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RAM

08/14/2009 6:51 AM

My PC has 2gb PC6400 RAM (400MHz), and I have a old 1gb PC3200(200 MHz) stick lying around. Do you think it would make any difference, or do you think it would slow the pc down? All is DDR2 unbuffered.

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#1

Re: RAM

08/14/2009 9:40 AM

Probably won't work at all unless you drop the FSB down to 200MHz, which would seriously slow you down.

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#2

Re: RAM

08/14/2009 12:08 PM

Hello Bondy:

Don't Do It. First PC6400 is DDR2 and is rated at 800 MHz, PC3200 is rated at 400 MHz.

The memory clock would have to be set to accommodate the PC 3200, and therefore your data transfer through the PC 6400 would basically be cut in half.

The confusion in the bus speed is that DDR 3200 actually runs at 200 MHz but reads on the rise and falling edges of the clock signal i.e. double data rate so you have an effective 400 MHz. And the PC 6400 runs at 400 MHz but likewise has a effective clock speed of 800 MHz.

Also depending on the configuration of the motherboard you could have dual channel memory. Basically you're reading to individual strips of memory simultaneously, in order to do this the memory must be or at least should be matched.

Basically in the worst-case scenario the effective memory speed could be reduced by 75% i.e. if the board was reading dual channel and defaulted to single channel mode and was adjusted to operate with the DDR 3200.

http://en.wikipedia.org/wiki/DDR_SDRAM

http://en.wikipedia.org/wiki/Dual-channel_architecture

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#3
In reply to #2

Re: RAM

08/14/2009 12:34 PM

Hello again Bondy:

Let me apologize for the sloppy editing of the first line. I was editing the post to reflect that the PC 3200 is available in both DDR and DDR2 the latter being signified by PC2 3200, and ran out of time. When I look back at the post it sounded like a derogatory comment and it certainly was not meant that way.

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#4
In reply to #3

Re: RAM

08/14/2009 4:14 PM

Nah, that's fine - You had such a thorough explanation of it. I was thinking that it would read it separately and just add to the ram, rather than slowing it all down to the slowest's speed.

GA for your answer btw

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#5

Re: RAM

08/14/2009 11:02 PM

DDR and DDR2 are not compatible. Even if they were, your RAM speed is only as fast as the slowest memory module.

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#6

Re: RAM

08/15/2009 2:43 AM

There is PC3200 DDR2, and you wont have a problem using both the PC6400 and the PC3200 together, the only thing is that you will not be using a feature called Dual Channel anymore. Dual Channel gives you a 10% speed boost over not using it. You need matching sets of memory to use Dual Channel. Also the system will default to the speed of the slowest stick of ram. With 3gb of ram you may not even notice a difference. Try it and see what happens. You may need to check the voltage and cas of the older stick, it needs to be at least the same voltage. Some motherboards let you tweak the voltage settings, just don't get to aggressive, you might blow your rig up. DDR2 memory is very cheap nowadays, so maybe it's better to buy two 1 or 2 gig sticks for your 'puter to keep it running fast. Hope this helps, Mike.

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#7
In reply to #6

Re: RAM

08/15/2009 2:45 AM

Will it be using Dual Channel even though I only have a 2 gig stick of RAM in at the moment?

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#8
In reply to #7

Re: RAM

08/15/2009 2:50 AM

You need two or four sticks to run in Dual Channel. If you add the other 1gb stick, the computer might slow down.

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#12
In reply to #7

Re: RAM

08/15/2009 9:31 PM

Hello Bondy:

It seems you've been getting some good advice. Not all boards are set up to run dual channel memory. One way or the other if you're running a single 2 GB memory module you're not running in dual channel mode.

Although the performance increase varies by application the10% number someone else quoted is probably a good all-around estimate.

You could check your motherboard manual to see if the board is capable of dual channel operation, if so it might be worth your while to go by a matched set of 2 GB memory modules.

If you decide to go this way you also should check and see what the fastest memory your motherboard will support is. Sometimes OEM manufacturers will not put the fastest memory in their systems if there is a considerable price difference.

