[CentOS] [OT] Memory Models and Multi/Virtual-Cores -- WAS: 4.0 -> 4.1 update failing

Sat Jun 25 01:14:25 UTC 2005
Bryan J. Smith <b.j.smith at ieee.org>

On Fri, 2005-06-24 at 20:16 -0400, Peter Arremann wrote:
> Ok - so the PAE36 mechanism is the same, the 36bit addresses are the same just 
> the address ranges that are reserved for special use are different? 

Ugh, sigh, you're thinking like a programmer.  ;->  You have to separate
the logical (programmer) from the physical (engineer) concepts.

> Sorry meant beyond 32bit address space / 4GB. 

Right, I understood that.
I was just wondering if you meant beyond 36-bit/64GiB as well?
Because EV6 is 40-bit/1TiB.

> That would require an additional level of page translation though or a really 
> substential redesign - so its in my opinion unlikely that they do...

Again, thinking like a programmer.  ;->

The Athlon was _already_ designed for 40-bit EV6 _physically_ and
eventual "Long Mode" programmatically.  The TLB in the Athlon is _not_
designed for GTL, but EV6.  It only works like a GTL when so
commanded.  ;->

> GTL (P5) yes - but that doesn't have PAE36 either... But we're talking PAE 
> here - so GTL+ aera...

I meant GTL and all derivatives ... GTL+, AGTL+, etc...

> The address pins are even labeled up to A35 Download any of the PPro and
> newer spec sheets (except mobile cpus that don't support PAE). The
> Pentium II 300Mhz Specs is a good example. Quote from page 75: "The
> Address signals define a 2^36-byte physical memory address space." 
> document id 24365702.pdf

Of course!  Because if it didn't, it wouldn't be able to page in beyond
4GiB.  @-ppp  Yes, but the TLB compatibility and other issues are
involved, things that GTL and all derivatives _never_ addressed.

In a nutshell, Intel PAE36 processors on even AGTL+ are _incapable_ of
the combination of both _physical_ and _logical_ addressing to do
anything but paging above 4GiB.  That's my point.

AMD solved the problem by using EV6, which is _nothing_ like GTL-based
busses.  It goes far deeper than you realize.


-- 
Bryan J. Smith                                     b.j.smith at ieee.org 
--------------------------------------------------------------------- 
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