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== "Paging and Virtual Memory" == == PAE Xeon only ==

Anyone reading this article should have at least a basic understanding of the concept of ] in my opinion. And perhaps more importantly, the added section ''still'' requires such an understanding, because it provides no explanation of what paging and pages are to other readers. Therefore I don't see it as an improvement. It also seems to be copied and pasted from the source (judging from the excessive line breaks) and therefore not allowed.--] ] 19:40, 10 April 2017 (UTC)

:It also didn't " how PAE works in IA-32" - the only thing it said about PAE is that "IA-32 architecture’s paging mechanism includes extensions that support Physical Address Extensions (PAE) to address physical address space greater than 4 GBytes." That says what PAE does, but doesn't say how it does it. The article ''already'' says what it does (in the lede, it says " It defines a ] hierarchy of three levels, with table entries of 64 bits each instead of 32, allowing these CPUs to access a physical ] larger than 4&nbsp;]s (2<sup>32</sup> bytes)."), ''and'' it later says how it does it (a quick mention in "Design", and a long description in "Page table structures"). ] (]) 19:55, 10 April 2017 (UTC)

:: I'm glad I'm not the only one. I couldn't see where it "explained how PAE works" at all.
:: Worse: As suspected by Jasper Deng, the disputed material is a direct copy from volume 1, section 3.3.2, of the . There is no doubt or ambiguity about that. The editor even copied the bulleted list from the Intel book as if it was ordinary text, resulting in "inline bullets". I have left a copyvio warning on their talk page.
:: What is especially odd here is that the same editor, {{userlinks|PastieFace}}, had previously what was basically a CN tag on ], claiming that a cited reference referred only to the Pentium Pro and that any statements about later processors were CN. Yet this editor is clearly aware of this Intel reference which defines PAE as part of the IA-32 architecture, not specific to any processor.
:: Both of these articles have been the target of much harassment over the last few years. I note that these recent instances happened shortly after I got a from our old friend and long-time sockpuppet Janagewen. Whether there's a connection there or not, I think PastieFace's future attempts can be ignored on ] grounds, and should be checked for ] as well. ] (]) 07:59, 11 April 2017 (UTC)
{{ping|PastieFace}} If you bothered to look at the section on "Operating system support" you'll see that it's ''not'' a Windows-specific thing. And virtual memory has everything to do with it: each virtual address space remains 32-bit even if the physical memory is bigger, as your edit even mentions. If you do not have a good understanding of this concept, I suggest you avoid this topic.--] ] 20:28, 12 April 2017 (UTC)

:Furthermore, if you don't have paging virtual memory enabled, PAE doesn't even exist - PAE involves a modified form of the page table, with larger page table entries capable of providing more bits of physical address, expanding the physical addresses generated for virtual addresses from 32 bits to 36 bits. ] (]) 20:45, 12 April 2017 (UTC)
:: And wider on x64 processors while in long mode. ] (]) 21:11, 12 April 2017 (UTC)

:Further²more: PF claims PAE is Intel-only. That is wrong. PAE has been supported by AMD CPUs since the Athlon (K7) and continues in the K8, even when the latter is in legacy mode (ie running as an x86 CPU). It is true that AMD's support for PAE came several years later than Intel's: Intel had it in the Pentium Pro, late 1995, while AMD didn't have it until the Athlon, mid 1999.
: So, yes, for a time, Intel supported PAE while AMD did not. But that time ended ''over 15 years ago!''
:I wish I could quote a K7-era AMD Architecture manual, but I can't find one. The oldest I have is the original hardcopy set for the AMD64 architecture, which does show that PAE is available on the K8 in legacy mode, but that isn't definitive for the K7. The online sources I've found are more recent still, but one would hope that they would at least disabuse PF of the notion that AMD doesn't support PAE at all on ''any'' platform. (See , section 5.2.3 for legacy mode. For long mode, see 5.3: ''"Because PAE is always enabled in long mode ..."''
: On the bright side, PastiF's mistaken ideas have suggested to me a new diagram that may eliminate misconceptions like ''" once a process hit the 4GB limit, IA-32 CPU would start paging in and out of RAM using internal registers., that's what PAE is."'' (from PastieFace's to my talk page) (No, the CPU does not do that, and that isn't what PAE is.) ] (]) 21:11, 12 April 2017 (UTC)

