pae kernel

[Was_Just19]

OK, got my problem sorted .....  I had corrupted the device.map file with some other things I was doing. So having corrected the file and reinstalled the two kernels, which had correctly installed but had not been added to the menu.lst due to the above problem, here are the results .......

kernel-2.6.38.2-pclos1.bfs

Available RAM:  3.22GiB

Free shows:   3372676 Total

***

kernel-2.6.38.2-pclos1.pae.bfs

Available RAM:  3.17GiB

Free shows:   3319364 Total

*************************

So on this particular machine the pae kernel provides less memory for use, out of the 4GB installed.
The difference does not seem as large as it was the last time I checked it.


regards.

[Old-Polack]

With the .bfs kernel I get something like 3.6 GB reported, while the .pae gives me this;

[root@fatman ~]# free

Code: [Select]

             total       used       free     shared    buffers     cached
Mem:       4073260    3811056     262204          0     225548    2484312
-/+ buffers/cache:    1101196    2972064
Swap:     14105060       1172   14103888

I can't reboot right now to check the exact amount reported with the .bfs kernel, but the difference has been consistent between what any of the other kernels show and what any of the .pae kernels show.

[root@fatman ~]# uname -r
2.6.38.1-pclos2.pae

[Jaws]

With the new 2.6.38.2 pae.bfs kernel and a recent (2 hours ago) reboot.

Code: [Select]

             total       used       free     shared    buffers     cached
Mem:       4104752     869108    3235644          0      37292     394932
-/+ buffers/cache:     436884    3667868
Swap:      4088536          0    4088536

[T6]

"Are you sure that the 4GB ram limit doesn't include video ram? It does on windows computers and I assume they would both have the same 32-bit cap. Addressing limits *waves hands*"

i never heard this on windows and linux

read this from microsoft, on the lower part there is more interesting comments

http://msdn.microsoft.com/en-us/library/aa366778(v=vs.85).aspx

more

http://www.graphicsvideocard.com/does-xp-3-5gb-mem-limit-affect-video-card-memory

as you see it is a little confusing but afik there is no such limit

you can use the ram on the video card as system ram but is complicated and prone to crash

[FritoBandito]

hmm this is confusing

but i did just try them all and:

kernel	a64	pae.bfs	bfs
mem detected	3.2gb	3.91gb	3.22
mem free	2.42gb	3.15gb	2.34gb
mem used	0.78gb	0.76gb	0.88gb

i dont know which is the snappiest but the pae gives the most ram for me and uses the least.
These were all 5 minutes after boot with nothing running.


I thought (not sure now) that the video memory changes in windows because i've stuck in cards with different memory sizes and i see it change accordingly... but that was on older cards... supposedly this is no longer the case... NEAT!

[Old-Polack]

Just installed the new .pae.bfs kernel, and it sees more memory than the last .pae kernel.

[root@fatman ~]# uname -r
2.6.38.2-pclos1.pae.bfs

[root@fatman ~]# free

Code: [Select]

            total       used       free     shared    buffers     cached
Mem:       4098964    1702552    2396412          0      61736     677656
-/+ buffers/cache:     963160    3135804
Swap:     14105060          0   14105060

[T6]

what video card do you have?

integrated video card takes a part from the ram to use it for the video card, this ram won't be reported as system ram on some machines, especially on intel machines using intel card

[AS]

I have installed 4 kernels:

2.6.38.2-pclos1
Mem:       3097480     

2.6.38.2-pclos1.bfs
Mem:       3112948

2.6.38.2-pclos1.pae
Mem:       4074304

2.6.38.2-pclos1.pae.bfs
Mem:       4100020

AS

[FritoBandito]

negatory, they were all discrete cards but I suppose this is no longer the case

[AS]

Are you sure that the 4GB ram limit doesn't include video ram? It does on windows computers and I assume they would both have the same 32-bit cap. Addressing limits *waves hands*

No, in fact I was wrong. I made a little search around this things, here the results:
32 bit OSes, without using PAE, can address a maximum of 4 Gb RAM.
video card memory must be mapped into the addressable space (and this is done by both Windows and Linux).
-if you have only 2 Gb of system RAM, it is  possible to map the 512 Mb video ram inside the 4 Gb address space
-if you have 4 Gb of system RAM, and because you need to map the video RAM (and all others IO Memory) into the 4 Gb address space,
part of the system RAM  will be unusable because of overlapping of all device IO Memory, not only the video card.

if you use a PAE Kernel, the addressable memory is large as 64 Gb, therefore the kernel can easily map the 4 Gb System RAM + approx 800 Mb of device IO memory,
on Linux you can see the mapped IO memory in /proc/iomem.

addtional info here(include some info on hardware limits):
http://duartes.org/gustavo/blog/post/motherboard-chipsets-memory-map

windows info here (guess what ? 32bit Win do have PAE, but can't really use PAE):
http://support.microsoft.com/kb/929605

AS

[Was_Just19]

windows info here (guess what ? 32bit Win do have PAE, but can't really use PAE):

I didn't read the link you provided, but some 32 bit versions of Windows were available with a pae kernel ...  mostly servers I believe.

