Mid 2009 Macbook Pro. Can/should I use only 1x8Gb RAM leaving the other slot empty.

Basically what happened is that I had seen around that Macbok pros, though Apple said they could only accept 8Gb, could actually accept 16. So I went ahead and ordered 2x8Gb modules. I now realize that this is on 2011 and later models. Is there anything inherently wrong with operating with only one module (ie. using one of the 8Gb modules and leaving the other port empty) or should I only use pairs of RAM (2x4Gb)?
I ask because I got a great price on the RAM and would end up paying the same for 2x4Gb as I did for the 2x8Gb but would end up with an extra 8Gb module for a rainy day if I stuck with the RAM I bought.
If I shouldn't use only one at a time, is there a reason why? What (very) limited knowledge I have of computer hardware makes me think that the fewer the better, but I could very well be wrong and if I am I'm curious why. I'm always happy to learn things.

You will be fine. It doesn't HURT anything. There is a theoretical minor performance enhancement to using 2 modules, but unless you are engaging in activities where you need to extract absolutely, positively, every possible ounce of performance out of your machine (in which case, you should buy a new machine), it's not worth worrying about.

Fuzzy_Buzzard said:

Basically what happened is that I had seen around that Macbok pros, though Apple said they could only accept 8Gb, could actually accept 16. So I went ahead and ordered 2x8Gb modules. I now realize that this is on 2011 and later models.

Is there anything inherently wrong with operating with only one module (ie. using one of the 8Gb modules and leaving the other port empty) or should I only use pairs of RAM (2x4Gb)?

I ask because I got a great price on the RAM and would end up paying the same for 2x4Gb as I did for the 2x8Gb but would end up with an extra 8Gb module for a rainy day if I stuck with the RAM I bought.
If I shouldn't use only one at a time, is there a reason why? What (very) limited knowledge I have of computer hardware makes me think that the fewer the better, but I could very well be wrong and if I am I'm curious why. I'm always happy to learn things.

Click to expand...

If you have a mid-2009 MacBook Pro...I'm not so sure this is going to work. The mid-2009 MBP has a true max. ram of 8gig...which means 2 x 4gig ram sticks. If each slot could address 8gig sticks of ram...then it would probably have a true max ram of 16gig (which it doesn't).

I would also suspect that the 8gig stick of ram that was purchased may not even be the correct ram for the computer...it may not even fit because of the pin configuration if it's the wrong ram.

The great price on the ram may also indicate that it's the wrong ram. Usually newer ram is less expensive than older ram (ram for 2011 MBP's vs. ram for 2009 MBP's).

Give it a try...maybe we will all learn something!

- Nick

If it was a 'great' price as Nick suggests it is probably not Mac compatible. Macs require low density memory, not the cheaper high density modules most PC's use. Check out OWC and Crucial, the recommended Mac suppliers. Select your model and check out prices:-

http://eshop.macsales.com/shop/memory/Apple_MacBook_MacBook_Pro/Upgrade

And almost all modern computers use a dual channel memory controller to speed up access to memory - incl'g all modern Macs - some, like my homebuilt Win box use a triple channel memory controller. Basically, what this does, while one stick of memory is being used for a process, the other stick is being made ready for the next process. It requires 2 identical sticks of RAM for the memory controller to function properly and do it's job. Without these 2 identical sticks you are slowing down the process of memory usage on your machine.

Assuming Nick is correct (since I didn't go look it up) and 8 GB is the max RAM on your Mac, it's probably not going to boot with a single 8 GB stick, but you can give it a go - and assuming it is the correct type of RAM. The only thing that will happen is that it won't boot.

Thanks for the replies guys, but I should note that this RAM was purchased specifically for a Mac from Newegg in the Apple compatible section. Off the top of my head I think it was 204 pin, 1333GHz, DDR3. Regardless, I don't think that will be an issue. Also, nothing but good reviews for the RAM so I don't think it should be an issue of quality either.

