Can 64 bit 10.04 overwrite 32 bit 9.10 without probs

Yes. HUGE issues.

I would recommend simply reformatting the hard drive (after backing up your files) and then performing a clean install of Ubuntu 10.04LTS. An upgrade is going to go 32-bit to 32-bit or 64-bit to 64-bit, but not 32-bit to 64-bit.

You can use dpkg to export a list of installed applications on the current system and then also use dpkg to install those applications on the new system. Normally I would suggest just backing up your entire /home directory with all of its' .hidden folders, files and settings, but again, since you are migrating from 32-bit to 64-bit, I think it's best to just start all new to mitigate as much risk as possible between the 32-to-64-bit migration process.

If you were just upgrading from 9.10 to 10.04LTS and staying on 32-bit, then I'd suggest just backing up the /home directory as mentioned above.

I was running 64-bit Ubuntu 9.10 for short while because there are multiple programs that are not supported by the 64-bit version. I really like Firefox and Thunderbird but many of the plug-ins and add-ons were not compatible (I believe many developers only built for 32-bit Linux Distributions). My suggestion is to verify if there are any programs, etc., that you currently run if they are available or supported on the 64-bit version.

The above answers of backing up your /home directory or other files is usually the answer most people come to as being the best route.

While I do not know if it's possible with i386 to amd64, I do know that I was able to move off lpia to i386 on my netbook. lpia is a subset of i386 (an lpia processor can run i386 code but not vice versa). The situation is very similar (to my knowledge) to the relatonship betwen i386 and amd64. Thus, using the steps I used for lpia to i386 (and substituting when necessary), you may be able to make something work.

steps for lpia to i386 migration

Sadly, it's a big pain to do and it may or may not work. Backup before trying for sure as you may blow things up.

Some of the posts touched on whether you should stick with 32-bit. A huge reason to upgrade from 32-bit to 64-bit is memory restrictions in the default 32-bit kernel. You can work around this limitation by enabling the PAE module in the kernel. Performance benefits between 32-bit and 64-bit are overblown (not huge, but they exist). If you need to go through a large ordeal to switch architectures and you don't need more than 4 GB of memory, you will most likely be disappointed in upgrading to amd64 as it will be almost exactly the same.

"Thanks for that. In view of the other responses I received, would you think that I am losing anything significant on my 64 bit Sempron by running 32 bit code? TVM louis – lescrooge 5 hours ago"

Hi lescrooge,

Well, there is a lot of differences between 32 and 64 bit systems and their architecture. Hardware-wise and software-wise, they are different, so I won't go over specifics, but very, very, very generally speaking.... if you have a 5 gallon bucket of water full of 5 gallons of water, that's 32-bit. Now if you were able to put 10 gallons of water in that same 5 gallon bucket, that's 64-bit. Same space, twice the machine instruction. Again. this is very general.

Are you losing anything by running 32 bit software (OS and programs) vs running the 64 bit versions? Well, that kind of depends. For say word processing, you won't really see a difference. Nor will you notice it for sending and receiving email either, so if what normally do doesn't need 64 bit to be optimized, no, you aren't losing anything. In fact, you may GAIN some things by staying at 32 bit. For example, Flash is horrid under 64 bit. It's buggy, flawed, crashed, etc. 32 bit version on a 32 bit OS is much better. Also, there isn't going to be any real performance gain noticeable enough on 64 bit vs 32 for you to notice in Flash. Now other things, yes, there is a HUGE difference, so again, it just kind of depends on what your needs are, what you do on your PC, which programs you run. In the Windows world for example, Playing WoW (I'm not a gamer, but a friend of mine is), there is a HUGE difference between the 32 and the 64 bit versions of the game. WoW 64 bit blows 32 bit away, and although I've never seen WoW ran under Linux, I hear it excels there as well.

Sorry to be so long-winded, but there isn't really a concise, one-answer-fits-all answer for you on this topic. for ME, I know that it doesn't really matter either way, because of what I do, whether it's a 32 or 64 bit system. I'm personally waiting for 64 bit to become more stable and common place than it currently is. Yes, the hardware is out there, but the software needs to catch up. 32 bit IS a dying breed, but it seems like the changeover from 23 to 64 is going much slower than the changeover from 16 bit to 32 bit went, in my opinion.