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===Memory===
Obviously, the big question about memory is whether 32bit OS can support memory size of 4G and/or above. My machine is recently upgraded to 4x1G DDR2-800, let's see how many was recognized by various OS'es.

==Testbed==
Motherboard: Gigabyte P35-DS3L Bios F6 (Support up to 4G memory)
CPU: Intel C2D 6850
Memory: SuperTalent DDR2-800 CL4 1G x4

==Fedora Core7 64bit==
Needless to say, all 4G is usable.

%%
# free -m
total used free shared buffers cached
Mem: 3968 1008 2960 0 22 450
-/+ buffers/cache: 535 3433
Swap: 1953 0 1953
%%

==Interpreting free==
A side topic to this is how to interpret **free**. Linux uses spare memory to cache I/O operations. Using the above example, 535M is in use by application, 3433M is actually free. This seems to apply to kernel 2.4 only. Ref http://rimuhosting.com/howto/memory.jsp


==Ubuntu 7.10 Desktop 32bit, kernel 2.6.22-14-generic==
Well.. only 3.5G even dmesg says PAE has been enabled & dmidecode sees all 4G of memory modules.

%%
# free -m
total used free shared buffers cached
Mem: 3546 605 2940 0 86 344
-/+ buffers/cache: 174 3371
Swap: 1953 0 1953
%%

==Knoppix 5.1.1 2007-01-04 32bit, kernel 2.6.19==
Same
%%
# free -m
total used free shared buffers cached
Mem: 3549 302 3247 0 8 152
-/+ buffers/cache: 141 3408
Swap: 0 0 0
%%

I even passed the mem=4096m parameter to kernel, in vain
%%
# cat /proc/cmdline
ramdisk_size=100000 ...boring... mem=4096m
%%


==Windows XP sp2 32bit==
Boot.ini
%%
[boot loader]
timeout=15
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn /PAE
C:\CMDCONS\BOOTSECT.DAT="Microsoft Windows Recovery Console" /cmdcons
%%

msinfo32 was able to recognize all 4G of memory
%%
OS Name Microsoft Windows XP Professional
Version 5.1.2600 Service Pack 2 Build 2600
Hardware Abstraction Layer Version = "5.1.2600.2180 (xpsp_sp2_rtm.040803-2158)"
Total Physical Memory 4,096.00 MB
Available Physical Memory 2.71 GB
Total Virtual Memory 2.00 GB
Available Virtual Memory 1.96 GB
%%

BUT no surprises there, even with PAE enabled, Windows is only able to use 3.5G of memory. I guess I'm the lucky one already, some see even less than that.
{{image src="images/xp_4g.png"}}