about RAM

tokoro · 2013-06-20 15:28:45

I know this is a newbie question, but I really don't know much about hardware.

I want to change to a 64 bit OS, but I only have 2 GB of ram (I haven't needed more). My motherboard only supports DDR2 and has 4 slots in 2 channels. What would be the best configuration for that? I would like to get at least 8 gb.

Is it worth it to change my motherboard so that it supports DDR3? How can I know my current dimm's latency?

The motherboard comes with this warning

Due to AMD CPU limitation, DDR2 1066 is supported by AM2+/AM3 CPU for one DIMM per channel only.

Does that mean that if I wanted to use 1066 latency sticks I can only have 2 of them?

Thanks for your help.

drcouzelis · 2013-06-20 16:06:37

tokoro wrote:

I want to change to a 64 bit OS, but I only have 2 GB of ram (I haven't needed more).

You don't need more RAM, even with a 64-bit operating system. But that doesn't mean you don't want more RAM...

WonderWoofy · 2013-06-20 16:12:24

I honestly don't see what the advantage to moving to a 64-bit system would be, unless you actually do upgrade to more than 3GB of RAM. Most places will tell you more than 4GB, but in actuality, a 32-bit system cannot fully utilize 4GB of RAM, so I always tend to think over 3GB justifies 64bit.

I think the question is whether you really need to do this or not. You even say yourself, you have had no reason to add more RAM, so what has changed? If you use swap space, and you see heavy swapping, then you probably need more RAM. If not, then you aren't filling your RAM anyway, so there is really no point in getting more for it only to sit unused.

falconindy · 2013-06-20 16:31:22

Fact: A 32-bit system cannot properly utilize more than 1gb of ram.

tokoro · 2013-06-20 16:41:11

I have recently changed from gnome to KDE and at some points it starts to swap a lot. Also I have made some deep recursion programs that get killed due to lack of memory, but they just need a couple more of gbs.

What I'm saying is that I need at least 4 gB of ram. I know that even with 32 bits I can read more than 4 gb, but I really think it's time to take the 32bit leap.

Now my question is about latency. Does it really makes a big differerence? I'm thinking that with my current machine plus the 8 gb of ram I cant still work and play properly for at least 2 years, and by then I would have enough money to build another awesome rig.

Are there any caveats I need to worry about or is just to put as much ram with the highest latency I can afford?

falconindy wrote:

Fact: A 32-bit system cannot properly utilize more than 1gb of ram.

Why 1 gb and not 3.x ? there are also some nice cpu features that are not being used.

Last edited by tokoro (2013-06-20 16:54:35)

falconindy · 2013-06-20 17:15:21

tokoro wrote:

falconindy wrote:
Fact: A 32-bit system cannot properly utilize more than 1gb of ram.
Why 1 gb and not 3.x ? there are also some nice cpu features that are not being used.

Because your 32-bit x86 processor is simply not capable of addressing enough virtual memory to accommodate the physical memory. CONFIG_HIGHMEM is a kernel hack which allows userspace processes to address past the 1GB mark. However, your PCI devices still will not be able to access memory over the 1GB mark.

Related: http://cl4ssic4l.wordpress.com/2011/05/ … about-pae/

geno.nullfree · 2013-06-20 18:01:09

falconindy wrote:

Because your 32-bit x86 processor is simply not capable of addressing enough virtual memory to accommodate the physical memory. CONFIG_HIGHMEM is a kernel hack which allows userspace processes to address past the 1GB mark. However, your PCI devices still will not be able to access memory over the 1GB mark.
Related: http://cl4ssic4l.wordpress.com/2011/05/ … about-pae/

Very nice. When I first read this I wanted to dispute your claim about the 1GB limit, because I had always heard 4GB(3.x). Reading through your link and googling some more led me to [http://archive09.linux.com/feature/119287] where it finally clicked and I realized there are more or less actually two flags for PAE (I previously thought it was just an on/off 4GB/64GB switch), one flag enables up to 4GB (CONFIG_HIGHMEM4G, default for 32-bit kernels now I assume) and another (CONFIG_HIGHMEM64G) to enable 64GB of RAM. That is, if I'm understanding this correctly. Just wanted to say thanks.

Edited: readability

Last edited by geno.nullfree (2013-06-20 18:12:24)

mich41 · 2013-06-20 21:02:58

Numbers like 800, 1066, 1333 indicate frequency, not latencies. Latencies are completely different animal and actually they are very similar on all non-$$$ DDR2 and DDR3 sticks.

FWIW, I don't feel any difference between 1066 and 1600 in "light" applications (coding, web, etc.). Most games don't care either since they are usually GPU-bound. RAM frequency shows mainly on benchmarks or applications which crunch huge amounts of data and take hours to complete. RAM latencies barely make a difference even there.

Due to AMD CPU limitation, DDR2 1066 is supported by AM2+/AM3 CPU for one DIMM per channel only.

This means two sticks, one per channel. Check your motherboard's manual to find out how slots are connected to channels.

If you really need fast RAM, DDR3 may let you use four 1066MHz sticks or even four 1333MHz sticks. Also, it can be cheaper than DDR2 if high capacity DDR2 sticks are no longer easily found on your local market - do some research before buying. Note that only AM3/AM3+ CPUs (Phenom II, Athlon II, FX) support DDR3 and some AM3 Athlons II are limited to DDR3-1066 (four sticks, though). If you find AM3+ and AM3 mobos for similar price, get AM3+ as it'll give you option to upgrade CPU to FX.

You can find current settings in BIOS setup. You can also downclock RAM temporarily and check whether it makes any difference in your applications.

IMO a reasonably priced 2x4GB DDR2-1066 set will be fine for such machine. DDR2-800 wouldn't be bad either because a 4x2GB set should be really cheap. If you feel that DDR2-800 is too slow and 4GB DDR2 sticks are expensive, check prices of DDR3 and AM3/AM3+ mobos - this is current production stuff, easily available and inexpensive.

Last edited by mich41 (2013-06-20 21:50:05)

tokoro · 2013-06-20 21:56:13

mich41 wrote:

IMO a reasonably priced 2x4GB DDR2-1066 set will be fine for such machine. DDR2-800 wouldn't be bad either because a 4x2GB set should be really cheap. If you feel that DDR2-800 is too slow and 4GB DDR2 sticks are expensive, check prices of DDR3 and AM3/AM3+ mobos - this is current production stuff, easily available and inexpensive.

I haven't checked if my cpu supports ddr3, and it seems that I'm out of luck here. Its an AMD Phenom 9950. So I guess I'll be stuck with ddr2 for a while.

Is it okay to mix several sticks of different sizes?

Arch Linux

#1 2013-06-20 15:28:45

about RAM

#2 2013-06-20 16:06:37

Re: about RAM

#3 2013-06-20 16:12:24

Re: about RAM

#4 2013-06-20 16:31:22

Re: about RAM

#5 2013-06-20 16:41:11

Re: about RAM

#6 2013-06-20 17:15:21

Re: about RAM

#7 2013-06-20 18:01:09

Re: about RAM

#8 2013-06-20 21:02:58

Re: about RAM

#9 2013-06-20 21:56:13

Re: about RAM

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