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#1 2009-09-29 22:16:14

jamtat
Member
Registered: 2008-03-13
Posts: 224

hardware upgrade questions

This is a bit OT since a lot of it's not Arch-specific. But I am an Arch user. And at least some of my questions will have to do with migrating over an existing Arch install.

Well, it's getting about time to do a system upgrade. Not something I look forward to, but my current machine is starting to do some weird things which I'm interpreting as signs of the imminent demise of this hardware.

I want to state up front that I favor trailing edge hardware. That is, I wait at least a couple years after new technology has hit the scene and prices begin to drop to reasonable levels before I consider upgrading anything. As you might guess, this means I'm still stuck n the age of 32-bit computing.

The target machine I'm replacing has a Semron 3000+ CPU, so I'm looking to upgrade to soomething a little better than that. I'm currently debating whether to get something dual core or just a single core machine: P4 3.0's are pretty reasonably priced these days, and that should be a decent upgrade over my current system.

One of my main questions is about going with a dual-core CPU. One of the factors dictating me going with a single core machine is that's what I'll be migrating from--and I'd like to preserve as much of my current installation as will be possible. I'm aware that many dual-core CPU's are still 32-bit, but here's the rub: aren't applications unable to make use of both those cores unless they've been compiled with special SMP (symmetric multi processor) flags? If not, what's the point of having two cores? As you can see, I'm a bit in the dark about whether your average Linux distro (like Arch) is really set up for dual-core architecture. Any enlightening remarks on this, anyone?

I think my reason for wanting to steer clear of 64-bit CPU's should be clear (want to try and preserve my current, 32-bit installation, if possible). So let's say I get this P4 3.0 machine I'm talking about. Can I just slap the HD's from my current machine (yes, they're SATA and the new machine has SATA headers), boot it up, and expect to hit the ground running? My Arch installation is pretty up-to-date, btw.

I know there's a risk in taking this approach. I've done it with a few Win systems and, so long as the computer has access to the i386 directory on the HD or an installation CD, it's worked ok. But I've done this less frequently with Linux systems. Anyone have experience doing something like that? I think, at the least, I'd have to switch to a different kernel, since I've selected to run the AMD-optimized kernel on the current machine.

Finally, I'll probably be doing some (home) video editing on the target machine. I know from experience it takes more horsepower than my Sempron 3000+ can put out. Anyone know if a P4 3.0 is going to perform much better with video editing tasks? I'm aiming at 2 GB RAM, which I know is considered low in this day and age. And of course another key question is HD space: I might end up having to throw another HD in there. But at the moment I want to ask mainly about CPU power: should I expect much better performance from a P4 3.0 (Prescott, I believe) for video editing than I get with my Sempron 3000+?

Input will be appreciated.

Thanks,
James

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#2 2009-09-30 01:14:41

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

If I read this chart http://www.anandtech.com/cpuchipsets/sh … i=2149&p=7 correctly, it doesn't look like a P4 3.0 is much of an upgrade, if any, over my Sempron 3000+. I'm not a doom player, nor do I play any kind of comuter games whatever, so I'm not sure if those results are totally relevant to my uses. As I mentioned, video editing is one of the things I'd like to do and would probably be the most CPU-intensive task this machine would perform. Input, anyone?

Thanks,
James

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#3 2009-09-30 02:23:24

Chrysalis
Member
Registered: 2008-07-07
Posts: 155

Re: hardware upgrade questions

Booting in fallback image and reinstalling the kernel should be all (assuming you are using stock kernel)

The CPU being 64bit doesnt prevent you from running your 32bit OS.

Also, throwing money at a decade old system is sorta pointless without moving to a new platform.

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#4 2009-10-15 17:36:27

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

I'm back at this and have to do something soon. My current machine is powering down randomly more frequently now. A close inspection of the innards inidcates to me that the mobo has bad caps syndrome.

Can anyone recommend to me an inexpensive 32-bit dual-core CPU/mobo combo? I'm not trying to be cutting-edge here, like I said. My usual tack is to buy leftovers of what was cutting-edge several years ago and that now has come down to reasonable prices. I found a good price on the Asus AT3GC-I, but on further reading I gather that the CPU's are 64-bit. How about the Core 2 Duo E5200? Is that one 64-bit?

So a 64-bit CPU will run a 32-bit OS, as Chrysalis says. But what are the drawbacks? Will the OS be able to access all the RAM? If anyone can point me to a good tutorial on 64-bit vs. 32-bit systems, that would also be helpful.

Advice needed soon.

Thanks,
James

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#5 2009-10-15 21:48:45

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

Ok. I finally found something that addresses some of my key questions. See http://www.linux.com/archive/feature/123800 . Any other input on this topic anyone?

