DDR2 800 in penryn Macbook Pros?

wolfattack

macrumors member
Original poster
Feb 27, 2008
76
0
I was just wondering if the new macbook pro's will take DDR800 ram? Or does it max out at 667 still?
 

DocSmitty

macrumors regular
Jan 7, 2008
237
0
Lincoln, NE
DDR2 800 worked in previous revision MBPs just fine. So, that's what I bought for my Penryn. For whatever reason, it does NOT work in Penryn MBP. Be warned!!! (it's not just bad ram, others have had this issue)
 

spaceballl

macrumors 68030
Nov 2, 2003
2,856
240
San Francisco, CA
Some of the info on this thread is incorrect.

Fact: DDR2 800mhz RAM WILL work in a DDR2 667mhz slot JUST FINE. They are pin compatible. The only difference is that the DDR2 800 RAM is tested and rated for a higher speed. The RAM speed in a computer is determined by the motherboard chipset though, not the RAM. So running it at 667mhz is perfectly fine. (i.e. driving a car rated for 70mph at 60mph is fine. But if your car is only tested to go 70mph, best not run it at 80!)

More Important Fact: There are many different RAM settings such as CAS latency, timing delays, etc that are also tested and spec'd, but most retailers don't advertise that stuff unless you look closely and dig for it. And even if you find it, Apple doesn't really publicly state what memory specs are needed for their laptops in this regard as they'd rather just sell you the memory themselves.

Most Important Fact: Apple computers are historically very finicky about which memory they like and which they don't. If you go to an online store with a good reputation in the mac community, you might pay a bit more than if you went to the cheapest place on pricewatch/pricegrabber/ebay, but you usually get some kind of guarantee. This is the best way, imho, to protect yourself and get good memory.

Hope that advice is useful for some out there!
 

rezonat0r

macrumors 6502
Nov 2, 2007
398
0
Plenty of people have DDR2-800 memory working fine. Anytime you add memory I would highly recommend running a real memory diagnostic. Something like memtest86 which is included on the Ultimate Boot CD.
 

CanadaRAM

macrumors G5
The problem is that there is no advantage at all to installing DDR2-800, AND if the SPDs are not written correctly on the RAM, it won't downshift to 667 properly, so there will be problems. We are getting reports that 800s that work in the SR MBP do not work in the Penryn. The SPD setings control the RAM module's identity, and what speeds, voltages and latencies it will work at.

In the past, the problem has come up because a new model (or new firmware rev) enforces the standards more strictly, and RAM that is slightly off-standard gets gonged.
 

DocSmitty

macrumors regular
Jan 7, 2008
237
0
Lincoln, NE
Some of the info on this thread is incorrect.

Fact: DDR2 800mhz RAM WILL work in a DDR2 667mhz slot JUST FINE. They are pin compatible. The only difference is that the DDR2 800 RAM is tested and rated for a higher speed. The RAM speed in a computer is determined by the motherboard chipset though, not the RAM. So running it at 667mhz is perfectly fine. (i.e. driving a car rated for 70mph at 60mph is fine. But if your car is only tested to go 70mph, best not run it at 80!)
Yes, some of the info in this thread IS incorrect ;)

Sadly, both physicistjedi and I have tried our pc2-6400 RAM and it does not work. I'm willing to believe CanadaRAM's explanation of why, as I have never dived that deeply into RAM firmware.

The TESTED FACTS are:

PC2-6400 WORKED in Merom SR MBPs
PC2-6400 DOES NOT WORK in Penryn SR MBPs.

I understand that you are advising people to buy RAM guaranteed to work with their Mac, and I agree. Just wanted to state that in this case, 667 and 800 are not compatible.
 

spaceballl

macrumors 68030
Nov 2, 2003
2,856
240
San Francisco, CA
The TESTED FACTS are:

PC2-6400 WORKED in Merom SR MBPs
PC2-6400 DOES NOT WORK in Penryn SR MBPs.

I understand that you are advising people to buy RAM guaranteed to work with their Mac, and I agree. Just wanted to state that in this case, 667 and 800 are not compatible.
Once again, please see my second point about how there are things OTHER than just the rated memory speeds that affect compatibility. I have no problem believing that your testing yielded the results that you posted - but this is not because of the fact that it is ddr2 800.
 

spaceballl

macrumors 68030
Nov 2, 2003
2,856
240
San Francisco, CA
and RAM that is slightly off-standard gets gonged.
yup - that's why just pay like 5 to 10 percent more and grab some RAM from a place that has good results in the mac community. I've been burned by trying to save a few bucks by getting cheap RAM elsewhere and I def regretted that.
 

rezonat0r

macrumors 6502
Nov 2, 2007
398
0
Can people please post the actual specs of the memory that doesn't work in terms of latency (e.g 2-2-2-6 or 3-3-3-8 or 4-4-4-12). The problem is likely from a mismatched pair than from anything else. I don't have a Penryn MBP yet, but if I did I would run memtest86 and post the memory specs it reports for the stock memory here.

Apple has possibly begun using a slightly different spec'd memory (hopefully higher than lower :rolleyes:) in the Penryn models. It has already been proven that a mismatched memory pair can affect performance, and a certain amount of mismatched-ness apparently now causes real problems.

So again please post actual specs of the memory that comes with Penryn systems, and the specs of memory that does not work alongside the stock module.
 

DocSmitty

macrumors regular
Jan 7, 2008
237
0
Lincoln, NE
It's not an issue of running the new ram along side a stock module - the people I've seen with pc2-6400 bought matched pairs. For further info, the ones I had that did not work were 5-5-5-15, which is pretty much the standard currently.

All of their timing and latency specs matched up - I believe it's the inability of the logic board to downclock it that is causing problems.
 

DocSmitty

macrumors regular
Jan 7, 2008
237
0
Lincoln, NE
Then explain why the ram works just fine in a pre-penryn mbp and not in a penryn mbp? It's clearly some change in the laptop itself, not the RAM.

Edit: I went to the mfg's site before school and viewed the data sheets on the RAM. the voltage, cas timing, etc, all identical. I'll try to post links.
 

spaceballl

macrumors 68030
Nov 2, 2003
2,856
240
San Francisco, CA
Then explain why the ram works just fine in a pre-penryn mbp and not in a penryn mbp? It's clearly some change in the laptop itself, not the RAM.

Edit: I went to the mfg's site before school and viewed the data sheets on the RAM. the voltage, cas timing, etc, all identical. I'll try to post links.
Most likely because the newer laptop run a different CAS/tRCD/tRPD/tRAS setting that your memory SODIMM can't handle. Has nothing to do w/ the fact that it's DDR2 800. Apple is pretty mysterious about what their timings settings are or when they decide to change them. moral of the story: just get RAM from a seller that guarantees it to work in the mac.