Macbook not recognizing 2x2gb 800mhz

[Luzzio]

I got a pair of Sodimm Kingston RAM's at 2gb 800mhz a piece.

I installed both at first, and the Macbook did not start up. The white light appeared, and I could feel the HD spinning, but there's nothing on the screen.

Swapped the first slot from the left with my old 512mb, making it 512mb 667mhz + 2gb 800mhz, and it worked with Macbook recognizing 2.5gb @ 667mhz.

Swapped the 2gb stick with the other 2gb, and it also works, meaning there's no faulty ram here.

I bought the 800mhz so I could use it for my next Macbook, which I heard would be utilizing 800mhz RAM sticks.

Quite sure the MB can handle 4gb (though recognizing at only 3.3gb), so is the mhz of the RAM the problem? I bought my Macbook in February.

Thanks.

 

[Chundles]

I got a pair of Sodimm Kingston RAM's at 2gb 800mhz a piece.

I installed both at first, and the Macbook did not start up. The white light appeared, and I could feel the HD spinning, but there's nothing on the screen.

Swapped the first slot from the left with my old 512mb, making it 512mb 667mhz + 2gb 800mhz, and it worked with Macbook recognizing 2.5gb @ 667mhz.

Swapped the 2gb stick with the other 2gb, and it also works, meaning there's no faulty ram here.

I bought the 800mhz so I could use it for my next Macbook, which I heard would be utilizing 800mhz RAM sticks.

Quite sure the MB can handle 4gb (though recognizing at only 3.3gb), so is the mhz of the RAM the problem? I bought my Macbook in February.

Thanks.

The MacBooks can only use 667MHz RAM, there is a timing issue that renders 800MHz RAM incompatible.

 

[jackiecanev2]

MB's with the Santa Rosa chipset will recognize 4GB of ram; pre-SR MB's will only be able to address 3.3GB. What are the specs of the MB? Just from the info at hand, I would suspect that you have a pre-SR machine.

Oh, and I believe Chundles is incorrect. Though SR does not support 800mhz memory bus, it will automatically downclock the memory to 667mhz. There is absolutely no reason that it should prevent recognition of all 4GB. The only machines that had issues addressing all 4GB were pre-SR, which Apple officially spec'd at 2GB max, though we all have learned that they can address a maximum 3.3GB if 2x2GB sticks are inserted.

 

[Luzzio]

Though SR does not support 800mhz memory bus, it will automatically downclock the memory to 667mhz. There is absolutely no reason that it should prevent recognition of all 4GB. The only machines that had issues addressing all 4GB were pre-SR, which Apple officially spec'd at 2GB max, though we all have learned that they can address a maximum 3.3GB if 2x2GB sticks are inserted.

I bought the two sticks based exactly on that.

I'm using a C2D, 2.0ghz 80GB (now 160gb), 1GB ram (before the upgrade), X3100, White, no superdrive.

 

[Chundles]

MB's with the Santa Rosa chipset will recognize 4GB of ram; pre-SR MB's will only be able to address 3.3GB. What are the specs of the MB? Just from the info at hand, I would suspect that you have a pre-SR machine.

Oh, and I believe Chundles is incorrect. Though SR does not support 800mhz memory bus, it will automatically downclock the memory to 667mhz. There is absolutely no reason that it should prevent recognition of all 4GB.

That's true - only problem is that it doesn't.

The current crop of MacBooks with the 800MHz FSB do not support 800MHz RAM. They just don't. We've determined it to be a timing issue - something to do with gates and stuff - techy talk that went way over my head - that means the RAM simply won't work if it's 800MHz.

 

[jackiecanev2]

That's true - only problem is that it doesn't.

The current crop of MacBooks with the 800MHz FSB do not support 800MHz RAM. They just don't. We've determined it to be a timing issue - something to do with gates and stuff - techy talk that went way over my head - that means the RAM simply won't work if it's 800MHz.

