windows xp maximum supported memory

کسانی که وبلاگ منو دنبال میکنن هیچ لزومی نداره که این پست رو بخوندن
این یه مسئله خاص سخت افزاریه که توش مونده بودم و جوابشو پیدا کردم واسه همین اینجا میزنمش
انگلیسی هم میزنم چون دوس دارم

I had this problem with windows XP maximum supported memory and now I've found the answer. I wanted to share with you.

most people think that the maximum physical ram that can be installed and recognized by XP is 4GB and their wrong! in fact if you have more than 4GB of physical memory and you have windows XP 32bit prfessional, then windows recognize it as 3.12GB or 3.50GB or something like that (between 3GB and 4GB). and windows uses virtual memory (pagefile.sys) to increase the overall memory.

you can change your virtual memory setting here:
control panel -> system -> properties -> advanced -> [in performance box:] settings -> advanced -> change
The virtual memory size will grow automatically due to software needs and grow up to following amount if you've selected the "System managed size" radiobutton:
"4GB - physical memory that you've installed inside your mainboard"
if you've selected the "Custom size" option, it will start from the "initial size" and grow up to the "Maximum size".
suppose that you have a 1GB phyical memory. recommended value for these two sizes are:
initial = 1.5GB (I dont' know why!)
maximum = 4GB - 1GB = 3GB.

also you can change the drive if you don't have enough space on drive C (drive in which windows has been installed). select drive C, select "No paging file", press "Set". then select another drive, select "System managed size" (or "Custom size" and enter desired values) and then press "Set", ok... and restart.

so:
maximum physical memory = between 3GB and 4GB (3GB is recommended).
maximum overall memory = 4GB.

PAE:
check if you see "physical address extension" in your system properties.
control panel -> system -> properties -> general -> [bottom of the page]
PAE means that windows allows the physical memory to be more than 4GB!! BUT IT DOES NOT WORK! shame on xp!
if you don't see that, you can try using PAE to see if it works or not:
Open C:\boot.ini and add /PAE switch to your operating system parameters, save the file, and then restart your computer.
use switches like this:
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP" /noexecute=optin /fastdetect /PAE

suppose that you have 3GB of physical memory installed on your motherboard.
if you try to raise the overall memory more than 4GB it won't let you. because the maximum supported memory for XP is 4GB (physical+virtual).
now, if you run, for example, autocad and open several large files, and monitor the momory activity in task manager, then you'll notice when the memory usage reaches about 1.1GB, your system crashes. but you have at least 3GB of memory!

now this is the trick:
use /3GB switch and then restart.
like this:multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows XP" /noexecute=optin /fastdetect /3GB

now the autocad can use up, up to 2GB of your memory, and do its work perfectly.
/3GB change the allocation ratio between kernel and application, and makes it 1GB to 3GB instead of 2GB to 2GB.
but it WON'T let you have more than 4GB of overall memory.
I suggest you use the "system managed size" for virtual memory. (rightClick on MyComputer -> properties -> advanced -> performance -> settings -> advanced -> change).