[THIN] Re: Quick PAE question
- From: "Malcolm Bruton" <malcolm.bruton@xxxxxxxxxxxxxxxxxx>
- To: <thin@xxxxxxxxxxxxx>
- Date: Thu, 8 Mar 2007 04:34:02 -0500
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From: thin-bounce@xxxxxxxxxxxxx on behalf of akash mehta
Sent: Thu 08/03/2007 04:25
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Quick PAE question
Hi!!
Please can anyone of you tell me how to Unsubscribe from this group Please
send me URL for same if any present.
Thanks in Anticipation.
Aakash R. Mehta
Support Engg.,
IT Division,
The Jewellery Store-DMCC
Dubai.
Tel: +97-14-2350489
Mo: +97150-4682636
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From: Toby <toby.percival@xxxxxxxxx>
Reply-To: thin@xxxxxxxxxxxxx
To: thin@xxxxxxxxxxxxx
Subject: [THIN] Re: Quick PAE question
Date: Thu, 8 Mar 2007 09:17:31 +0000
Is this what your talking about?
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=PSD_EL041214_CW01
Thanks,
On 1/13/07, Rick Mack <ulrich.mack@xxxxxxxxx> wrote:
Hi Michael,
It depends on the hardware and bios version.
By convention the PCI address space is put on top of the 32 bit
address space, so the CPU can "talk" directly to the PCI registers and memory
arrays. Now we've also got PCI Express which sits above the PCI address space.
Multiple PCI busses can extend this usage as well.
If you've got hardware designed (or bios, see below) for 32
bit/4 GB, the PCI/PCI express address space is above 4 GB and is basically
invisible because it's not in your normal 4GB RAM address space.
Where you've X64 hardware designed for more than 4 GB of RAM,
then the convention is to drop the PCI/PCI Express memory space down to between
3.5-4 GB (generally PCI at 3.5 to 3.75, PCI express at 3.75 to 4 GB). The RAM
you bought is all there but you've got a distribution like RAM [ 0-3.5 GB], the
PCI/PCIE hole [3.5-4 GB] and then the rest of your RAM [4-4.5 GB]. Since the
"normal" o.s. (not PAE or enterprise) can only see physical RAM to 4 GB, it now
appears as a memory hole.
If you've got PAE then the o.s. can use RAM above 4 GB so it
can "see" the extra 500 MB above 4 GB and you've got your 4 GB back.
When the 64-bit capable systems first started coming out, a lot
of people complained because they were losing at least 500 MB of useable
memory. So manufacturers either "fixed" the bios to move the memory hole back
up "out of sight", at least for Intel CPUs. I believe AMD CPUs have a fixed
hole at 3.5-4 GB so there's no bios fix, just PAE.
So you've got at least 3 variables, motherboard design, bios
revision and cpu type that can affect what you see without PAE. With PAE it
doesn't matter.
So is /PAE a good thing? I'd have to say yes since it gives you
at least another 500 MB of useable RAM on your 4GB RAM systems.
regards,
Rick
On 1/13/07, Michael Pardee <pardeemp.list@xxxxxxxxx > wrote:
I don't remember the final answer, but was /PAE a good
thing or a bad thing?
We have a couple hundred IBM HS20 Blades, and on some
Blades that OS sees all 4GB of memory and on other it may see 3.2GB or 3.5GB of
memory. Same BIOS version on most. Adding /PAE we see it all but for some
reason I remember this being a bad thing instead of a good thing to do.
Windows2003 Standard Edition with SP1.
Thanks in advance.
--
Michael Pardee
www.blindsquirrel.org <http://www.blindsquirrel.org/>
--
Ulrich Mack
Commander Australia
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