On dual cores - 32bit or 64bit?

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thom_A
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On dual cores - 32bit or 64bit?

Post by thom_A »

We need someone to set this straight, considering there are usually 2 flavors of ISOs, 32bit and 64bit.

It's general knowledge that dual cores are technically 64bit-capable. What is really recommended? Sure, everyone says you only need 64-bit when you have more than 4GB RAM. So? Why not install the 64-bit then, what's the harm even if you have less than 4GB RAM?

(I will be testing the XFCE beta when it is released, so I have to make sure I'll be downloading the right ISO and not waste bandwidth downloading the wrong one.)
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Re: On dual cores - 32bit or 64bit?

Post by raphamotta »

In my opinion, if you have a 64bit capable, use the 64 bit version. I have a netbook with 2GB of ram and 64bit works very well, maybe better than 32bit version.

64bit uses a little bit more ram, but as I can see it's less than 5% more.
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Re: On dual cores - 32bit or 64bit?

Post by richyrich »

I have found that 64bit is slower and takes up more resources when I have less than 4 Gb of ram. 32bit is much snappier. :-)
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Re: On dual cores - 32bit or 64bit?

Post by thom_A »

richyrich wrote:I have found that 64bit is slower and takes up more resources when I have less than 4 Gb of ram. 32bit is much snappier. :-)
I have tried both (32bit/64bit) on dual cores. I couldn't tell whether one is "snappier" than the other. And since I have another computer which is quad core and with more than 4GB ram, it became convenient to just download one ISO, which is 64bit. But I'm still confused about this.
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Re: On dual cores - 32bit or 64bit?

Post by Pjotr »

I advise to select 64-bit whenever reasonably possible (i.e. 1 GB RAM or more). The 32-bit infrastructure is crumbling all down the line: no more 32-bit Google Chrome, no more 32-bit openSUSE, etc. etc.

Good old 32-bit is going the way of the floppy disk, the CD and the dodo bird....
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Re: On dual cores - 32bit or 64bit?

Post by sa3paleasm »

i run core2duo with 64 work good
try
uname -m
thom_A
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Re: On dual cores - 32bit or 64bit?

Post by thom_A »

I haven't installed a 32bit OS in years since I discovered my dual cores were actually 64-bit capable even if they're less than 4GB ram. I bought them years ago with Win7/Vista 32 bit installed, which got me thinking months later why 32bit, and not 64bit?

I'm revisiting this because I want to add Xfce to my multi-boot systems alongside Win7. I need something lightweight that is quick to load. I find Cinnamon taking time to load. KDE is my main OS. It will always be there no matter what. (There are no rules in how many OSes you want to multi-boot. It's your computer. You can do whatever you want with it.)

Porteus is probably one the quickest to load amongst lightweights, takes about 30 seconds. But I need something Ubuntu-based like Mint. So I'm looking forward to testing Xfce Mint 18.
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Re: On dual cores - 32bit or 64bit?

Post by rene »

The 4GiB boundary that you mention in your first post as being oft heard is equally oft based on missing understanding of "memory" versus "address space". A 32-bit CPU has a directly accessible 4GiB, 2 to the power 32, address space, but a standard 32-bit Linux kernel carves this up into 3GiB for applications and only 1GiB for the kernel. Of the latter 128MiB is reserved for various address-space demands, meaning that already if you have more than 896MiB of memory not all of it can be directly mapped into kernel space, with the remainder used as so-called highmem, mapped and unmapped on an as-needed basis. Highmem is not nice and not fast, and if you have 2GiB or more of memory more than half of your RAM is used in this manner; the output of "dmesg" on said 32-bit kernel will show you relatively near its start the amount of RAM used as highmem.

64-bit code and especially data is a bit larger than 32-bit. Code marginally so due to immediate operands but data more so due to pointers doubling in size. An oft quoted figure would find 64-bit code+data to be approximately 25% bigger than 32-bit. Especially seeing as how this means there fits less of it in the CPU caches this also means it's slower -- but at around the 2GiB memory mark this is offset by the speed-advantages of not needing highmem; a 64-bit kernel does not have the 4GiB address space difficulties.

That is; if you have less than 2GiB of memory go 32-bit. If you have 4GiB or more definitely 64-bit, although not really in an "obvious" sense but in the above sketched one. At 2GiB of memory I myself most certainly also already would although you might in a benchmark have trouble noting a difference.
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Re: On dual cores - 32bit or 64bit?

