Re: Does the KA630 have a TB?

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

>>>>> Why not cache entries outside main memory, by the way?
>>>> [...JIT...]
>>> [...]
>> [...] cache (faster-to-access forms of) PTEs for virtual addresses
>> that map to main memory, but nothing else [...]
> The first lookup (which is what would go through the TB if an entry
> exists there) is what always have to happen.  [...] just caching so
> that you don't have to go via the PTE in case there is a TB hit seems
> like always a win.  I don't see any gain in just not caching some
> entries.  Or, hmm.  Ok, so you know that if you hit in TB, it's
> memory.  So you can skip one compare after the TB lookup in that
> case.

Hm, true, it is just the one compare.  Well, a load-from-memory and a
compare, but the load from memory is likely to hit the (real) CPU's
cache, because the VAX goes to memory frequently.

I hadn't thought it through enough; thank you.

>> Well, the 1.4T kernel I'm working with definitely uses 4K pages.
> Change was back in 1998-08-21.  Thanks for just reminding me how old
> I'm getting. :-)

I know the feeling, I know the feeling.  Just recently I had someone
tell me I'd been writing C longer than he'd been _alive_.

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