Thanks,
James

PS Another discussion that touches on many of my questions: http://www.tomshardware.com/forum/24991 … -dual-core

PPS Yet another discussion of dual-core CPU's with some 64-bit CPU comments thrown in: http://www.trap17.com/index.php/Pro39s- … 38600.html . And then this: http://www.devhardware.com/forums/intel … 88189.html

Last edited by jamtat (2009-10-15 22:32:18)

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#6 2009-10-16 12:35:35

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

If I understand correctly what I've been reading related to my questions over these past couple of days, the following conclusions can be drawn. As I suspected, for at least 2 or 3 years now all new CPU's produced and sold in most stores and/or by online retailers are dual core CPU's. Secondly, all those CPU's are also 64-bit-capable CPU's. Why do I emphasize the word capable? Because these are not true 64-bit CPU's, as I understand it, but are 32-bit CPU's that have been modified to handle 64-bit code (or the 64-bit instruction set, as it's sometimes said). That's why they can run 32-bit OS's and programs just as effectively as they can 64-bit OS's and programs. Now, if I were considering buying a "pure" 64-bit CPU system like, say, the Itanium, there would be no way around an OS re-installation. This sort of pure 64-bit CPU has not been modified to handle the 32-bit instruction set and so doesn't know what to do with a 32-bit OS and associated programs. But as I said, it seems that there are very, very few such CPU's on the market now--and this is bound to be most true of the end-user market. The Itanium, after all, turned out to be something of a fiasco for Intel and they ended up copying AMD's strategy, which was to modify 32-bit CPU designs to handle 64-bit code rather than producing a true 64-bit CPU that would (or would not, as the case may be) be backward-compatible with 32-bit code. In reference to my questions, there's no worry about installing--or transferring over--a 32-bit OS to one of these modified 32-bit CPU's--whether dual or single core. The only issue that might arise using a 32-bit OS on one of these relates to RAM: if I were to have more than 4 GB RAM (I don't and don't plan on having that much anytime soon), the 32-bit OS would not be able to use all of it.

Does it sound like I've understood correctly the basic issues at stake? Any corrections/modifications/additions to what I've said? Input will be appreciated.

James

Last edited by jamtat (2009-10-16 13:40:00)

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#7 2009-10-16 13:48:39

perbh
Member
From: Republic of Texas
Registered: 2005-03-04
Posts: 765

Re: hardware upgrade questions

any intel/amd cpu be it 32-bit or 64-bit, will only be able to use 3+GB of memory if running a 32-bit OS.
This is inherent in the fact that pointers are 32 bits and thus have a restricted addressing range.

The only _real_ difference between 32bit OS and a 64-bit OS is that pointers are 64 bits in the latter case, ints are still 32 bits, but longs are 32 bits in the first case, 64 bits in the latter.

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#8 2009-10-16 15:01:21

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

perbh wrote:

any intel/amd cpu be it 32-bit or 64-bit, will only be able to use 3+GB of memory if running a 32-bit OS.

My reading indicates that the 32-bit RAM usage limitation begins at 4 GB. To restate this using your phrasing would be to say "any intel/amd cpu be it 32-bit or 64-bit, will only be able to use 4+GB of memory if running a 32-bit OS." So, are you saying stuff I've been reading is wrong and that the 32-bit OS RAM limitation starts at 3 GB and not at 4 GB?

James

Last edited by jamtat (2009-10-16 15:01:58)

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#9 2009-10-16 15:36:20

SapiensAntiquus
Member
From: Minnesota, USA
Registered: 2009-05-05
Posts: 14

Re: hardware upgrade questions

This is just a guess, but sine we are talking about the limitation of the pointer size to address the location in memory, doesn't that mean that we have 2^32? Which puts us at 4294967296 (4.3 GB).  I don't really know much about it, but that's what it sounds like.

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#10 2009-10-16 17:37:44

perbh
Member
From: Republic of Texas
Registered: 2005-03-04
Posts: 765

Re: hardware upgrade questions

yup - but there _is_ other stuff - which we are not allowed even toi peek into (Ulrich Depper had an excellent article - well, 6 chapters of it - check up lwn.net around may/june sometime) on how memory works. Basically - any single application is limited to 2 gigs
All told - you will not be able to use more than 3.2 gig of memory (on a 32 bit OS), no matter how much you have installed.
However, if my memory serves me right, there is a PAE-mode that can be used and which will allow more than 3.2 gigs to be used.
1) PAE-mode is generally _not_ set in most kernels, but if you roll your own, it should be possible.
2) I don't know exactly _how_ this works, but I would think that a user-addressable application is still bound by the 2 gigs - though I may be wrong

and Sapiens - you are quite right. a 32-bit pointer will NOT be able to address more than ~4 gigs

Last edited by perbh (2009-10-16 17:39:41)

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#11 2009-10-18 09:15:46

Chrysalis
Member
Registered: 2008-07-07
Posts: 155

Re: hardware upgrade questions

What does that have to do with you choosing a CPU to buy? Everything out there is 64bit unless you somehow manage to dig out a dusty athlonXP or p4.

About the 32 vs 64bit OS, its as simple as that - if you have 4 gigs or more ram go 64bit, if not 32bit. (you must me smoking something to put this much ram on such an old machine while being cheap on the CPU)

Last edited by Chrysalis (2009-10-18 09:16:43)

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#12 2009-10-21 03:32:09

jamtat
Member
Registered: 2008-03-13
Posts: 224

Re: hardware upgrade questions

I swapped in the new mobo today (Athlon 64 X2 dual core 5400+ cpu) and it has worked out pretty well. The system wouldn't boot using the default kernel (as expected) so I went ahead and booted the fallback, which worked fine. Once there I did a kernel reinstall. Apart from that I just needed to modify /etc/modprobe.d/modprobe.conf (new sound chip on this mobo) so as to get my two sound cards once again initializing in the proper order and I was good to go. It's hard to believe this all went so smoothly. Try doing something like that, you smug Windows users: your OS is gonna go wacky and only a repentant call to big brother stands a chance of getting your machine back to anything like normal working order. Linux has Windows beat all to hell in this respect. Of course it helps if you've got just a wee bit of geekosterone, which I, as a Linux user of about 8 years seem to have now.

James

Last edited by jamtat (2009-10-21 13:37:22)

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