM, Antonio Carlini <a.carlini%ntlworld.com@localhost> wrote:
> 
> On 04/04/16 17:05, Felix Deichmann wrote:
>> Am 04.04.2016 um 17:58 schrieb Mouse:
>>>>> [...] NetBSD on VAXen without FPA chips, [...]
>>> 
>>> I'm probably just exposing my ignorance, here, but, do such things
>>> exist?
>> 
>> InfoServer 1000 for example. It seems to be based upon a CVAX 78034 CPU without the "floating-point accelerator" CFPA.
> ...
> That said, I don't know whether any real VAX ever shipped without FP. The VAX-11/730 was, iirc, almost entirely implemented in microcode, so I guess you could re-write the microcode and dump the FP instructions. Not sure that would count as a VAX though ...

The "VAX Architecture Reference Manual" book (not the DEC internal document) has summaries of the various models in Appendix B.  I though that Microvax I was an exmaple of a no-float machine, but that's incorrect.  What it says is that there were two versions: one with F/G and one with F/D.  (Neither variant has H float.)  MicroVAX II is shown as having F/D/G but no H.  It also says, interestingly/curiously enough, that G/H float support was an optional feature on the 750 and 780.  Also that the 730 was the first VAX to have F/D/G/H standard.

	paul