[rescue] systems with user modifiable microcode.

[dave at cca.org]

dittman at dittman.net writes:

>I tend to think of PALcode as macromicrocode.  It does serve
>to add missing features and cover over incompatibilities with
>the OS, but the level really is above microcode.  I'd consider
>it kind of an emulation layer.

Am I correct in thinking that PALcode doesn't actually have
access to any instructions that aren't already accessable
though? It's more like library routines than microcode. I'm
guessing a major feature is that you can make a series of
instructions atomic by using PALcode? That would seem to be
important when it comes to playing with the MMU and such...

>Over time the need for some of the VMS PALcode has been negated
>by changing the low-level code.  For the Itanium development,
>even more of the low-level VMS source has been changed to make
>VMS more architecture-independent.  One of the goals during the
>Itanium development is to make VMS very easy to port to other
>architectures, particularly POWER4.  If I can't have EV8 and
>above, I'd much rather have VMS on POWERx than Itanium.

WOAH. That rumour I had not heard. VMS on POWERx would be 
most interesting.

------ David Fischer ------- dave at cca.org ------- http://www.cca.org ------
------------------------ Drink Your Ovaltine! -----------------------------