Re: booting NetBSD/vax on real hardware

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

On May 27, 2014, at 7:33 AM, Anders Magnusson <ragge%ludd.ltu.se@localhost> 
wrote:

> Martin Husemann skrev 2014-05-27 13:27:
>> On Tue, May 27, 2014 at 12:33:12PM +0200, Martin Husemann wrote:
>>> Spot on - not the decompress code, but the crc32() function in libsa.
>>> The optimized one in libkern uses large tables, but that makes it fast
>>> on VAX. The tiny one in libsa computes it all on the fly - and seems to
>>> be dog slow on VAX.
>>> 
>>> I'm testing a change to switch back to the libkern one for VAX.
>> Unfortunately that didn't do the trick. But still we should have an
>> asm version of crc32 using the crc instruction. Anyone?
>> 
> Hm, is the crc function available on all CPUs?  So that we do not end up 
> emulating it on some hardware?

The VAX architecture manual says it’s optional, and Appendix B seems to say 
that specifically it is omitted on the MicroVAXen.  It might be interesting to 
use a fast large table version on those, and the machine instruction where it 
exists.  (That assumes the large table version is actually fast; given machines 
with small caches that might not be true at least once the cache is enabled.)

        paul