IT IS A CPU LIMITATION, YOU DOLT!

[strredwolf]

A particular "software analyst" claims that the 4 gig RAM limitation in 32-bits is a joke, and says it's a Vista licensing scam from Microsoft.  http://www.geoffchappell.com/viewer.htm?doc=notes/windows/license/memory.htm for the full article.

Let me call bull on this one.

First, and most simple reason:  Some CPU's have 32 bit wide address spaces.  The newest one to have this is the Intel Atom (the one geared for netbooks).  If the address space is set for 32 bits, that means it can only address 2^32 (that's 2 to the 32nd power) bytes of RAM.  2^32 is 4 gig (not 4 billion bytes, that's the base 10 version).   To get even more RAM address space, you must have a 64-bit processor that can address more space... and not all of them will do it.  Some Core 2 Duo's are stuck in 32-bit hell, but AMD's Athlon 64's, 64 X2's, and Phenoms are all 64-bit.

Now, to get even more technical, because there's a few "gotchas".

Second:  Because a 32-bit CPU can only address 4 gigs of space, and a video card (like the Nvidia Geforce cards) has up to a gig of RAM for itself, you're going to loose whatever main memory you have if you max the RAM for the CPU out to 4 gig.

Example:  Nvidia Geforce 9800 on a WinXP system, having 4 gigs of RAM and a 1/2 gig on the video card.  XP will report at most 3.5 gigs because the video card has to be fully seen.

You don't have that limitation in 64-bit mode.

Third:  There is a way around it, but it's crude and comes from the 16-bit days of the IBM XT.   Back then, it was called LIM EMS (Logitech/Intel/Microsoft Epanded Memory Specification), which swapped 64K chunks of RAM supplied on an expansion board in and out of a reserved area of the 1 Meg address space the old Intel 8088 CPU has. 

Now, in 32-bit land, a similar technology is called PAE.  And it's only useful for swap, because it's slower than accessing the RAM directly (in 64-bit mode) but faster than smacking it onto the disk.

Now who thought up of PAE (Physical Address Extention)?  Intel, back in the Pentium Pro days.  The same guys who invented LIM EMS!

Forth:  Vista's a joke by itself anyway.  Wait until October and get a copy of Windows 7, or go with a copy of Ubuntu 64-bit.

Comments

[kazriko.livejournal.com]

Good post. The last thing we want to do is return to the bad old days of segmented memory. Flat memory model 32-bit was the best thing to happen to computer science in ages. I remember the pain of setting up overlays in Pascal so they would page in and out of the 64k pages, and how irritating it was to maintain even in that simplified environment (and it made C a nightmare with 5 different memory models to pick from...)

If only 64 bit windows didn't SUCK so much. There's just so many incompatibilities with 32 bit and 16 bit software on it, and that means many of the programs I use for my job fail to work on my home Vista 64 bit system.

[strredwolf.livejournal.com]

It's not all that better in Linux 64-bit. There's still some code that uses 32-bit integers and when int goes 64-bit, all hell breaks loose. And I hear ya with C on those 8088 -- I was using QuickC to port some AppleII programs over and I had to choose which pointers I needed because of the nice 20-bit wide address bus that was segmented.

[kazriko.livejournal.com]

Yeah, int going 64 bit will be an adventure on an order higher than the Y2K fiasco. But we do have around 20 years to deal with that particular problem.