Re: rtVAX300 .. adding an CPU Type..

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> I've looked closer at the two Memory SIMMs that are on that rtVAX300
> Board.  [...]  So the entire memory is 4MB + 16bit Parity.

> Is that enough to run a NetBSD kernel over NFS?

Probably.  I don't know whether it'll run modern (whatever that means)
NetBSD/vax, but at worst you'll need to work on an older version.  I'm
fairly sure there'd be space for the 1.4T I run on those of my machines
that I can, for example...but maybe not for a whole lot more.  I recall
running 1.4T on a 5MB hp300 machine, and, while it ran, there wasn't
much RAM left for user processes.

> The rtVAX 300 implements the full VAX memory management [...]

Okay, so we don't have to worry about KA620-style issues; the existing
VAX pmap should work fine.

> 3.1.8.1. Translation Buffer

> To reduce the overhead associated with translating virtual addresses
> to physical addresses, the rtVAX 300 processor employs a 28-entry,
> fully associative translation buffer [...]

> ...whatever this means...

Not much, from a programmer's perspective.  As I read it, it just means
you have to be careful to use TBIA and/or TBIS whenever you change
PTEs, which is something I would certainly hope every version of
NetBSD's VAX pmap already does.

I can go into more detail if you like, but, in short, I don't think
this is anything you need to care about.

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