Post by Pjotr »

rene wrote:if you have less than 2GiB of memory go 32-bit.
Technically, you're right. This used to be my advice as well.

However, in view of the crumbling 32-bit infrastructure I've lowered my advice to less than 1 GB. Because I expect that more and more applications will become 64-bit only....
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Re: On dual cores - 32bit or 64bit?

Post by Hoser Rob »

I used to use 32 bit Mint on my 1Gb netbook but I reinstalled 64 bit when Google announced they would drop 32 bit support. The writing was on the wall. 32 bit Chromium is supported, yes, but how well and for how long?

And settng up Chrome is much less a headache for beginners ... it's hard for me to recommend 32 bit if you can run it because it's a Linux version that doesn't run Chrome. If you were talking about hardware that has to run in 32 bit I'd try a really light distro (eg. Puppy) that's meant for less powerful hardware.

Actually I do think 64 bit runs a bit slower on my 1Gb netbook. I doubt you'd notice the difference with 2Gb.
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Re: On dual cores - 32bit or 64bit?

Post by rene »

Pjotr wrote:However, in view of the crumbling 32-bit infrastructure I've lowered my advice to less than 1 GB. Because I expect that more and more applications will become 64-bit only....
Yes, that's fair enough I suppose. I would find it to be approximately 8 years since 32-bit was at all relevant. Which was also the exact time at which I stopped paying attention to the kernel-side of things; hence my enthusiasm for being able to speak of highmem once more. If anyone wants me to, I could go right deep into DOS-era extended memory, expanded memory and the intricacies of the HMA as well -- but I would at this point indeed sort of advise to no longer bother with it or 32-bit Linux :)
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Re: On dual cores - 32bit or 64bit?

Post by KBD47 »

raphamotta wrote:In my opinion, if you have a 64bit capable, use the 64 bit version. I have a netbook with 2GB of ram and 64bit works very well, maybe better than 32bit version.

64bit uses a little bit more ram, but as I can see it's less than 5% more.
I have a Chromebook that I legacy boot Linux on. Dual core and 2 gigabites of ram. I notice a big difference in 32 bit vs 64 bit. 64 bit is much slower, at least enough that I notice it. Also the Chromebook gets warmer, probably because of using more ram. At 4 gigabites of ram I imagine there would be no noticeable difference, but with dual core CPU and just 2 gigs of ram I certainly notice a difference. Also I wonder if 32 bit and using swap might also make the low spec computers run better/faster. I carve off a couple of gigs of swap for low ram machines.
Edit: Octane test 64 bit 8,000 but on 32 bit 11,000 (higher number is faster).
https://chromium.github.io/octane/
Last edited by KBD47 on Tue Jul 19, 2016 12:50 pm, edited 1 time in total.
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Re: On dual cores - 32bit or 64bit?

Post by thom_A »

rene wrote:That is; if you have less than 2GiB of memory go 32-bit. If you have 4GiB or more definitely 64-bit, although not really in an "obvious" sense but in the above sketched one. At 2GiB of memory I myself most certainly also already would although you might in a benchmark have trouble noting a difference.
Two of our dual core PCs in this household got 3Gb ram, one of which was upgraded from 2Gb ram, and the other one which is a laptop got 4Gb ram.

I find that 3Gb is enough for most purposes. 2Gb is still like gasping for more memory especially when you're running multiple windows. You won't even have to add more to make it 4Gb because I find that that the extra 1 Gb is not being used. Unless, of course, you are running a 3d software or some memory intensive program. So all in all, 3Gb ram, in my opinion, is just right.

Anyways, you still have to address the software part in an age where 32 bit apps are getting fewer and fewer as mentioned by others here.
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Re: On dual cores - 32bit or 64bit?

Post by rene »

thom_A wrote:Two of our dual core PCs in this household got 3Gb ram, one of which was upgraded from 2Gb ram [ ... ]
So they are using one 2GiB DIMM and one 1GiB one I gather. That automatically means you are running your RAM in single-channel mode whereas if you'd remove the 1GiB DIMMs and stick in two with the already used 2GiB DIMMs compatible 2GiB ones you'd (generally, I guess I should say) get to run them in dual-channel mode. Much more important than the additional 1GiB and certainly on older machines, when RAM speed was severely lagging, this would double the bandwidth available between RAM and chipset/cpu and would, I feel, be a near insult to your systems to not do.

