Tom's Ultimate RAM Speed Tests

The article mentions a couple of times that you need a 64 bit operating system to utilize 4 GB or RAM because 32 bit (XP for instance) can only access 3 GB of memory.

1) Is it true that 32bit XP can only access 3GB? I thought it was 3.5GB...

2) If I build a system and load it with 4GB of memory, will 32bit XP work well enough (only accessing it's 3GB or 3.5GB maximum) or will it have difficulty running properly? Meaning, is it preferable or necessary to build a 32bit XP box with only 3GB exactly?

Great article, thanks.

B.

The article mentions a couple of times that you need a 64 bit operating system to utilize 4 GB or RAM because 32 bit (XP for instance) can only access 3 GB of memory.

1) Is it true that 32bit XP can only access 3GB? I thought it was 3.5GB...

2) If I build a system and load it with 4GB of memory, will 32bit XP work well enough (only accessing it's 3GB or 3.5GB maximum) or will it have difficulty running properly? Meaning, is it preferable or necessary to build a 32bit XP box with only 3GB exactly?

Great article, thanks.

B.

Yes XP32 can access 3GB, but it subtracts the amount of RAM on your video card from that. So if you have 512MB or RAM on your video card, XP32 would only see 2.5GB of system RAM. I went through this last week when I upgraded to 4GB RAM, so I switched to Vista64. Gaming rig. No regrets.

How does XP64 do these days? Is there better driver support?

"More memory, meaning 4 GB, requires a 64-bit operating system..."

Except it doesn't. 32bit Linux can use in excess of 4GB of memory, though not on all chipsets. I was looking at this issue only yesterday. I was unable to see 4GB with a motherboard using an Intel 945 chipset but on with an Intel 965 chipset I was able to see all 4GB just fine using the bigsmp kernel.

Anonymous said:

How does XP64 do these days? Is there better driver support?

I find that XP64 does quite well. I've had it on one of my computers for a year now and have had no driver troubles. That's one thing I think Vista 64 has been for, getting the hardware companies to finally make 64 bit drivers. Also, in comparing my machine with XP64 and the one with Vista 64, the XP64 is much easier to use. Of course, the XP64 does not support gaming with DX10. I'll be building a new office machine during the next month and after using Vista 64 the past few weeks on my gaming machine, I'll install XP64 on the office machine.

As to the article on the ram, I didn't see it answer anything new, only confirm what was already thought. One poorly written part was page 4, "How ram sensitive are different CPUs?" The following paragraph didn't seem to address the opening line at all. Even in the conclusion of the article, there was not much said to answer the question, just an allusion that memory type was was of small relevance to either of the CPUs.

The actual amount 32-bit Windows can see without Extended Memory Addressing turned on is 3.3GB. This is a result of the OS using the addresses past the 3.3 boundary for addressing hardware, etc. Having 4GB in your system will not affect your performance.

Linux can address more than 3.3GB and beyond with the 32-bit kernel using the same means the Windows Server variants can, by using Extended Memory Addressing, and it's support is dependent on the memory controller and BIOS, as well as the OS.

Well according to Microsoft's website, Vista 32-bit can now fully use 4gb of RAM without subtracting off the total memory in your computer.

Here is the article:

http://technet2.microsoft.com/WindowsVista/en/library/005f921e-f706-401e-abb5-eec42ea0a03e1033.mspx?mfr=true

Scroll down to the "General Improvements and Enhancements" section. It is the second bullet point. Just thought I would point this out seeing as there is a RAM limit with 32-bit XP.

Something seems wrong with the data on page 3. Both DDR2 and DDR3 have a single clock that runs at the same speed at the I/O bus - for example, a DDR2-800 module has a 400MHz clock. What the table calls an "I/O clock" sounds more like the data strobes, which are not clocks. They also run at the same speed as the I/O bus, but are not free-running, like the clock. They only run when there are I/O operations. It looks like somebody confused CKE or CS with the clock. Either that, or there's a fundamental misunderstanding about what the "8 bit prefetch" is.

32bit operating systems can support a maximum of 4gb of ram. but you must subtract video ram and cpu cache from this total.

@hawk4031, you need to read that more carefully "Windows Vista will report the amount of system memory installed rather than report the amount of system memory available to the OS"

this means that windows will report the 4GB, but you still wont be able to make use of it all.

So I am reading the article and thinking it makes more sense to buy a less expensive board and RAM and use the money you saved on the CPU instead. Even for overclocking this can make sense as more expensive chips have higher multipliers, making exotic RAM even further less important.

digibriHow does XP64 do these days? Is there better driver support?