:: I'm not sure AMD had an overall ISA manual before AMD64, as the ISA they implemented was "IA-32, possibly without the latest and shiniest Intel extensions, but with some of our own extensions such as 3DNow!", and they may just have expected developers to rely on Intel's ISA documentation plus their supplemental documentation on extensions such as 3DNow!. I tried digging through the Wayback Machine's early-2000 archive of amd.com, but at least one PDF document they had didn't fully download and, if I tried downloading it from the command line, neither ] nor the latest version of Acrobat Reader for Mac can open it (they both report it as damaged). ] (]) 01:48, 13 April 2017 (UTC)

::: The infamous table at ] says the K7 has PAE, but the claim is not referenced. ] (]) 02:53, 13 April 2017 (UTC)
::: Correction... it's referenced now. *grin* ] (]) 10:14, 13 April 2017 (UTC)
:::: Thanks! I've copied that reference to this page as well. ] (]) 10:27, 13 April 2017 (UTC)
You guys can try and gang bang me and babbletalk all you like, it won't phase me. Actually I expected this.
Some of the comments here read like the MSDN library articles on Windows Memory limitations which neither my peers or myself have able to decode as yet...
The tech writers did their jobs well. Obfuscation is 2nd nature to developers. Easy to ignore it however since some of us rely on empirical evidence for answers.

@Jasper - 1st comment I said it is specific to Windows and Intel.
1: There is PAE designed by and implemented by Intel on architecture which allows processes to be paged in and out of the working set.
Like pagefile only faster ofc as it's paging from RAM not the HDD. It's all just storage anyway.
Working set still same 4GB however so the extra RAM was mainly used for file caching on servers.

2: Microsoft's name for a "32bit OS" which can magically handle over 4GB total is PAE.
This concept is smoke and mirrors anyway:
An OS is essentially many programs running at once inside a user friendly GUI. Programs are made up of process, then threads which ofc run on a CPU cores.
So how does an OS determine a memory limit for the hardware which hosts it. Because big daddy kernel (basically a gateway) limits processes from asking for more space. ...
like Oliver Twist CPU by way of.
The number of processes which can run on the hardware in truth is up to the hardware. It's the kernel which (artificially to an extent) prevents any more addresses being handed to the CPU for staorage.. S

So with Windows PAE a more accurate depiction would be a restriction is lifted, nothing is extended or added.

PAE for processors isn't needed by AMD64, due to a couple of fundamental architecture difference between AMD64 and IA32/64.
One being AMD64 MCT don't need linear addresses when translating between virtual and physical addresses.

From CPU to RAM 64 address lines were available, clearly more than what a Windows 32bit OS can handle. There are more address lines also leading from the CPU to chipset NB.
These are the internal registers, these lines are how pages get swapped from the pagefile to RAM,among other things.
IA32 needs the internal registers when running 64bit OS because IA32 (not IA32e) can only handle 64bit processes if the pagefile is enabled.
Without a PF total address space period for IA32 is 4GB.

Which brings us to the :"Driver Incompatibly" issue MS would have us consumers believe.

So IA-32 dependant on model get 32physical lines going to the Northbridge, 32 going to Southbridge
Intel-64 had 32/64. Xeon had 64/64. correct me if I'm wrong as I'm working from memory.


And please don't insult my intelligence by actually suggesting I read a Misplaced Pages article on VM or anything recommend

In AMD's case Windows has to extend its own addresses beyond 4GB in order to use all address space available to the CPU
The onus is on an OS to be able to use all the address space available to the CPU not the other way around. Hardware doesn't run on an Operating System the Operating System runs on the hardware. Tell me again how PAE works for AMD64?

