Installing DDR2 6400 instead of DDR2 5300?

californiak

macrumors newbie
Original poster
Aug 29, 2007
8
0
Just got late 2008 17" MB pro and was wondering if i could install 2x4GB DDR2 PC2-6400 800MHZ 200pin Laptop SODIMM instead of the 5300.... read somewhere that you can push the limit little higher with the RAM on these... any ideas out there? like to get at least 6GB of RAM working... it says front bus is 800Mhz so the 6400 should work?

thanks, Mike

Model Name: 17" MacBook Pro
Model Identifier: MacBookPro4,1
Processor Name: Intel Core 2 Duo
Processor Speed: 2.5 GHz
Number of Processors: 1
Total Number of Cores: 2
L2 Cache: 6 MB
Memory: 4 GB
Bus Speed: 800 MHz
Boot ROM Version: MBP41.00C1.B03
SMC Version (system): 1.28f3
NVIDIA GeForce 8600M GT 512 MB,
LION
500GB HD
 

snaky69

macrumors 603
Mar 14, 2008
5,903
480
If it boots, the RAM will downclock itself to the computer's speed. I wouldn't waste my money.
 

dusk007

macrumors 68040
Dec 5, 2009
3,383
61
DDR 800 is still very much standard speed. I am quite sure it is supported. The 200Mhz base clock stuff was never a problem.

Core 2 Duo is 64bit, the OS is 64bit unless the 2008 had still some logic board problem or hard limit that didn't support anything past 4GB there is on reason why 8GB shouldn't work.

It won't be 6GB. Either all 8 work or just 4. Check out what the spec sheet on apple's homepage says about the max supported ram.
 

Ccrew

macrumors 68020
Feb 28, 2011
2,035
3
It won't be 6GB. Either all 8 work or just 4. Check out what the spec sheet on apple's homepage says about the max supported ram.
Apple supports 4. It'll see 6. That's all it will see. It's a chipset limitation.
 

drambuie

macrumors 6502a
Feb 16, 2010
751
0
If it runs in your MBP at 800MHz, the 800MHz will have a better system bus to memory bus ratio. For PC2-5300, or 667MHz RAM, the memory bus speed will be 667/2, or 333MHz. With an 800MHz FSB the FSB to memory ratio will be 8:3. With 800MHz RAM the memory bus will be 400MHz, which means a ratio of 2:1, which equals better FSB to memory synchronization.

However, there is a downside. The PC2-6400 RAM will have a greater latency than the 5300 RAM, which could offset some of the speed gain of the higher speed RAM.

One thing I can't figure out is the 2.5GHz CPU speed. With an 800MHz FSB, it should be 2.4 or 2.6GHz. The CPU clock is 1/4 of the FSB, or 200MHz, so 2.5GHz would require a mutiplier of 12.5.
 

californiak

macrumors newbie
Original poster
Aug 29, 2007
8
0
Thanks for all the info

Thank you all for the info... the reason I want to try it is because my wife has black MB and I would install one of the 2gig boards in her MB so she would get 3gb RAM and I would replace the two in my 17 MBP with the 2 4Gb 6400 boards... I know its little expensive but gaining 50% more RAM ( going to 6 Gigs if it works) would be worth it.... or I could go with 4+2 (6400) little cheaper but apple recommends same in both slots.... so I dont know.

Definitely don't want to mix 5300 (2Gb) and 6400 (4Gb) because of the different speeds. I don't think that would be good.

I believe I have 6GB in my Mac Mini even tho it only shows 4 in About this Mac info.... how can I tell what I have for sure? Anyone knows? Seem to remember reading somewhere how you can tell but dont remember where, lol...

thanks again, mike
 

californiak

macrumors newbie
Original poster
Aug 29, 2007
8
0
So I installed 64GB torqx SSD in my wifes MB and 4gb RAM and is lightning fast... what a difference... and contrary to Apple info 4GB memory on Late 2006 MB works fine....

I also ordered 120GB Patriot SSD for my 17"MBP and I'm getting either 6 or 8 Gigs DDR2 6400 for it...

let you know how it works


mike