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4GB shows up as 3.xGB in Win XP (32bit) task manager

H

Helicobacter

Member
I know this is a classic problem and I've researched it quite a bit online.

The argument is made that the OS and the hardware needs some address space.

When I had 2GB, however, all of it was displayed in physical memory!

So, why does it eat away >.8GB when there are 4GB and (almost?) none when there is 2GB?
 
your video card is displacing the ram. it has to map somewhere in the 4gb addressable space. perfectly normal for 32bit xp!
 
Helicobacter said:
I know this is a classic problem and I've researched it quite a bit online.

The argument is made that the OS and the hardware needs some address space.

When I had 2GB, however, all of it was displayed in physical memory!

So, why does it eat away >.8GB when there are 4GB and (almost?) none when there is 2GB?
Click to expand...

What chipset do you have. What is your hardware platform. My Inspiron 1505E only sees 3.3 gb of my memory even with Win 7 64.
 
Same as my 8gb rams show 3.xx in 32bit win 7. Aren't there a software out there will turn displacement to max ram availlable? Since i need to stressing my rams with prim95, don't they stressing 3.xxgb or full 8gb?
 
windows 2003 x86 with AWE mode i run 12gb of ram - sql server uses 8gb and the rest of the o/s (apache/php) runs in the 4gb left for an application server. It even works in vmware 🙂

You can hack XP/VISTA/7 to allow this as well.. but it seems pointless since win7/vista 64bit can just use the ram.

touch screens do this too (nextvision comes to mind) they map a ginormous faux-ram space so if you had 4gb of ram and a 2GB video card and nextvision touch screen you might end up with less than a gig left for o/s on xp 32 bit.

couple of interesting points:
1. OSX 32bit kernel can run > 4gb - the apps which are 64bit (Firefox 4 beta 9) all run fine in 64bit mode on a 32 bit kernel using all the ram. (old macbook's can do 6gb of ram no problem)
2. vmware workstation can run 64bit apps on a 32bit kernel - you can run 64bit ESX 4.0 on a xp 32bit pc - lol

probably some performance loss (very little) - kinda like the old days of highmem and bank swapping in dos. you could have alot of extended/expanded memory but you needed apps that didn't mind TSR'ing in those types of ram space.
 
AWE? Ahh, Address Windowing Extension. Had only encountered PAE, the Physical Address Extension.


32 bits can hold 4 GB addresses. Devices, like graphics, do need some addresses. They probably start using addresses from the end of the range, so use the 3.xx--4GB. When there is less than 3.xx GB of physical RAM, everyone gets addresses. When there is more than 3.xx, the excess gets no address, and only the 0--3.xx is seen.

With the addressing extensions the OS (that supports them) does more bookkeeping and juggles with addition address tables to cope with more addresses. 32-bit applications are still limited on what they can see. Particularly on MS OSes.
 
yah you remember how highmem/expanded ram/extended ram would find the gaps and fill them? you could reorder the TSR's and recurse the combinations to get the most use of that space.

Well in XP they just reserve a ton of memory and said screw looking for tiny page holes. totally boggles my mind.

Also XP can't (like win7) manage the DVMT ram - say if you are doing 2D graphics and text only (AERO) you only need 64meg of VRAM - XP required a bios setting for 64,128,512 etc- if you ran out - oops. Win7 dynamically requests this ram so if you need 64 meg you could push that to the top of the 4gb limit and have your 3.75gb of ram.

iirc my servers get like 3.8gb of ram because between the ILO3 and 32meg of ATI console video - there's not alot of wastage (remember there's bios raid controller bios, chicken scratch ram) up there too.

People buy but 1GB video cards to run "AERO" and surf the web but they don't realize they have just chunked 1gb of usable ram away. and they'll never play games or use the 3D or run 4K video that needs more video ram mapped.

It's really archaic imo. but 64bit takes care of all that mess so nobody decided to tackle the problem. maybe the SUPER SPEED RAM DISK/CACHE folks.

They apparently can take all the holes of ram above that 3.2gb watermark and above 4gb and use it for cache or ram disk 😉
 
Emulex said:
Well in XP they just reserve a ton of memory and said screw looking for tiny page holes. totally boggles my mind.
Click to expand...

I don't think that is possible. The address space between MMIO and 4G is only for MMIO and nothing else.

The ram drive-folks don't address RAM in the MMIO-area. They can only use it, if that ram is remapped above 4G.
 
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