My mobo is failing and I have to replace it. Computer hardware has progressed and my old 'socket A' is way out of date. The new mobo & cpu will be 64 bit; still Amd. Can I simply put it together with my harddrive and boot up? Will the 64 bit cpu run a 32 bit system?

As far as 32 bit vs. 64 bit kernel I believe that the 32 bit kernel is going to provide the same performance on a workstation and will give you fewer problems with drivers. The 64 bit kernel is mostly for using a huge RAM configuration. Other than that there is no significant performance gain using the 64 bit kernel.

You can certainly try plugging your configured hard drive into a new computer. If you are using a Linux distro that is configured to use modules rather than putting all of the drivers into the kernel then you might get it running on the first try. In theory it should work. In practice you'll just have to try it and find out.

Yes, you can run a 32 bit OS on a 64-bit CPU. I've used a variety of 32-bit OS's on my Athlon 64. As for using the old hard drive, it should work. But, I can't guarantee anything.

Thanks. Right now, I'm using the kernel 2.6.17-2-k7. I'm running Etch. How much is a "huge RAM configuration"? My new memory will be a gig.

When you have > 4gb a 32bit kernel needs to reserve a hole in the memory that costs you something like ~500mb so if using 4gb you actually get ~3.5gb usable. You should be alright on putting in the old drive but will probably have to reconfigure the sound card, maybe nic but a kernel that new should have support for the new one and possibly the video card if you specified a BusID in the X config if that changed or brand of card changed requiring new driver.

1GB is not huge. 4-16GB is huge. uP are designed to be backwards compatible. By design a 64-bit processor will run 32-bit applications (those tricky engineers). Same thing happened when 16- and 32-bit uP hit the market.

Note that this is different from certain operating systems that require new, state-of-the art, NASA hardware to run. Oh, wait, NASA is using Gentoo in one of their latest projects.

My video card is an ATI 7000 VE, which runs on DRI. It's old, but reliable. I intend to keep it for a while as it runs without proprietary drivers.

I don't see a big difference in RAM use between my 64 and 32 installs.For sure nothing near the double some guys are raving about.