Subject: Re: VAXstation I questions
To: None <>
From: Brian D Chase <>
List: port-vax
Date: 06/27/1999 16:30:57
On Thu, 24 Jun 1999 wrote:

> UvaxI is the smallest instruction subset of the whole bunch and that
> compile estimate may be off by a few days. ;)

Just wanted to clarify this a bit.  The MicroVAX I always seems to be
negatively portrayed as having a terribly reduced instruction set.  The
only thing that's really hurting it are its limitations in floating point.
The MicroVAX I only shipped with F_float and D_float or F_float and
G_float. Whereas the MicroVAX II supports F_float, D_float, and G_float.

HOWEVER, the MicroVAX I does support the optional CMPC3, LOCC, SCANC,
SKPC, and SPANC instructions which the MicroVAX II does not support.
[pp 538-539, VAX Architecture Reference Manual, 2nd Ed.]

The NetBSD/vax C compiler only generates F_float and D_float ops
as that appears to be the lowest common denominator of VAX floating point.
The only exception being the slim 10% of all MicroVAX I's sold which came
in the F_float/G_float flavor.  Which is what mine is :-/

So if you're excluding the FP stuff, the MicroVAX I has more instructions
than the MicroVAX II.

Brian "JARAI" Chase | | VAXZilla LIVES!!!