Not to be overly simple, but can't you just open task manager and start opening a bunch of memory hungry apps and see if total utilized physical memory is more than 4GB? Seems like that would be pretty cut and dried :)
I only have 4 GB in my top 2 boxes or I would test the theory... lopaka ________________________________ From: Greg Sevart <ad...@xfury.net> To: hardware@hardwaregroup.com Sent: Tue, August 3, 2010 2:42:59 PM Subject: Re: [H] new system build suggestions or upgrade I'm still quite confident that you're mistaken. Client Microsoft operating systems and Server SKUs less than Enterprise simply will not use any more than 4GB. They're technically capable of leveraging PAE to extend memory usage, but they don't. They will use PAE to support DEP (and NUMA, apparently), but that's it. Windows 7 and fully patched versions of Vista will, however, _report_ all installed system memory, but it will not use one byte more than 4GB. I'd be happy to eat my words if you can point out a Microsoft-published document that definitively indicates that I'm incorrect, but I don't believe that is the case. This document also outlines memory limits of 32-bit Windows versions that is marked current as of May 2010: http://support.microsoft.com/kb/2267427 Even if I am somehow mistaken and it is somehow possible to use PAE to use more than 4GB of memory under a MS Client OS edition, that still doesn't change the fact that each 32-bit process still has a maximum of a 4GB VAS. PAE and 4GT ("/3GB switch") don't change that. The application must then use AWE (Address Windowing Extensions) to make use of any memory beyond that--and the list of apps that use the AWE API is very small. The only one that I know of offhand that does is Microsoft SQL Server. Greg > -----Original Message----- > From: hardware-boun...@hardwaregroup.com [mailto:hardware- > boun...@hardwaregroup.com] On Behalf Of Soren > Sent: Tuesday, August 03, 2010 2:54 PM > To: hardware@hardwaregroup.com > Subject: Re: [H] new system build suggestions or upgrade > > Heh... nice writeup, Greg, but not completely updated, if I humbly may say > so. > > If one look at the MS support sites about this question, one will get as many > different and contradicting explanations on the subject, as there are support > numbers (Qxyz). Beats the crap out of most techs that I know. > > However, I have built a large number of AV systems, and quite a number of > those are with more than 4GB RAM, even up to 32GB. They all use the > installed RAM without any problems, so I guess that at least *some* of MS's > support sites are right, when some obviously aren't. > > There is no "trickery" because the processor is not limited to 32 bits of > physical address in PAE mode. PAE mode adds a third level of page table > lookup and changes the page table entries (PTEs) from 4 bytes wide to 8 > bytes wide. This gives more room for bits of physical page address, or "page > frame number." In the first CPUs to implement PAE only four more bits were > implemented, for a total of 24, or 36 bits of physical address. Thereby > allowing 64 GB of ram to be directly addressed. No "trickery" is involved. It's > the same address translation the MMU has been doing all along; the format > of the lookup tables (page tables) is just changed. > > As you may see, this is not as much an O/S question, as it's a CPU question. > Nowadays, no problems when using a high grade processor. > > This site pretty much nails it: > > geoffchappell.com/notes/toc.htm > > BTW, one of the finer benefits from using a large amount of RAM, is that the > swap file can be allocated to RAM, which makes makes the system very > responsive. This allocation usually takes place from top>down, depending on > the method used (separate proggie, or just a .reg file). > > ./ > > Greg Sevart wrote: > > Umm....not quite. > > > > While it is technically possible to use more than 4GB of memory on a > > 32-bit OS with PAE, Microsoft client operating systems will NOT use > > it. Even the Standard SKUs of their Server operating systems will not > > use PAE--Enterprise or Datacenter is required. (This actually gets > > even more convoluted--these OS editions DO use PAE to implement > > NoExecute memory protection, but will not actually use more than 4GB). > > > > Furthermore, I think you're confusing user mode memory ("apps") with > > kernel memory ("O/S"). By default, 32-bit versions of Windows XP with > > 4GB or more memory installed will split the 4GB into 2GB of user space > > and 2GB of kernel space. The kernel space is reserved for just > > that--the Windows kernel, kernel mode drivers, etc. You can use the > > /3GB switch (4GT) to move this 2/2 split into a 3/1 user/kernel split. > > Absolutely anything over 4GB is not used, and that's true for 32-bit > > versions of Windows XP, Windows Vista, or Windows 7. > > > > You may lose some of the 4GB address space for memory mapped devices, > > such as video cards and other devices. This is why you will frequently > > see a 32-bit system with 4GB of memory only report 2.8-3.8GB. There's > > no requirement that these devices be mapped to actual memory, just > > that they have memory address space--so 64-bit systems with chipsets > > that support it will remap actual installed RAM around the mapped > > devices. This means that on supported systems and 64-bit OS editions, > > you don't lose any memory to memory-mapped hardware devices. > > > > In short: If you're running 32-bit versions of Windows XP, Windows > > Vista, Windows 7, or Windows Server 2003/2008 Standard Edition, 4GB is > > your limit, and some of that will always be reserved for hardware and > kernel space. > > Period. > > If you're running 64-bit versions of the above, your limit essentially > > depends on whatever MS has licensed for that OS edition. As examples, > > Windows 7 Home Premium is 16GB, Professional is 192GB. Windows Server > > 2008 > > R2 Enterprise is 2TB. More detail, and the limits for all Windows OS > > editions from 2000 to 7/2008 R2, can be found here: > > http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx > > > > Greg > > > >> -----Original Message----- > >> From: hardware-boun...@hardwaregroup.com [mailto:hardware- > >> boun...@hardwaregroup.com] On Behalf Of Soren > >> Sent: Monday, August 02, 2010 8:51 PM > >> To: hardware@hardwaregroup.com > >> Subject: Re: [H] new system build suggestions or upgrade > >> > >> Sorry, not entirely true. There seem to be a common misunderstanding > >> about the O/S allocation of RAM. > >> > >> E.g. WinXP can only allocate 3GB RAM for the O/S, which is often > >> enterpreted as the whole system can only make use of 3GB RAM in total. > >> > >> Actually, XP can only use 3GB RAM for the O/S, any remaining RAM is > >> kindly allocated to applications with a max of 32/64GB for 32/64bit > >> versions of > > the > >> non-server O/S. > >> The rest is plain BS. XP typically uses less than 200MB, btw. > >> > >> The 4GB story is coming from the first release of Vista not reporting > >> the correct amount of installed RAM (e.g. 4GB or 8GB showed up as > >> 3GB), which, quite understandable, lead to a great deal of confusion > >> among guys like > > us. > >> Both Vista32 and W732 run smoothly on +8GB RAM, same with XP. > >> > >> The 64bit thing is driven by the market. > >> > >> Someone wrote: > >>> If you need 4G or more RAM then you're going to need 64 bit > > > > > >
