How is physical memory recognized by a 32-bit OS running on 64-bit hardware?

Caviar — Mon, 14 May 2007 15:30:44 -0800

How is physical memory recognized by a 32-bit OS running on 64-bit hardware? (This was originally a comment on an older thread, but it went unanswered, so I'm asking a fresh question.)

Can someone explain how the murky 4GB barrier works in 32-bit Windows? To be more clear - currently, on a 32-bit CPU with a 32-bit OS, if you put 4GB of RAM in the machine, it doesn't recognize more than about 3.5GB because some is reserved by the PCI bus, and of that RAM, you can only allocate 2GB to any given process because the kernel reserves a bunch. What about on a 64-bit CPU (still with 32-bit Windows)? If you put 8GB into the machine, do you get 3.5GB for the kernel, 512M for the PCI bus, and a separately addressable 4GB physical RAM that can be allocated to a process? What happens if you have exactly 4GB of RAM? Does it behave just like a 32-bit OS on a 32-bit CPU?

64-bit n00b, doesn't want to be a b00b.

bartleby — Thu, 03 May 2007 09:48:32 -0800

Getting new laptop with x64 processor...should I get 32-bit Vista, or 64-bit? Does it matter? How about 64-bit XP? New laptop purchase candidate has AMDx64 processor.
But my only knowledge of 64-bit computing is that it seems to provoke headaches.

I’ve gone through the 64-bit threads here, but many of them are a year or more old, so I don’t know if the situation has improved.. I wouldn’t bother asking, but considering that my last 3 computer purchases were basically free (recycling –No! Upgrading!- older machines to Linux), I’m fretting over spending $$$ on the wrong thing.

It’s just a ‘very-portable’ home/biz laptop that’s maxed out at 2gb RAM. So no bonuses for 64-bit’s higher RAM ceiling. Not for gaming, no overclocked CAD/video editing workstation, etc. Simply wanted a small notebook with Vista. It just so happened that the form factor I liked comes with a 64-bit processor.

Okay, you early adopters who might have gone through this already, a couple questions:

1) This will be my first Vista machine AND my first x64 processor. Will I have more or less problems with running a 64-bit OS on a 64 bit processor than I would running 32-bit version of the same OS on the same machine? Would I even notice any gain from x64, given that I’m only on 2gb RAM anyway? Does the x86 emulation or whatever lets it run in 32-bit mode suck and slow things down? Trying to pick which flavor of Vista will run smoother…

2) I ask because I would like to get Vista Ultimate, but the OEM for this only offers it in 64-bit, even though their Premium & Business offerings are 32-bit. I need to join a domain, so it’s Business at the least; but I am also interested in the Media Center stuff in Ultimate. If I’m stuck with a crap 64-bit Ultimate or a functioning 32-bit Business, I’m going to have to go with Business. No difference? Ultimate. Who owns either or both and can tell me about it?

3) Sort of eliminating the above question; if anyone has an OEM Vista Ultimate DVD: did it come with both the 32-bit and 64-bit versions on it, like I hear that the retail version does? If so, then we’re done: I’ll have the option to try both. for what works better. If not, repeat question 1.

4) I’m going to set up this machine with an XP partition to boot from for the times when Vista isn’t my friend. And I just so happen to have an unused XP Pro 64bit install package lying around doing nothing but being shrinkwrapped & legit. (I ended up with this as a gift from someone who tried XPx64 on a few machines in 2005 and gave up in tears.) “Why not save a couple hundred dollars and use it instead of buying XP again”, I say to myself “- they must have improved it since it came out”. But maybe it still sucks? Is XP x64 going to give me a whole other set of headaches, making it worth going out and buying a retail XP 32-bit copy for my dual-booting to safety needs? Expensive!

5) Bonus Question: Who was Casper the Ghost before he died?

Thanks for all your help, everybuggy.

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How is physical memory recognized by a 32-bit OS running on 64-bit hardware?

64-bit n00b, doesn't want to be a b00b.