Pardon me while I mangle this next bit, but as I understand it, ANY 32-bit OS can only address 2 or 3 gigs of RAM. I'm mulling a new workstation with at least 4 gigis of RAM, which certain of my programs will utilize as buffer. So I believe i need a 64-bit OS. Only, Vista is generally reputed to suck, and I'm looking at the nVidia SLI, which doesn't even have drivers out for Vista yet. What other Win OS's have 64-bit mem things going on? XP 64? Win 2003?
I don't care about any aspect of Vista. I need my OS to function as, well, an Operating System. So what are my choices, and do any of them have the non-MSFT characteristic of just working unobtrusively?
Windows XP 32-bit can only access 4GB of ram. The gotcha is that with XP, that includes the PCI address space, etc. This means in reality you'll only get 3GB free if you are lucky, and it is semi-likely that you'll only see 2-2.5GB, even if you have 4GB of physical memory.
I'm running Visa 64-bit "Ultimate" w/MC 12 and 4GB of RAM dual headed with a pair of GeForce 7600 GT SLIs (not running in SLI mode) and an AMD X2 3800+.
I choose it over XP 64 because there is at least hope that you'll have driver support. I'd bet that XP 64 is a total lost cause. My guess is that as far as OS functionality goes, XP 64-bit and Visa 64-bit are probably pretty similar.
It is not without issues or for the faint of heart, but it does work for the most part. Being on the bleeding edge of 64-bit Vista means you need to pick your devices carefully (you may need to change some), choose and install software carefully, and expect issues. The biggest problem at this point is 64-bit driver support which is OK for fairly new devices, but older device support is pretty spotty.
A lot of it depends on what you want to do. Obviously it sounds like you have some concerns/requirements around memory. Start with that need and map it out.
Vista 64-bit is not care free at this point. You can see I had a problem where iTunes DRM content wouldn't play under MC 12 for a while, then with an iTunes update magically started working again. The thing Vista 64-bit has going for it is that people are starting to support it, where most vendors never had XP 64-bit on their roadmap. I expect that it will *slowly* get better for Vista 64-bit. I doubt you can say this for any previous Windows 64-bit OS.
If you can't live with the issues, I'd say stick with XP 32-bit unless you really need the memory, in which case you are stuck anyway.
My main tip if you go the Vista 64-bit route is to get a large external USB or firewire drive and use it to make sure you have your backups and disaster recovery under control. Make heavy use of the system restore. Have backups before you attempt to install new software or drivers. Don't just install new stuff unless you need it. Think before you install stuff if you would expect it to work under 64-bit Vista.
Lots of stuff just works with Vista 64-bit. I have an OLD copy of Paintshop Pro for example which isn't Vista or 64-bit aware and it works fine. I have a number of old Hauppauge TV cards which will never work under Vista 64-bit however and had to move them to another machine.
I have an external disk and an internal disk both dedicated to backups. I run full image backups to the external drive and incremental file backups to the internal drive. Vista Ultimate has the image and incremental functionality built in and while it isn't overly flexible, it is well integrated. If you totally break the system, you should be able to boot from the install disc and restore an image from the USB drive.
This all assumes you can't run an OS like Solaris or Linux which do 64-bit well.
I run Solaris 10 64-bit and Gentoo Linux 64-bit (among others) under VMWare Workstation 6. I run both with the physical disk mode and 768MB RAM allocated to each virtual machine. I can run up to three virtual machines at once, and normally run two virtual machines with X windows in addition to various MS Windows applications. These VMs run well, including the X windows display.
All in all, I have Vista 64-bit doing what I need and it does it fairly well and is fairly stable. Most things work OK (like DVD playback, etc.). There are some nifty features (like integrated file restore with Vista Ultimate if you enable the file backup). It certainly isn't all that MS would like you to believe, but it can be made to work in most cases.
Good luck,
-john
Oh, expect a period of adjustment and time to get things working. I fought with a lot of things like getting security settings correct on my files after importing the hard drives from Windows XP, getting my network sharing working correctly, etc. It took a while and made me grouchy, but once things were working, life gets better.