Anyway Intel was the opposite, and tbh the "Physical" when it comes to Physical Address Space is a misgnoner.
Windows doesn't control the AMD Northbridge, The CPU does, and it can address as much memory as it was designed for. The OS can only limit it's own addressing.



And re: my talk, how bout u let Jeh answer for himself.

PAE isn't actually relevant after XP anyway since MS use licensing checks.

Which is another topic in in itself. How can PAE "add" something that was always there? XPSP1 on AMD64 8GB was accessable no problem, XPSP2 comes along which prevented the OS from using addresses over 4GB. Not the CPU's fault.

Sounds more like Physical Address Reduction, not Extension. Somebody please remind me.....the difference between XP and Server 2003 is.....what? The cost?



@Guy Harris, some of what you said doesn't make sense.

:Furthermore, if you don't have paging virtual memory enabled, PAE doesn't even exist - PAE involves a modified form of the page table, with larger page table entries capable of providing more bits of physical address, expanding the physical addresses generated for virtual addresses from 32 bits to 36 bits.

No kidding that's why it doesn't have any effect on AMD64.
Why not just say "PAE enables paging on the CPU? Or something to that effect..

And "'''paging virtual memory'''"? What is "paging virtual memory"? I know of pagefile, page table, pages, virtual memory, even tables.
But "paging virtual memory" is new one to me. Any links to technical documentation explaining the concept of "paging virtual memory" - much appreciated.
I love learning new tech.

"PAE involves a modified form of the page table?" My 7 year old niece could quote that line back to me, right after reading wikipedia.
How about describing the page table modification in detail? Let me: PAE doesn't add a page table it adds a page table directory pointer which points to the page table. Simple.
Any other obvious info I need to be made aware of as you assert your superior knowledge?

As above 36bit addressing was needed because Intel hardware generally had 32bits external for RAM access, less 4bits was for the page table directory pointer.
Possibly why x87 compilers limited 32bit processes to ~3.6GB or 3.7GB.
AMD don't need or use or know about PAE because all their page tables are stored in RAM which is entirely and directly accessible by the CPU without paging.


Attempting to fluster users/editors with jibberish and nonsensical terms.... is pretty unethical, who wins nobody?

Lastly, Microsoft are software developers, not ASIC manufactures. MS work very closely with Intel.
An expertise in one does not mean expertise in the other. Just some food for thought.

@Jeh, thanks, this is a great example of why I wasn't interested in going to talk with you.
Had a reasonable discussion been on the cards yes by all means, I would look forward to it. Tbh I'm not even sure if some of the more nonsensical comments posted here were intended or not.. But I assume good faith.



And no, I didn't use quotes, possibly there may be duplicate comments too..I didn't check.] (]) 10:55, 13 April 2017 (UTC)
:{{ping|PastieFace}} And your comment here ''still'' indicates that you don't understand this topic. An ] is ''not'' just "essentially many programs running at once inside a user friendly GUI." An operating system has to ''schedule'' those programs while ''providing isolation''. And most programs and server operating systems don't even expose a GUI to the user at all. Your comment that "There is PAE designed by and implemented by Intel on architecture which allows processes to be paged in and out of the working set." is also incorrect, because physical pages are by definition in RAM (where else? The CPU cache has nothing to do with this concept). Also "Because big daddy kernel (basically a gateway) limits processes from asking for more space." is incorrect because the whole story of memory management is ]. If a process only speaks 32-bit addresses it literally ''can't'' ask for more than 4 GB of memory, period. That's not a restriction imposed by the OS, unless the OS decides to be stricter for any reason. "PAE isn't actually relevant after XP anyway since MS use licensing checks. " - again, incorrect: PAE is relevant to 32-bit versions of ] (and most other 32-bit versions of Windows, for that matter), which postdates Windows XP. "Which brings us to the 'Driver Incompatibly' issue MS would have us consumers believe." - let me ask you, do ] drivers have the luxury of virtual memory?
:"And please don't insult my intelligence by actually suggesting I read a Misplaced Pages article on VM or anything recommend" - if you tell us blatantly incorrect things such as the notion that PAE is ''only'' a Windows on Intel thing, what else am I supposed to infer? And "As above 36bit addressing was needed because Intel hardware generally had 32bits external for RAM access, less 4bits was for the page table directory pointer." is incorrect. That's not how a ''3-level'' page table works. "AMD don't need or use or know about PAE because all their page tables are stored in RAM which is entirely and directly accessible by the CPU without paging." Uhm no - at least in recent versions of AMD processors, there are still hardware page tables, and even nested page tables for virtualization (]).
:None of this is directly relevant to the edit in question, anyways. The fact is, your addition said ''nothing'' new whatsoever on the subject of PAE and was a direct copy/paste from the manual, and ] has therefore been against it, so it will stay out of the article.--] ] 15:31, 13 April 2017 (UTC)