You're partly correct. MB's do not "support" 800mhz ram, because the 800mhz FSB is bottlenecked by the speed of the memory controller, which still tops out at 667mhz. However, the memory should automatically downclock to 667mhz and work just fine. This has worked for most all MB's until Penryn, and the theory should hold true for Penryn as well. This said, there has been a problem with some brands of 800mhz ram in Penryn units; SPD values being off, therefore not working in PENRYN MB/MBP's, unless one of the other sticks is Apple ram or 667mhz ram (forcing the timing of the 800mhz stick down). There have also been reports that people have contacted manufacturers for flash roms to flash the sticks with the proper timings, and getting them to work in Penryn units this way.

But the OP doesn't have a Penryn.

There have been numerous reports of people using 2x2GB 800mhz in their pre-penryn, SR MB's and MBP's with no problems.

Which brings us back to the OPs problem. You do have a SR chipset, pre-penryn, so you should be able to address all 4GB actually. When you installed both sticks and got a black screen, was the white light on the front pulsing? Typically that indicates that the sticks were not completely installed.

 

[Luzzio]

You're partly correct. MB's do not "support" 800mhz ram, because the 800mhz FSB is bottlenecked by the speed of the memory controller, which still tops out at 667mhz. However, the memory should automatically downclock to 667mhz and work just fine. This has worked for most all MB's until Penryn, and the theory should hold true for Penryn as well. This said, there has been a problem with some brands of 800mhz ram in Penryn units; SPD values being off, therefore not working in PENRYN MB/MBP's, unless one of the other sticks is Apple ram or 667mhz ram (forcing the timing of the 800mhz stick down). There have also been reports that people have contacted manufacturers for flash roms to flash the sticks with the proper timings, and getting them to work in Penryn units this way.

But the OP doesn't have a Penryn.

There have been numerous reports of people using 2x2GB 800mhz in their pre-penryn, SR MB's and MBP's with no problems.

Which brings us back to the OPs problem. You do have a SR chipset, pre-penryn, so you should be able to address all 4GB actually. When you installed both sticks and got a black screen, was the white light on the front pulsing? Typically that indicates that the sticks were not completely installed.

Yeah, black screen with the front light pulsing, that's what happens when I put in both 2gb cards. I've pushed it in really hard... maybe not hard enough.

Will try again.

 

[CanadaRAM]

They probably don't work because the RAM's SPD values do not have the correct entries for operation at 667 MHz. They theoretically "could" clock down in non-Penryn machines, but they are not properly programmed to do so.

You might find that one of them plus the Apple module in the other slot works -- this is because the machine is reading the timing information from the Apple module. When there are 2 x 800 MHz in there, there is no valid information for the machine to read.

Take the Kingston ValueRAM modules back for a refund, they are never going to work in this machine. Stick with RAM that is guaranteed compatible with your machine.

 

[King Herod]

They just don't like me

At my work I convinced the boss to upgrade our Macs to 4GB of RAM to ease our VM usage (I test quite a bit of things in VMs) and it felt slow with 2GB. Three of our staff are using shiny new 24" iMac's with the 1066 FSB/800mhz Memory and my machine is the slightly older, Mid-2007 Aluminum Santa Rosa iMac. As such I decided to just buy four kits of 2x2GB 800mhz DDR2 SO-DIMMs (PC-6400) and be done with it. Being a Mac and a PC user/support specialist for decades and never having a problem with the faster-than-spec'ed being a problem I figured it would be great....my bad.

The iMac did not like 2x2GB of 800mhz RAM. It works fine with one 2GB and one of the original 1GB 667mhz modules. It does not work with just the known-good, booted fine, 2GB module. After much switching and testing (I had 4 kits remember, I tried a lot of modules in this machine) it appears the machine needs at least one piece of RAM is can read the 667mhz SPD rating on, and then it sets that for both chips. It doesn't matter what slot the 667mhz module is in, it just has to be there.

So, long story long, I am using 3GB right now and contemplating what to do. Processing another order for more RAM is not lots of fun to ask of the boss after he ponied up for 22GB (upgrading our PCs too). I kind of want to throw these modules in a laptop PC and run CPUZ to see what the SPD readout is. Maybe I should just look for a Mac program that gives that info....hrm, bootcamp = pain in my butt...grrr...loaner Montevina laptops appear to be DDR3, argh!