32 bit operating systems and 4 gigs of ram

[captmorgan72]

I have Windows XP home edition that is 32 bits. I have two gigs of ram with two available slots on my motherboard for two more gig chips. I want to throw two more into it but I have read that 32 bit systems can only use two gigs.

I found this thread that looks very promising. What do you guys think?

http://en.kioskea.net/forum/affich-23993-more-then-3gb-ram-on-a-32bit-os

[tommyboy]

I've got a 32 bit o/s(windows xp) and 4gig of physical memory plugged in my main board.
Windows xp sp3 "sees" 3.25- 3.4gig of memory at the moment, depending on which bit of windows you ask (3.25 is via control panel>system, and 3.4 is in task manager>performance).

Now, I cannot remember at the moment exactly why the "missing" memory is missing (something to do with addresses above a certain point being assigned to physical devices like sound/video cards, so it will vary from machine to machine depending on the hardware installed, o/s, mainboard bios, etc,  IRC)

This ramdisk pro or whatever its called might work, but seeing as I've never heard of it before, and I do this stuff for a living, I'd read up on it a bit more before I spent my own, or a customers money.
There are various reputable sites like Tom's Hardware (no relation) that may well offer useful info.

[Panther_Gunn]

Going from what I remember of what I researched on the subject last year, a 32-bit OS has a finite amount of memory addresses available to it (I forget the actual numbers (and don't feel like looking them up/figuring them out), but it's right about 4Gb).  Various system resources *have* to have addresses assigned to them as the system starts up -- video, disk controllers, USB drivers, etc.  After these are all assigned, whatever is left is available to be addressed by RAM.  A typical system can use in the neighborhood of up to 1 Gb of addresses before it's done, leaving around 3 Gb (+/- another couple hundred Mb) for RAM to use.  The hardware will recognize all of the RAM you have installed, but there won't be enough memory addresses available to use all of it.

An easy to understand analogy is phone numbers.  With our standard 7-digit phone numbers, the theoretical limit of phone numbers available is 10,000,000.  When you start taking out numbers that are reserved (no phone numbers starting with "0" means you lose 1,000,000; no phone numbers that start with "911" loses you another 10,000; etc), you end up with a much lower number of useable phone numbers.  The addition of area codes adds another 9,990,000,000 numbers for a total of 10,000,000,000.  A change from 10 million to 10 billion is achieved in a small way (adding three digits) but produces a huge outcome.  This is how a 64-bit OS can handle any amount of RAM we can (currently) throw at it.

As to whether this program will be useful or not is another question.  A RAM disk is essentially creating a virtual hard drive out of "spare" RAM, in the same way that the recent solid-state "hard drives" are done (all of the storage is chip-based as opposed to a magnetic disk).  I first heard about RAM disks back in the 486 days. 

In the end, I don't think it's worth the expenditure to get an exra "drive" of 1 Gb or less, unless you're in a situation where you've already invested in the extra RAM and essentially aren't able to use all of it.  For roughly 3 times that amount of money you can find an external 1 Tb drive.  That's some pretty easy math to do.