Anyways. In either case and certainly for the 4GiB laptop 64-bit would be the right answer. And just to clarify, in the above quote where I say "not really in an obvious sense" I find that upon rereading badly put. Certainly when you have 4GiB or more you should be using 64-bit also in the obvious sense; it was said obvious sense not being the first one to consider that I was commenting on; 64-bit to in my view being already recommended for two GiB or more. Or 1GiB as we as per Pjotr's reaction count "crumbling 32-bit infrastructure".
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Re: On dual cores - 32bit or 64bit?

Post by Proxima »

I don't really understand what the number of cores has to do with anything here, there are even single core CPUs (like (some)Pentiums 4 or Athlons 64) that support it, what really matters when you make the choice are mostly the amount of RAM and secondly software support (like Pjotr's reasoning).

The latter is sole reason I chose 64bit on my laptop (#1 in signature) - things are just dropping support for 32bit systems and this trend is inevitably going to continue and spread.

On the other hand, I wouldn't ignore the downside of more memory usage by 64bit OS & software if you have less than 4GB.
Using Mint 18 x64 on that rig for a while now I've noticed that it can run out of RAM juice reaally quickly, with just google earth open for a couple minutes (I'd recommend reducing google earth caches to minimum if you like using it) or while browsing the net with sometimes just 3-4 tabs open.

Therefore one thing that I'd recommend is to NOT reduce swappiness (or reduce it less, to 30-40) on 64bit Mint (at least 18 with Cinnamon) with 2GB or less RAM. It's easy to hit that 2Gigs limit and once you do, the system suddendly goes full panic mode, trying to swap out as much as it can pretty much freezing the system making it unusable for quite a while (depending on how fast your disk is). Just let it swap out stuff gradually.

No idea if there's a noticeable difference in performance between 32 and 64 bit systems on a rig with 2 or less Gigs, might test it one day, but right now don't have any extra disk space for another OS.

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Re: On dual cores - 32bit or 64bit?

Post by MtnDewManiac »

thom_A wrote:It's general knowledge that dual cores are technically 64bit-capable.
General knowledge is obviously lacking, lol. There have been dual-core CPUs that were 32-bit. I know, because my old laptop had one. It was an Intel CPU, T2250 IIRC (but I would not swear to it).
rene wrote:The 4GiB boundary that you mention in your first post as being oft heard is equally oft based on missing understanding of "memory" versus "address space". A 32-bit CPU has a directly accessible 4GiB, 2 to the power 32, address space, but a standard 32-bit Linux kernel carves this up into 3GiB for applications and only 1GiB for the kernel. Of the latter 128MiB is reserved for various address-space demands, meaning that already if you have more than 896MiB of memory not all of it can be directly mapped into kernel space, with the remainder used as so-called highmem, mapped and unmapped on an as-needed basis. Highmem is not nice and not fast, and if you have 2GiB or more of memory more than half of your RAM is used in this manner; the output of "dmesg" on said 32-bit kernel will show you relatively near its start the amount of RAM used as highmem.
Clem's 32-bit releases do not use a "standard 32-bit" linux kernel, they instead use PAE ones. Does that change the significance of anything you've stated (in practical terms)?

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Re: On dual cores - 32bit or 64bit?

Post by thom_A »

MtnDewManiac wrote:General knowledge is obviously lacking, lol. There have been dual-core CPUs that were 32-bit. I know, because my old laptop had one. It was an Intel CPU, T2250 IIRC (but I would not swear to it).
Thanks. I stand corrected.

Let me just conclude by saying I won't be replacing these still very usable systems anytime soon. Can't even say they're old because I know the big difference compared to what we had before. They won't be given away anytime soon. And I will continue to use 64bit until I see concrete evidence the other is faster.

The OS itself will tell you whether your system is 64bit capable or not. If it is, then we can go from there and ask what is recommended. I'll appreciate it if you focus on the purpose of this thread in your next post.

(I'll be testing the just released Mint Xfce beta. The 64bit, of course.)
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Re: On dual cores - 32bit or 64bit?

Post by rene »

MtnDewManiac wrote:Clem's 32-bit releases do not use a "standard 32-bit" linux kernel, they instead use PAE ones. Does that change the significance of anything you've stated (in practical terms)?
No. The PAE situation was cunningly encoded in the two words "directly accessible" in my above statement which I thought I'd get away with here on the Mint forum.