@Guy Harris;
I'm retracting my reply to your comment "paging virtual memory".
After thinking it over I agree with you, technically you're right since PAE essentally just allows paging. I always looked at it as paging from where didn't matter ver.
The terminology tripped me up as to me paging is paging no matter where from or to.
I realised also your comment nullifies any argument over whether IA32 can access over 4GB of RAM. Also it illustrates how the "P" in PAE is quite misleading. :)] (]) 17:48, 13 April 2017 (UTC)

@Aaron, yes after rereading I realised a couple of minor comments made were not 100% accurate. One was obviously stating the pagefile allows 64bit processes to run. :P
Also, I realise PAE is not new but in the context of the article it is ambiguous to imply x86/64 processors in general make use of PAE.
Just as to state 32bit (physical bits) architecture in general can support as much RAM as 40bit or more. This POV comes across to me as very biased toward Intel and snubbing AMD.
I suggest the above mentioned topics be broken down by vendor and micro-architecture to maintain neutrality. Thoughts? ] (]) 18:16, 13 April 2017 (UTC)
:{{ping|PastieFace}} Please remember to indent your comments by prefixing each new line break with the appropriate number of colons in the markup.
:And also, PAE itself is not the enabler of paging, which predates PAE by quite a long time. Rather, it allows a greater total size of the set of physical pages to take advantage of more memory.
:I opened this conversation to discuss the edit you made. Do you still stand by that edit?--] ] 18:29, 13 April 2017 (UTC)

:{{ping|PastieFace}} Yes, PAE is just a change to the way paging works at the ''hardware'' level. It extends the size of page table entries to 64 bits, allowing them to have more bits of physical address. Without it, an IA-32 processor, whether from Intel (] onwards) or AMD (] onwards) can generate a 32-bit physical address, so it can only handle 4GB of physical memory; with it, an IA-32 processor, whether from Intel (] onwards) or AMD (] onwards), can generate a 36-bit physical address, so it can handle up to 64GB of physical memory (''if'' the chipset and motherboard can). Both without and with PAE, the logical addresses that are mapped to physical addresses are 32-bits long. IA-32 processors with PAE ''cannot'' support more than 2^36 bits of physical address; it can't support 2^40 bits of physical address, whether the processor is from Intel or AMD.

:As for ], whether from AMD (] onwards - AMD originally called it x86-64, but changed it to AMD64) or Intel (64-bit versions of the ] onwards - Intel calls it EM64T, IA-32e, or Intel64, depending on the phase of the moon), it uses 64-bit page table entries, just as IA-32 with PAE does, but the page map has more levels, so it can map a 48-bit address to a physical address. The physical address size varies from processor to processor, but it's at least 40 bits. Those aren't IA-32 processors, those are x86-64 processors, so they're not limited to 32 bits in linear addresses and are not limited to 36 bits in physical addresses.

:So there's not much "AMD vs. Intel" here; both Intel and AMD implement paging since the 80386/Am386, both Intel and AMD implement PAE since the Pentium Pro/Athlon, and both AMD and Intel implement x86-64 since the Opteron/later Pentium 4.

