the difference between PC2-6400 and PC2-5300

PC2-6400 operates at 800 MHz PC2-5300 operates at 667 MHz

Your Mac requires one or the other -- do not put in the wrong speed, either higher or lower.

Putting in higher speed RAM than your Mac is designed for will give no benefit, and in some Macs (Penryn MacBook Pros most commonly) will crash the machine.

Putting in lower speed RAM will either crash the machine, or cause it to run at slower speeds.

Guides: Mac Hardware: Understanding Intel Mac RAM

krisapple80 said:

Thanks for looking.

Please can someone tell me what the difference is? I've searched the web and found that it is the peak transfer rate.....??? like that helps....

If i installed the 5300 memory rather than the 6400 would I notice the difference between them?

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PC2 5300 speed is 667Mhz. PC2-6400 speed is 800Mhz. If your system is designed for PC2-6400, it may or may not run on the PC2-5300. If it does run it will be slightly slower.

For more info http://en.wikipedia.org/wiki/DDR2_SDRAM

My understanding was that faster speed memory is back wards compatible long as it's the same type of dimm DDR2. So 800mhz memory can work on 667mhz machines just you won't benefit form the faster chips.

scuzy said:

My understanding was that faster speed memory is back wards compatible long as it's the same type of dimm DDR2. So 800mhz memory can work on 667mhz machines just you won't benefit form the faster chips.

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That sounds right to me. I'm pretty sure those 2 speeds are the same size because I just had that choice on the Dell I just ordered. Why the heck they offer a choice (it was $10 extra for the 800mhz on 2GB!!) is another story.

But those model number really mean nothing. They're just model numbers representing the different speeds. Try putting in a certain number (PC5300) in Wikipedia and you'll find out what it is.

For matching memory, go to http://www.crucial.com. They can tell you what you can use and even have an app that will scan your machine. Note ECC vs. non-ECC.

scuzy said:

My understanding was that faster speed memory is back wards compatible long as it's the same type of dimm DDR2. So 800mhz memory can work on 667mhz machines

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Except when it doesn't, as in the Penryn MacBooks.
Or when the module assembler hasn't written the SPD values properly.

There's no benefit to putting 800 MHz RAM in a 667 MHz memory bus Mac, and there is some risk of failure.

They can tell you what you can use and even have an app that will scan your machine. Note ECC vs. non-ECC.

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No current Macs take ECC RAM except the Mac Pros and Xserves. ECC was an option on the PowerMac G5's that nobody ever used. Other than that, Macs are non-ECC all the way.

CanadaRAM said:

No current Macs take ECC RAM except the Mac Pros and Xserves. ECC was an option on the PowerMac G5's that nobody ever used. Other than that, Macs are non-ECC all the way.

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Didn't know that's how the Mac line went with ECC. I just wanted to make sure people trying to buy knew it because it's not one of those things listed very well quite often. Memory makers should get the folks that did Target's prescription labels to make RAM packages. Give us the PC5300 or whatever number, bus speed, pins, and ECC/non-ECC in big, bold letters. Don't do the crap where the model number is the biggest number seen, which means NOTHING unless you look on the manufacturer's Web site.

I'm using core 2 duo. Its installed pc2 5300u 1gb.
After i found a pc2 6400 (ddr2 SDRAM). So i installed it by removing my pc 2 5300u ram card. Now i'm use pc2 6400 and pc2 5300 in 2 solt.( only 2 ram sholt) .but read only pc2 6400. Ather ram is not reading. Why is that?.
Please can you email me?
isharasandaru1@gmail.com