Problems with DDR2 PC2 6400 RAM in Macbook

Have the same issue with my 6400 RAM's, any can help to resolve without changing to 5300?

Jason Moore3 wrote:
I have a late 2007 Macbook (2.2GHz Intel Core 2 Duo MB062LL/B). When I went to the store to buy 2 sticks of 2GB - they were sold out of the PC2 5300 (667MHz) so I payed a few bucks more for the PC2 6400 (800MHz).

I figured the Macbook would simply run the memory at the lower speed. When I replaced the two 1GB sticks, with the 2GB sticks, it refused to boot. (No sounds. No beeps. Nothing.)

I proceeded to them try various combinations of ram. What I found was that if I had a 512MB stick (PC2-5300) then the 2GB stick (PC2-6400) would work fine. If I just had the PC2-6400, it wouldn't boot at all.

I realize that I probably need to return the PC2-6400 for PC2-5300 - but I'm curious if anyone can explain this behaviour.

How can fast RAM cause problems? (Doesn't the RAM simply operate at whatever speed the bus sends data to it?)

Is this a bug in the MacBook firmware? It detects how fast the memory how fast can run, and then barfs when the memory says 800MHz (instead of the expected 667MHz?)

I doubt it's a problem with the firmware. All the memory stuff is done by the Intel chipset's memory controller. These controllers seem to have certain combinations that work OK, while there are others that don't. I have heard reports that PC2-6400 doesn't work by itself, although I hadn't heard of different combinations being tried.

I've tried different combinations in my MacBook, including dual PC2-4200 modules and mixed PC2-4200 and PC2-5300. The memory controller (chipset) datasheet notes that when two different speeds are used simultaneously, the controller defaults to the slower one for both. That was my experience, as System Profiler said both were running at 533 MHz which indicates PC2-4200 speeds.

Apparently it just doesn't get past power on self test. It theoretically can run at lower clock speeds, but in your case using a PC2-5300 module caused the entire system to revert to PC2-5300 speeds. If there's any limitation, it's all going to be hardwired into Intel's memory controller. When it reads the serial presence detect EEPROM on each module, it probably doesn't like what it sees.

I have a similar problem. I have an early 2008 15" MacBookPro4,1 2,4 Ghz, which came with 2 1 Gb 667 MHz DDR2 modules.
I bought a Kingston 4Gb kit that has 2 2Gb 800 Mhz modules (model No. KTA-MB800K2/4GR).
The Kingston specs state they will work with MacBook Pro and they are intended to be used with Apple systems requiring 800, 667 or 533 MHz DDR2 memory modules.
They do not work.
I called Kingston support, they say my computer should be able to use this memory, recommended me to look up for firmware upgrades. I did, but I already had the latest for my model (Boot ROM Version: MBP41.00C1.B03 SMC Version: 1.27f1). Called them again, they say the memory should work, but it's my Mac that is not "talking" to them properly telling them to change the operating mode to 667.
Anyone has come across this memory? Any solutions?
(I live in Spain and bought this at BestBuy in the US - BTW the guy at BB said they would work "for sure" - so not easy to change them).

Hi acovi: 800mHz RAM is the incorrect spec for your computer. You need 667nHz PC-5300 RAM as stated in the owners manual.

Stedman

Thanks for your reply Stedman.

I realize they are not the right memory, and I had also read the manual before buying this memory. My mistake, I know. The reason I bought them was that they had a good price, the agent at BestBuy told me they would work, and the specs in the Kingston box ("intended to be used with Apple systems requiring 800, 667 and 533 MHz DDR2 memory modules") clearly deceived me. Lesson learned: always trust your Apple specs and manual.

I will speak with Kingston. I think their advertising and specs are misleading.

Cheers

And BTW, as stated previously in this thread, I can get one my original 1 GB 667 Mhz to work with one of the 2 GB 800 MHz modules to get a total of 3Gb.
My About This Mac box says: 3 GB 667 MHz DDR2 SDRAM
My System Profiler:
Memory: 3 GB
Bus Speed: 800 MHz

Cheers

Hi acovi: Yes, that seems to be the common issue. The 800mHz RAM will work when installed with one of the 667mHz chips, but not when there are 2 of them installed.

Enjoy
Stedman

I have the same MacBook Pro model number, I tried the same memory as you (also purchased from Best Buy), and I have the same results! No boot... I wish I had read this thread before I purchased this RAM. Oh well, I'm returning the memory now, I wish I had read this thread earlier.