I recall reading that the pae kernel was available in all Win distributions, but was not accessible/usable unless the correct licence was purchased.

[T6]

"video card memory must be mapped into the addressable space (and this is done by both Windows and Linux)"

you write this but i found info on both links i posted saying that this is wrong

[AS]

windows info here (guess what ? 32bit Win do have PAE, but can't really use PAE):

I didn't read the link you provided, but some 32 bit versions of Windows were available with a pae kernel ...  mostly servers I believe.

I recall reading that the pae kernel was available in all Win distributions, but was not accessible/usable unless the correct licence was purchased.

Not exactly, windows 32 bit can eventually boot using a /PAE option:
http://msdn.microsoft.com/en-us/library/aa366796%28v=vs.85%29.aspx

The fact is that booting XP using the PAE option would require that all drivers should be ready for PAE which look quite not true,
so using M$ jaargon, they say the system become "unstable".  Linux doesn't have the driver problems, because all drivers are recompiled with it's own kernel.
M$ itself discourage the use of PAE switch:

The reduction in available system memory depends on the devices that are installed in the computer. However, to avoid potential driver compatibility issues, the 32-bit versions of Windows Vista limit the total available memory to 3.12 GB. See the "More information" section for information about potential driver compatibility issues.

http://support.microsoft.com/kb/929605

About licenses ... great story here:
http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm

another related link:
http://msdn.microsoft.com/en-us/library/aa366778%28v=vs.85%29.aspx

AS

[AS]

"video card memory must be mapped into the addressable space (and this is done by both Windows and Linux)"

you write this but i found info on both links i posted saying that this is wrong

To say the truth, I have found all and the contrary of all, not a simple argument this one.

"Are you sure that the 4GB ram limit doesn't include video ram? It does on windows computers and I assume they would both have the same 32-bit cap. Addressing limits *waves hands*"

i never heard this on windows and linux

read this from microsoft, on the lower part there is more interesting comments

http://msdn.microsoft.com/en-us/library/aa366778(v=vs.85).aspx

from the above link:

Therefore, if the system has 4GB of RAM, some of it is either disabled or is remapped above 4GB by the BIOS

I read this as "disabled" when addressing limit is 4 Gb, "remapped" when addressing limit is above 4 Gb, PAE.

more

http://www.graphicsvideocard.com/does-xp-3-5gb-mem-limit-affect-video-card-memory

as you see it is a little confusing but afik there is no such limit

you can use the ram on the video card as system ram but is complicated and prone to crash

I agree with this second link, but from a practical point of view some amount of system memory must be used for viideo card driver,
read this from nvidia:
http://us.download.nvidia.com/XFree86/Linux-x86_64/96.43.19/README/appendix-l.html

The NVIDIA kernel module requires portions of the kernel's virtual address space for each GPU and for certain memory allocations. If no more than 128MB are available to the kernel and device drivers at boot time, the NVIDIA kernel module may be unable to initialize all GPUs, or fail memory allocations

The above however contribute to decrease the available system RAM ...

AS

[Was_Just19]

windows info here (guess what ? 32bit Win do have PAE, but can't really use PAE):

I didn't read the link you provided, but some 32 bit versions of Windows were available with a pae kernel ...  mostly servers I believe.

I recall reading that the pae kernel was available in all Win distributions, but was not accessible/usable unless the correct licence was purchased.

Not exactly, windows 32 bit can eventually boot using a /PAE option:
http://msdn.microsoft.com/en-us/library/aa366796%28v=vs.85%29.aspx

OK, a pae option according to that link but also from your link
http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm

If you have physical memory above 4GB and wonder how it can be that the PAE kernel does not use that memory, the answer is licensing. The 32-bit code for using memory above 4GB is present in Windows Vista as Microsoft supplies it, but Microsoft prepares license values in the registry so that this code never gets to work with any physical addresses above 4GB.

In other words Win users could have been using more than 4GB except that MS limited the use by licencing.

Of course there is no surprise there .....