I did not know about the dual channel memory control though. I will give it a try to see what happens with only one stick but luckily I know many people with the newer Macbook who would be happy to have this RAM so I shouldn't have any problem selling it.

Is there any way for me to check if it uses a dual channel memory, even if it works only with one stick? If it ends up being slower with 1x8Gb I would rather sell the pair and buy 2x4Gb. From what I have seen in my research, people have had problems where one of the slots died but the computer still functioned only with half the RAM so I am assuming it will accept only one.

Are there any other issues inherent with using only one?

Oh and I should note that it is enroute to me and I don't actually have it yet. I will happily update this thread once I see what happens.

Fuzzy_Buzzard said:

Thanks for the replies guys, but I should note that this RAM was purchased specifically for a Mac from Newegg in the Apple compatible section.

Click to expand...

While this all may be true...there are many many different Apple Macintosh computer models...and there are many diferent types of ram used in Macintosh computers.

Fuzzy_Buzzard said:

Off the top of my head I think it was 204 pin, 1333GHz, DDR3.

Click to expand...

As I mentioned in one of my earlier posts...I suspected that the incorrect ram was purchased...since to the best of my knowledge...Mid-2009 MacBook Pro's really do not support 8gig sticks of ram.

Mid-2009 MacBook Pro's need 1066 MHz PC3-8500 DDR3 SDRAM...not what was purchased.

FYI...when you do not know exactly what ram an Apple computer needs...it's best to visit site's like:

- OWC
- Crucial.com

...since they have very detailed ram info pages or a "ram finder" system that will correcty identify what ram you need. Once you know exactly what ram you need...then you can purchase it from the website you desire.

- Nick

Mid-2009 MacBook Pro's need 1066 MHz PC3-8500 DDR3 SDRAM...not what was purchased.

Click to expand...

Ah, I see where I went wrong. From here: MacBook Pro "Core 2 Duo" 2.53 13" (SD/FW) Specs (Mid-2009 13", MB991LL/A, MacBookPro5,5, A1278, 2326*) @ EveryMac.com
I read that the "Min. RAM speed" was 1066 MHz (not GHz as I said earlier... bit of a difference) and as a result thought that I just couldn't go lower but could potentially go higher. I realize I should have made sure before I went ahead with this.

Anyways, no harm done as the package isn't here yet so I can just refuse the package for a full refund. I appreciate your help.

pigoo3 said:

While this all may be true...there are many many different Apple Macintosh computer models...and there are many diferent types of ram used in Macintosh computers.



As I mentioned in one of my earlier posts...I suspected that the incorrect ram was purchased...since to the best of my knowledge...Mid-2009 MacBook Pro's really do not support 8gig sticks of ram.

Mid-2009 MacBook Pro's need 1066 MHz PC3-8500 DDR3 SDRAM...not what was purchased.

FYI...when you do not know exactly what ram an Apple computer needs...it's best to visit site's like:

- OWC
- Crucial.com

...since they have very detailed ram info pages or a "ram finder" system that will correcty identify what ram you need. Once you know exactly what ram you need...then you can purchase it from the website you desire.

- Nick

Click to expand...

Alright so I found some that I think will work, I just want to run it by you if that's okay so I don't have to go through this again.
Newegg.ca - Mushkin Enhanced 8GB (2 x 4GB) DDR3 1066 (PC3 8500) Dual Channel Kit Memory for Apple Model 976644A
Should be good?
Thanks again for all your help.

Fuzzy_Buzzard said:

Alright so I found some that I think will work, I just want to run it by you if that's okay so I don't have to go through this again.
Newegg.ca - Mushkin Enhanced 8GB (2 x 4GB) DDR3 1066 (PC3 8500) Dual Channel Kit Memory for Apple Model 976644A
Should be good?
Thanks again for all your help.

Click to expand...

It looks like the correct ram. And man...that's a very good price!

- Nick