Advantages of 64 bit versions of a distro (or otherwise)
 

Hi

I recently upgraded my PC to a Pentium D dual core processor. I have not used a 64 bit processor before, but in the past I have noticed that some Linux distros have 64 bit versions. I understand that there is very little speed difference between 64 and 32 bit computers, but is there any particular advantage or disadvantage to using a 64 bit distro as opposed to the same distro in its 32 bit configuration?

For example, I currently have several 32 bit Linux distros on my old hard drive (as I have not yet decided which distro I prefer). Is it better to transfer the partitions holding these distros onto my new hard drive, or would it be better for me to download their 64 bit equivalents instead? I keep most of my current data in a separate Common Data partition that is accessible by all of the distros, so the retention of that data should not be a problem regardless of which way I go.

The greatest advantage is that you can address more RAM.
As my rule of thumb: if you have more than 4 GB of RAM, go 64 bit, if you have less than 2 GB of RAM, go 32 bit.

In between, you can choose. If you use precompiled software from proprietary vendors, it is easier to use a 32 bit distro.

That's my €0.02

Thanks Janhe

That's a good rule of thumb that is worth remembering.

My PC currently has 2GByte RAM that can be upgraded to 4, so that puts me firmly in the "in between" category. On that basis I will transfer my current Linux partitions from my old hard drive, which should save me a fair amount of time as opposed to reinstalling all of them.

Although, just for fun, next weekend I may try installing the 32 and 64 bit versions of Ubunto 9.04, just to see if there is any difference in performance.

Here's an article comparing the two versions:
http://www.tuxradar.com/content/ubun...bit-benchmarks

The difference in general is not that great, overall I've found most programs to open and run slightly faster on 64-bit, around 1 sec or so.

In order to notice a significant difference you would need to have greater than or equal to 4GB of RAM, or you will also notice a significant difference in programs that crunch numbers, including transcoders, encoders, decoders, scientific programs, etc. Make sure to install a recent version of nasm and yasm, because these help a lot in significantly improving 64-bit performance. Some encoders are able to use x64 assembly to greatly speed up encoding.

Other than that, you may need multilib or a 32-bit chroot if you want to run 32-bit programs like wine.

brianL

Thanks for the link that you provided, it certainly provides a good overview of what I can expect from running 32 or 64 bit distros. I was especially interested in the time difference between converting WAV files to OGG as that is something that I intend to do quite a bit of. I just loaded both the 32 bit and the 64 bit versions of Ubunto 9.04 onto my PC, so I will check out the difference in conversions times myself this weekend.

H_TexMex_H

From the very brief time that I have the 32 bit and 64 bit versions of Ubunto 9.04 running, I would agree that I have not seen any significant difference in performance, although at this stage I have not tried to run any programs that perform heavy number crunching. In addition I still only have 2 Gbyte of RAM installed, so some potential advantages of having 64 bit processing capability may be lost to me.

My PC is able to address up to 4 Gbytes of RAM, so my next aquisition will need to be the additional 2 Gigs. My PC has 4 channels into which RAM can be installed. It currently has a single stick of 2 GByte DDR RAM installed in one of those channels. I have been advised that I will get a better boost in performance if I add another 2 Gbyte stick into the matching channel to the one that is currently populated, as opposed for example to installing two 1 GByte sticks in the other two channel pairs. Is anyone able to confirm whether or not this is correct, or even if it will make any difference at all?

Regarding your recommendation to install nasm and yasm, I am not a programmer, so it is unlikely that I will use these directly. I have no issues with installing these if they will be beneficial in any way, but am I likely to get any such benefit if I don't do any programming myself?

When I moved over to Linux earlier this year, I was tempted to retain Windows XP for a few Windows programs that I am very fond of and which I have yet to find a really good Linux equivalent; especially Noteworth Composer, a music composition program. As recorded in a previous thread I accidently deleted my Windows partition. Although this was a tragedy of Greek proportions at the time, I have decided to make the most of it by making a clean break from Windows altogether. So far, so good. So hopefully I will resist the temptation to instal Wine to get some Windows compatibility.

nasm and yasm are used when compiling various video encoders and such, so you will NOT be using them directly, they are used to generate executables. And really, if you don't compile the encoders yourself, then you don't really need them. It depends on if your distro has a package for these or if you decide to compile them yourself.

You should check the manual on whether the mobo supports that scheme for dual channel, I know mine does tho, so like this:

Channel A
DIMM 0 (blue) - 1GB
DIMM 1 (black) - 1GB

Channel B
DIMM 0 (blue) - 2 GB
DIMM 1 (black)

That will work on my mobo, but some mobos may not support this. (colors are arbitrary)

I don't know about music composition, I know I once tried rosegarden:
http://www.rosegardenmusic.com/
and it was reasonably good, if not, maybe search sourceforge or freshmeat for more.

The 64 bit advantage in video and audio format conversion (in programs that are coded and compiled to have such advantage) is mostly independent of memory size.

I'm not sure what those connectors are correctly are called, but not "channels". Your PC has 2 channels for ram.

Absolutely! You want a matching stick in the other connector of the same channel. Edit: Oops, I said that backwards. I meant the corresponding connector of the other channel.

For tasks in which your L2 cache is very effective, using dual channel will make a small difference. For tasks in which the L2 cache is less effective, dual channel will make an enormous difference. I don't know what kind of tasks you will be running.

