Ah. Well, of course 32-bit only supports 4gb.
----------- Brian Sent from my iPhone On 2010-08-03, at 6:33 PM, Thane Sherrington <th...@computerconnectionltd.com> wrote: > At 07:26 PM 03/08/2010, Brian Weeden wrote: >> Um, I just opened a bunch of programs on my Win 7 Ultimate 64bit system with >> 8GB of RAM and it is reporting 4612 MB in use and 3578 free. > > Greg is talking 32 bit. > > T > > >> --------------------------- >> Brian Weeden >> Technical Advisor >> Secure World Foundation <http://www.secureworldfoundation.org> >> +1 (514) 466-2756 Canada >> +1 (202) 683-8534 US >> >> >> On Tue, Aug 3, 2010 at 5:42 PM, Greg Sevart <ad...@xfury.net> wrote: >> >> > 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<http://msdn.microsoft.com/en-us/library/aa366778%28VS.85%29.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 >> > > > >> > > > >> > > > >> > >> > >> > > >
