RAM upgrade backwards-compatibility

April 10, 2009 3:40 PM

Is DDR2 PC2-6400 memory backwards-compatible with a laptop that uses DDR2 PC2-5300?

The brick & mortar store has 200 pin PC2-6400 in stock and for the same price as their out-of-stock 200 pin PC2-5300 selection. FWIW, I have a Dell Inspiron 6000 laptop.

posted by DB Cooper to computers & internet (7 comments total)

Yes. From wikipedia:

Higher performance DDR2 DIMMs are compatible with lower performance DDR2 DIMMs; however, the higher performance module runs at the lower module's frequency. Using lower performing DDR2 memory in a system capable of higher performance results in the bus running at the rate of the lowest performance memory in use.

posted by GuyZero at 3:53 PM on April 10

Yep, you're fine. You won't see the benefit of the greater speed, but it's not going to hurt anything.
posted by Netzapper at 4:10 PM on April 10

Thanks, guys!
posted by DB Cooper at 4:13 PM on April 10

I tried putting DDR2 800MHz RAM in a MacBook and it would only work if one of the sticks was 667MHz. If both sticks were 800MHz it wouldn't boot.

So, just wanted to say that while the RAM can run at the slower speed, the motherboard might be incompatible with the higher speed. If you buy it, make sure you can return it without too much grief.
posted by kamelhoecker at 4:30 PM on April 10

From what I have heard from multiple sources, both in a professional environment where laptops were upgraded and from computer stores; laptops are more picky in different RAM speeds and may not always be compatible in the same way as desktop memory. Buy the slower RAM, you won't notice the speed difference.
posted by Sonic_Molson at 5:17 PM on April 10

"laptops are more picky in different RAM speeds and may not always be compatible in the same way as desktop memory."

^^^ not true in the least. Sorry. I've put higher-than-spec'd ram in major laptops from HP to Dell to Toshiba to IBM to Sager. Never once had an issue that was ram speed related. I've seen laptops not like high-chip count dimm's though (cheap ram).
posted by SirStan at 6:04 PM on April 10

I've had laptops reject some RAM, but i don't think it was for BUS speed issues, but as SirStan said more about the quality of the RAM. Laptops are indeed pickier about some things.
posted by sycophant at 6:09 AM on April 11