If your BIOS believes a second 2GB stick is compatible enough with the first and is plugged into the correct connector, then all 4GB will be used in dual channel mode.

If you add two 1GB sticks and get all the positions right, I don't know whether that would let the new 2GB of ram work in dual channel mode with the old 2GB staying single channel, or whether it all must be single channel. I also don't know how performance effective the result might be.

Hi,

Actually it boils down to the MB design whether the multi-channel support is there. Most current consumer MB support a single memory channel with interfaces to the memory controller to support dual channel functionality with the proper connectors for pairs. You don't necessarily have to use matched pairs but things are much easier if you do. If you don't have matched pairs you sometimes can adjust the CPU clock down to allow dual channel with unmatched pairs. Some advantages to doing this but at the sacrifice of lower CPU clock times.

For the bottleneck problem we do use dual channel memory so as to provide active data availability to the CPU via the cache. Your data is hopefully there for the cache via the channeled memory when the controller switches;

The above is excerpts from the wiki but does provide a great definition. See the wiki!

The big advantage of 64 bit is the data pathway along with accessibility of larger address range and CPU cycles. The big disadvantage of 64 bit is that not all 32bit applications have not nor may not evolve to 64 bit. That's why a lot of arguments are made to have multi-lib systems.

Thank you
 

H-TexMex_H, johnsfine and onebuck

Thank you for your advice regarding the advantages of 64 bit and installing memory modules. I was finally able to locate and download a copy of the manual for the motherboard that is installed in my PC. For the record it is a Gigabyte GA-81949P Pro, and it does include support for Dual Channel DDR 2. The manual recommends that where more than one memory module is used then they should be of similar capacity, specifications and brand. I am not sure that I can get exactly the same brand, but it sounds like I would be better of getting a 2 GByte memory module. Although the manual indicates that a single memory module can be used, but only as a single channel, it does not say what effect using 3 memory modules would have with regards to dual channel functionality.

johnsfine

You were quite correct to say
I was unaware when I used the term "channels" that this was a technical term used for a different but related purpose. I just called them "channels" because that is what they looked like t me. However, according to my manual the correct term is "socket". So, my motherboard has four sockets and two channels. As my current 2GByte memory module is in socket DDR II 1, I will need to obtain another 2 GByte module and install it in socket DDR II 3 in order to make use of the dual channel functionality.

I would like to ask one more question if I may. I tried research this on the internet, but I could not find anything that provided a clear cut answer. As my PC came with a 2 GByte memory module installed, it is obviously cheaper for me to just purchase another 2 GByte module, installed as above, and thus have one channel working in dual channel mode. However, in terms of overall efficiency, and ignoring economic arguments for the moment, would I get any difference in performance if I was to remove the 2 GByte memory module and install 1 GByte memory modules in each of the 4 sockets, thereby allowing both channels to work in dual channel mode instead of just one. I suspect there would be no difference in performance at all, and that my question is akin to asking, "Would my car run better with two small petrol tanks instead of one big one", but I am curious.

You mean one pair of sockets working in dual channel mode. That is most efficient.

There is a significant possibility for reduction in performance. I don't know if there is any chance of increase.

Some older designs could interleave memory as well as using channels in parallel, so the recovery time of each memory stick would be overlapped with operations on the alternate stick. But I don't think the memory controllers for four stick DDR2 can do that.

Each stick wired in parallel adds electrical capacitance, which slows the maximum clock rate at which the memory operates. Some BIOSs may actually detect this and actually use a lower clock rate when four sticks are used rather than one dual channel pair. (More likely, the BIOS runs even one dual channel pair at the speed that would have worked for four sticks and only manual overclocking would be faster with just the single dual channel pair).

A bit more info to consider (though I am not including links to any scientific studies at this time):

1) For the record, I detected no obvious improvement or regression on my machine after going from 2 1-Gib sticks in dual channel mode, to 4 1-Gib sticks in dual channel mode ((2 @ dual-channel) x2) other than that I had _more_ memory. The clock speeds of the memory didn't change from what I have them set at, regardless how many sticks are in there. Keep in mind though, different motherboards may also have different wiring depending on how the particular manufacturer has intended for the slots to be used; johnsfine's right-- there could be a decrease in performance with one setup vs. another.

2) Several sites where benchmarks have been done on this sort of stuff, claim that higher-capacity modules tend to be slightly 'slower' than lower-capacity modules; so a 2-Gib stick would be slightly slower net access-time etc., than a comparable 1-Gib stick.

3) FWIW, the OP could probably put two new 1-Gib sticks in the first 2 slots, and simply move the existing 2-Gib
stick to the 3rd slot (provided the motherboard/BIOS will allow this); it's a compromise between what he and johnsfine are discussing: two less sticks to buy (compared to 4 new 1-Gib sticks) = less $$$ spent, and three sticks all together with only ONE pair in dual channel mode = less electrical capacitance.. And, the OP still ends up with 4-Gib of RAM. Plus, the two new sticks can/will be matched to each other.

Sasha

Yeah, it's possible as I mentioned earlier, but I'm not sure all mobos support this. Also, all sticks would be in dual-channel mode, in fact, I believe that dual-channel is an all-or-nothing kind of deal, it's either on or off for all sticks. All that is needed is for each channel to have the exact same total size of RAM, and you can add the capacity of memory sticks together if they are in the same channel.