Recently the price of PC2 8500 (1066 MHz) has fallen considerably. So you'd really be in luck if you're motherboard supported the PC2 8500 and dual channel operation, it then would probably be worth your money to upgrade your system.

More memory never hurts, and at the price of RAM nowadays you could probably justify doing it no matter your motherboard limitations are, but it's doubtful that you would notice the difference.

It really depends on what you're doing with the machine. For example being an hotrodder , I just had to make the computer go faster (habit) it's an overclocked quad core Pentium with a 2 TB raid array, that I built from scratch.

My wife uses a $250 e machine with a Celeron processor. On most applications the only real difference I noticed is the time it takes to programs to load, besides that there is very little difference. On processor intensive applications like video crunching mine is over six times faster.

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#13
In reply to #12

Re: RAM

08/16/2009 4:24 AM

It can support Dual Channel, but it only supports up to 800MHz RAM (PC5300?). I don't know if the fsb has any part in this - that is 2000MHz.

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#14
In reply to #13

Re: RAM

08/16/2009 10:30 AM

Well I think you've got an extra zero in that front side bus. The front side bus speed is set to match the CPU .

The memory speed is determined by using a multiplier for example a 200 MHz fsb will use a multiplier factor of 2 to utilize 400 MHz memory, Wikipedia does a much better job of explaining this than I can.

Back to your machine, PC 5300 is rated at 667 MHz again for the example the multiplier factor for this memory would be approximately 1.67 = 334 memory frequency times 2 for the double data rate and we end up with 668 megahertz, well I told you it was a approximately.

In your particular case if you're using PC2 6400 which has an effective bus speed of 800 MHz it is not running at full speed. The memory can only run as fast as the board will allow.

That's no problem, you can always put faster memory in, however it will still be limited by the motherboards capability.

In your case if I were attempting to use the dual Channel capabilities and wanted to add memory I would replace it with PC2 6400. My reasoning is there is very little price difference, and if you get a newer machine that can handle the faster memory you can always use the memory to upgrade that machine.

Next all memory is not created equal. The memory timings are more aggressive on the premium or high performance memory, so memory running at the same speed can have different data transfer rates, again nowadays there is very little price difference between premium and economy memory so I would get good memory.

The only caveat to this is when purchasing memory. Some of the high-performance memory requires a higher voltage setting, all motherboards may not be capable of doing this, so make sure the memory will run at the standard voltage which is 1.8V.

Just in case it comes up there may be a update for your bias that would allow you to use faster memory, if you haven't done this before I would not attempt it. If something goes wrong you basically killed the motherboard.

http://en.wikipedia.org/wiki/Front-side_bus

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#15
In reply to #13

Re: RAM

08/16/2009 6:53 PM

It looks to me that you have an AMD processor. When you use Dual Channel, the total clock speed on some motherboards tends to slow down. My machine uses 1066Mhz ram, but when in Dual Channel mode it runs at 800Mhz. My CPU FSB is 2000Mhz because its AMD. Even thou the memory clock speed slows, the gain using Dual Channel is greater then the loss. When I build a computer to sell, I rather install two 1 or 2 gig sticks rather that 1 two or four gig sticks. The performance gain is greater the the Dual Channel that not using it. For your rig I recommend you buy a 2 gig stick to match the one already installed. Just make sure the CAS is the same and it should run in Dual Channel mode. I hope this helped, Mike.

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#9

Re: RAM

08/15/2009 4:49 AM

all will simply run at 200mhz if you had 400mhz + 200mhz inserted

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#10

Re: RAM

08/15/2009 9:22 AM

As all memory sees the same clock, the clock would need to run at the slowest speed.

The following is not an answe to your question, but is relevant in case someone extrapolates the answer incorrectly:
It is possible to use memory of similar type (same clock speed and DDR number) that have different delays (CAS ratings) from each other without penalising the faster memory. However, the arrangement of the memory needs to be controlled so that the two types of memory are not addressed simultaneously.

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#11
In reply to #10

Re: RAM

08/15/2009 7:04 PM
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#16

Re: RAM

08/17/2009 2:48 AM

Thanks everyone!

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#17

Re: RAM

10/24/2009 11:02 PM

Check with a computer store they can tell you if it will work if you tell them the specs of your computer.

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