:And the only way the microarchitecture makes a difference is the number of physical addresses that a ''64-bit'' microarchitecture, implementing x86-64, provides. All 32-bit microarchitectures that provided PAE provided 36 bits of physical address.

:So there's no neutrality issue, and there's no need to break anything down by vendor or microarchitecture. The only distinction to be drawn is between IA-32 with PAE and x86-64, and this page primarily covers IA-32 with PAE, as it should. PAE isn't an option in x86-64 - you ''have'' to turn PAE on to do paging in long mode - but the page map is different in that mode (one more level, to handle the longer virtual addresses), and ''that'' is described in ]. ] (]) 18:52, 13 April 2017 (UTC)

@Jasper: :"And also, PAE itself is not the enabler of paging, which predates PAE by quite a long time"

In reply to the first half of your sentence PAE is the method by which processors which use PAE page out.
The 2nd half is not even relevant to anything I said because I never discussed where PAE originated from nor care for that matter. However if you're going to tutor me on PSE don't bother. It's not even important.

Re: edits which part in particular are you referring to? Regardless if I stand by it you will know because it will be reverted, no need to worry.
Besides the talk page is here for these discussions.
Tbh I haven't even gone through the revisions since the other day as been too busy. I hardly have time to reply now...] (]) 18:49, 13 April 2017 (UTC)

:No, PAE is the mechanism by which processors that use PAE map 32-bit linear addresses to 36-bit physical addresses, rather than just to 32-bit physical addresses, as they have to do without PAE. Paging in and out can be done the same both ways, even if Microsoft chose to handle physical memory beyond 4GB differently. ] (]) 18:58, 13 April 2017 (UTC)
:{{ping|PastieFace}} To say that PAE "enables" paging is to imply that paging is not possible without PAE, which is obviously not true. I assume you understand what Guy Harris means by paging virtual memory because paging is not the only way to do virtual memory (although it is considered the best we have right now).
:As for the edit in question I'm referring to . Since as you know by now, reverting excessively (edit warring) is no way to indicate objections to an edit, I felt it necessary to ask you here.--] ] 19:05, 13 April 2017 (UTC)

@Guy. after going over some of your discussion history in other articles in which you take Intel published whitepapers completely out of context, I retract my apology and retraction.
There is no doubt in my mind of a COI neutral POV issues here, and in other articles.

@Jasper, your line of questioning clearly isn't leading anywhere constructive so unless you want to chit chat I'm not interested in discussing anything further.
The edit was and is currently reverted so if you continue to badger/attempt to bully me with veiled threats I'll happily take it to the admins.

Also, I see Aaron Jangewean was trolled into a ban by a couple of you. Not hard to see what's going on after looking at a years worth of discussion.
Think back to 2009, what happened with M$ and Misplaced Pages?


It should be made clear the only IA-32 processor which supported Physical Address Extension as defined by Intel was Xeon. PAE requires BOTH 36 address registers AND 36bit data bus for RAM.
I'm not going let myself be goaded into a block/ban whatever at the moment... I'll be in background though... Stop harassing me.] (]) 23:53, 13 April 2017 (UTC)
:{{ping|PastieFace}} ]. I was merely wondering if you were still interested in keeping that edit. Since it appears that you're not, we don't need to continue this conversation; Guy Harris' comments elsewhere are ]. On the other hand, if you accuse me of bullying or harassing without evidence again, I'm not going to be okay with it, because that's not what I'm doing.
:And in any case, make sure you read ] before you talk about neutrality. I'm not affiliated with Intel or Microsoft so I have no COI. Again, since the reason why I opened this conversation no longer applies, there's no need to continue this unless you have something concrete to suggest.--] ] 00:10, 14 April 2017 (UTC)
:: {{ping|PastieFace}} One: I have no idea what you refer to by ''"2009, what happened with M$ and Misplaced Pages? "'' I don't know, what did happen? ] (]) 01:06, 14 April 2017 (UTC)
:: Two: Having your erroneous claims responded to with well-referenced facts is not "biased", "slanted", or "harassment". And it will likely continue. ] (]) 01:11, 14 April 2017 (UTC)