The original PAE, Physical Address Extension, technology adds 4 bits to the 32-bit physical address for a total physical address space of 64GiB, 2 to the power 36, but only in a global sense. The CPU architecture is itself still fully 32-bit and deals with 32-bit addresses only. Each individual process is therefore also with PAE still limited to a directly accessible 4GiB space, with only the kernel having the option of having that 4GiB space be for separate processes windows onto separate 4GiB physical memory regions (well, see later). This means that the above 3-1 kernel/user address space split features issue-wise unchanged between PAE and non-PAE kernels.

Now that you got me to expand though, I should really also specify that the split is really itself a "mere" optimization. Explicitly noting PAE to until further notice not feature in this, certainly the kernel could in fact elect to give both user and kernel a 4GiB address space each, and back when 32-bit was still relevant patches to that effect existed. With, again, the CPU architecture fully 32-bit this however means that a process needs to address through a different set of page tables -- structures that provide for translation from the by kernel and processes spoken virtual addresses to physical addresses -- depending on whether it's running in user- or kernel-mode since each single set, a page directory, can only deal with 4GiB.

These page tables reside in memory themselves and are cached on-CPU in what is called the TLB, the Translation Lookaside Buffer. When switching tables upon a process' entry into the kernel and again upon return to user space we need to invalidate this cache, need to "flush the TLB", and start repopulating it directly from memory all over again --- and this is one of the slowest things you could imagine your CPU to be doing, certainly back then when memory-speed was hugely lagging CPU clock-speed. Linux wants/ed to at all cost avoid this TLB flush penalty, hence shares the same set of tables between user and kernel space, hence allows for per-process 4Gib total only.

In the 32-bit kernel configuration you can adjust the standard 3-1 split to 2-2, 1-3 and two slightly tweaked version of the first two but the 4-4 option you will not find. Note also that with for example the 1-3 split you now of course only have 1GiB for user space and that the 32-bit machines with back then large amounts of memory that technically would've wanted a bigger kernel space tended to have said large amounts specifically to for example run large databases in user space, thereby wanting a large user space as well. There was and is really no good solution even technically other than going 64-bit once you go over 2GiB physical, or even 1GiB/896MiB already as per original reply and standard setup.

PAE -- a slight further note. After all this page table switcheroo talk you could be wondering if as long as per above the kernel has with PAE the option to address 64GiB of memory total, then why couldn't it through for the purpose specific interfaces provide this option to individual process? Conjuring up images of also already mentioned DOS-era expanded memory, the answer is that it technically could. And that as far as I am aware it has never, with steady stomach, considered doing so. Single user-addressable structures would still be limited to (less than) the user space size, and the model would be an utter mess generally. Also see the bit above about 64-bit entering at the point where any of this became even halfway relevant in the first place.

So, no, PAE does not change this specific issue. And see how those two words "directly accessible" were much shorter than the above? :roll:

Let me then finally note that PAE has been part of the CPU architecture since the Pentium Pro (1995) and the phrase "standard kernel" would at this point include PAE kernels. In this case I used the adjective "standard" to refer to a 32-bit kernel configured for a 3-1 split rather than the other options. And finally-finally, that our current AMD64 architecture started life as an extension of PAE by AMD -- but that otherwise one should at this point feel perfectly free to consider PAE even less relevant than 32-bit in and of itself.
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Re: On dual cores - 32bit or 64bit?

Post by BG405 »

Rene that post was really interesting to read, thanks!

I'd like to add my 2p worth. Using 64-bit Mint you can still run 32-bit software, in my case Google Earth v7.1.4.1529 32-bit and it works very well indeed. My only issue is the printer driver won't (yet) work on 64-bit, a subject for another thread.

I'll definitely be giving Mint 18 KDE 64-bit a run on my Acer dual-core netbook with 2GB RAM to see how well it works. I'll report my findings on this.
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Re: On dual cores - 32bit or 64bit?

Post by rene »

Netbooks tend to feature non-powerful CPUs with, specifically relevant to the situation, small on-die caches. With then moreover KDE living in the general memory- and specifically pointer-hungry C++ universe you just may have there picked one of the best opportunities to find a 64-bit install to lag a 32-bit install on a 2GiB system. I expect that more 32-bit data fitting in your L2 cache will have you find the the 32-bit install to be snappier, perhaps significantly so.
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