I was an early adopter of XP64. I figured, AMD 64 4000+ is a 64 bit processor and I should have an OS that ran 64 bit. There are issue still to this day, specially with running dos stuff - but nothing that DOSBox can't get around.

As for drivers, it's a lot better than 2 years ago. I couldn't print, I couldn't use my creative webcam (on of the more expensive ones back in the day) and a couple other devices. Most of drivers I needed are now available, minus any of the scanners I had (Dropped off Goodwill).

hawk4031Well according to Microsoft's website, Vista 32-bit can now fully use 4gb of RAM without subtracting off the total memory in your computer. Here is the article:http://technet2.microsoft.com/Wind [...] x?mfr=trueScroll down to the "General Improvements and Enhancements" section. It is the second bullet point. Just thought I would point this out seeing as there is a RAM limit with 32-bit XP.

According to that document, 32bit Vista will "report" all 4GB. That's not the same thing as being able to fully use 4GB. It was changed to avoid confusion. The available memory limitation still exists.

Silly question... building a new PC
Is it worth getting 4 1g sticks of DDR2 800MHZ RAM 3-3-3-10
ram can be seen here http://www.ocworkbench.com/2007/kingston/low-latency-cas3-ddr2-800/g1.htm

or worth me getting 4 2g sticks of ram like this
http://www.i-tech.com.au/products/23829_Transcend_JM800QLU_2G_2GB_800MHz_PC2.aspx

I was going towards the 4 low latency 1g sticks, but i can get 4 2g sticks of normal latency ddr2800 ram for about the same price which one would i be better off getting?

this article is full of anomolies.The bias to upgrade without facts ought to be criminal. I am running a p4 2.8e until the gov't steps in and says it is as crooked as a monopoly to claim 12800mbyte /sec from 200mhz. Mutlithreading and actual work stopped lying to me at the anything but a dual core 2.8e-3.4ee in 2003. From there on out, a bad bad hoax. Keep paying kids...this is crazier than a 5 main boxer engine. And lastly, I am a full house on 242 watts(supposedly). did someone mention old p4 was power hungry? How much proof, or how many perfect hours , and electric bills and lack of repairs does a home builder need to stomp at these billionares....Evolution Stopped. More than myself has proven it. Step up to dual core for no reason, other than security (that is honestly the only thing I have noticed- I am not joking) It further proves they split data, not sped it up. A bird with one mouth gets a big ol' hack doesn't it...

I use Windows XP Pro x64 and absolutely love it. There are occassional issues with hardware compatibility if you're recycling old parts, but usually (more often than not) you can find a solution that works. Or you can just get hardware that will work regardless. The major driver issues are usually related to competitors (iTunes, Palm, BlackBerry, etc.) where synchronization is typically an issue. There are workarounds, usually.

Despite that, I'd never go back to 32-bit OS's. I have 4 GB of RAM in my system and it screams. I can throw anything at it ( www.PeterSouza.com/computer - specs). I used to have 8 GB, and will again, after having just upgraded from 800 MHz to 1066 MHz DDR.

There seems to be some confusion as to the limit in XP, but if memory serves me right this is how it goes.

Every piece of hardware attached to your computer uses part of the address space (32 bits wide in this case), the reason video cards are so famous is because they are the largest subscribers. Windows XP cannot use RAM that is not addressable after all the hardware have been assigned addresses which is the reason it varies.
That means a 1 GB video card takes 1GB out of the address space, not available RAM. The misconception may come from the fact that most video drivers reserve space for transfering data to the video cards in system RAM, and therefor may make it unaddressable to other applications.

just wondering... i have a laptop that says it supports 2 gigs max ram on the tech specs and it's running xp, 32 bit i belive. is that max ram based on the os or the hardware?

The fact that so disparate memory specifications ended up in so tiny difference simply does not seem to be logical. There are at least two factors to consider: 1. the CPU does not demand enough bandwidth and 2. the applications you utilizes do not demand enough memory bandwidth. I explain:

1. If you are testing high end memory modules, you should employ high-end processors and even high end system boards. You could try a motherboard which supports 2, 4 or 8 Opterons, for example. In this scenario, in particular with modern Opterons with 8 or 12 cores each, you would have enough processing power demanding memory bandwidth.

2. You could employ test suites specially designed to test several system components. They are specialized applications which employ different methods and algorithms, which provide accurate results in the end. Games load data in the graphic card and simply send commands to them, relieving the CPU (and the main memory) from demanding computations.


The fact you are using mostly games and 'mundane' applications for your tests can make sense to most of your visitors (and I understand what your audience is), but if you'd like to be absolutely fair and accurate in regards to these results, you should consider a professional test suite.