All IA-32 processors had at most a 32bit data bus. 36 address registers only allows paging - it is not PAE support.
== Ambiguous ==


Only Xeon had 36bits for RAM. Xeon supported 8GB RAM total. The 8GB was split into 2x 4GB memory banks accessed one bank at a time. The 32bit + 4bit bus allowed a segment selector.
{{cquote|The NX bit feature is also available when these CPUs are using PAE in protected mode or compatibility mode.}}
(Xeon was technically a 36bit CPU).


] (]) 23:25, 10 May 2020 (UTC)
The above words is written by someone who I do not want to mention at all, but this expression is ambiguous and even wrong in the Lexicon. Feature could not be described with words such as "available" or "unavailable", because they are present or not, one in two! They could never hide or come out suddenly make you frightened. The NX bit feature comes with the processor(s), it would function or not, but the precedencies are they are present. This function could be enabled or disabled under firmware, such as BIOS or (U)EFI. But the only entry for it is enabling PAE, because it is an extensional feature of PAE, and built on PAE.


:No, as that's rubbish. Where's the definition of that per Intel? The article currently has it right ] - the chipset and motherboard etc have to also support 36 bit, which I know myself certainly some non-Xeons did. <span class="vcard"><span class="fn">]</span>; ]</span> 22:09, 1 September 2020 (UTC)
If PAE is a feature of CPU, not matter on the ISA or system level, the processor could never use it, because it is a feature! The subject uses PAE is the programmes, the firmware, Operating System and so many other things, but not the processor!


== First Linux kernel to support PAE ==
Real Mode, Protected Mode and Long Mode(or IA-32e mode) build up the fundamental modes of x86-64 processors. Real Mode, Protected Mode and Virtual x86 Mode are also treated as Legacy Mode; but Compatibility Mode and 64-bit are two sub-modes of Long Mode (or IA-32e mode). So Protected Mode and Compatibility Modes sit on different levels, could not be talked about together. And PAE could only work on Protected Mode and Virtual x86 Mode. The paging system after processor entering into Long Mode is not called PAE, or an enhanced version of PAE, it is just the 64-bit mode paging.


The section says 2.3.23 but under the old scheme odd numbers were development kernels (2.2 series was the release, 2.3 was concurrent and the development space for what would ship as 2.4). Would probably make sense to also mention which kernel was the first to ship with PAE, since no released distro would use a development kernel. --] (]) 03:44, 1 May 2022 (UTC)
This sentence is made up with lots of mistakes from the grammars, from the lexicon... towards to the real thing which it described.

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PAE Xeon only

It should be made clear the only IA-32 processor which supported Physical Address Extension as defined by Intel was Xeon. PAE requires BOTH 36 address registers AND 36bit data bus for RAM.

All IA-32 processors had at most a 32bit data bus. 36 address registers only allows paging - it is not PAE support.

Only Xeon had 36bits for RAM. Xeon supported 8GB RAM total. The 8GB was split into 2x 4GB memory banks accessed one bank at a time. The 32bit + 4bit bus allowed a segment selector. (Xeon was technically a 36bit CPU).

Onzite. (talk) 23:25, 10 May 2020 (UTC)

No, as that's rubbish. Where's the definition of that per Intel? The article currently has it right Physical Address Extension#Hardware support - the chipset and motherboard etc have to also support 36 bit, which I know myself certainly some non-Xeons did. Widefox; talk 22:09, 1 September 2020 (UTC)

First Linux kernel to support PAE

The section says 2.3.23 but under the old scheme odd numbers were development kernels (2.2 series was the release, 2.3 was concurrent and the development space for what would ship as 2.4). Would probably make sense to also mention which kernel was the first to ship with PAE, since no released distro would use a development kernel. --97.115.191.42 (talk) 03:44, 1 May 2022 (UTC)

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