4x1GB verses 2x2GB

[osx-linux]

So, the moral of this story is, according to your diagram and the info you posted, 4x1GB can perform better than 2x2GB+2x512MB? Eventhough you have an extra gig of RAM, most of it is not acting to it's full capacity?

In certain situations, yes.

The 5gigs(in any config) will always, hands down, no questions, absolutely, without a doubt outperform 4gigs(in any config) if you are using more than 4gigs of ram.

The 4x1gb of ram will outperform the 2x2GB+2x512MB of ram if you are using under between 2 and 4gigs of ram, while running a RAM bound application. However, it will offer no measurable performance advantage at all if the task at hand is CPU bound. [At least looking at the two extreme situations.]

The 4x1gb of ram and the 2x2GB+2x512MB of ram will perform nearly identically if you are using under 2gigs of ram.

 

[speekez]

osx-linux

thanks for the extensive explanation. I think that puts things in perspective just enough for me to grasp it, more or less. I can now make an educated buying decision cheers!

 

[joachim]

So in the end, is it advisable to keep the 2x512MB that comes with the base config (assuming I am upgrading to a 4x1GB or a 2x2GB) or sell it off?

 

[osx-linux]

So in the end, is it advisable to keep the 2x512MB that comes with the base config (assuming I am upgrading to a 4x1GB or a 2x2GB) or sell it off?

Installations notes:

4x1GB+2x512mb: install 2x1GB on riser A, lowest slots. install 2x512mb on riser A upper slots. install 2x1GB on riser B, lowest slots. [this will give you 4gigs of full bandwidth ram, nice. plus the extra gig of half-bandwidth if you happen to spill over 4gigs, but less than 5gigs]

2x2G: install 2x2GB on riser A, lowest slots. install 2x512mb on riser B, lower slots. [this will give you 2gigs of full bandwidth ram, plus an extra 3 gigs of half-bandwidth ram.]

--- those installation configs assumed ---
The only benefit with purchasing the 2x2G is that "later" you can go buy another 2x2G for a 4x2G config [8gigs, full bandwith] that still has room to expand upto 16gigs in the future. You do this at the cost of having half-bandwidth ram if you are using over 2gigs untill you go purchase your other 2x2G chips (which I assume you must be doing if you are thinking of upgrading to 8gigs, and even want to leave an 'easy' option for 16gigs.)

With the 4x1G purchase, you still have the ability to go out sometime "later" and purchase 4x2G and sell off the 2x512mb to give you a massive 12gigs RAM, all while having loads of full bandwidth ram all along your upgrade path. The downside here is that in order to upgrade to the full 16gigs you'd have to also sell off your 4x1G ram in order to install that last 4x2G.

The extra RAM will not hurt you, it can only help (albeit at half-bandwidth).

In the 2x2G case, if you sell off that 2x512mb you are shooting yourself in the foot, giving yourself 0 gigs of full bandwidth ram and 4gigs of half-bandwidth ram.

In the 4x1G case, if you sell off that 2x512mb you give yourself 4 gigs of full bandwidth ram. You will have, however, shot yourself in the foot if you will be using over 4 gigs of ram, but under 5 gigs of ram.

All of that being said, if you are know you are going to be using more than 4gigs of ram, do yourself a favor and bite the bullet and go get 4x2G. You'll get 8 gigs of full bandwidth, 1 gig of half bandwidth and plenty of room to grow.

For many people 4 gigs of RAM is 'enough'.

So there ya go. "It depends upon your needs." Hopefully that gives you enough information to decide.

 

[joachim]

osx-linux: excellent explanation!

I wasn't sure if having the 2X512MB on the higher slots would affect the 4x1GB slots, but knowing that 4 gigs would be utilized fully with anything over it be at half bandwidth is much better than anything over using virtual memory.

I'll just be working with the CS3 Design Premium applications, and I'm sure that I won't need more than 4GB at this point, and knowing that I can one day upgrade to 12GB at full bandwidth is more than enough for my needs.

Thank you for your thorough explanation, much appreciated!

 

[Sun Baked]

Personally, I wouldn't worry as much about dual/quad channel operation.

Buy the denser memory, this will give you 2 more memory upgrades before you begin tossing memory.

The machine can handle 32GB of memory (quite likely since the XServe can) -- so you will be adding more in the future.

Eventually you will be sticking some in the drawer, something that'll happen much quicker if you buy memory 4 DIMMs at a time instead of 2 DIMMs at a time.

The biggest performance boost is made by avoiding the VM Manager, the performance boost between dual vs. quad channel operation isn't as big.

 

[mustang_dvs]

So in the end, is it advisable to keep the 2x512MB that comes with the base config (assuming I am upgrading to a 4x1GB or a 2x2GB) or sell it off?

If you order RAM from OWC, they offer a refund if you send them your OEM RAM once your new RAM is installed.

 

[akadmon]

Installations notes:

4x1GB+2x512mb: install 2x1GB on riser A, lowest slots. install 2x512mb on riser A upper slots.

Sorry for asking a potentially stupid question, but what do you mean by lowest and upper? The riser cards horizontal, so I'm a bit confused.

Am I correct in saying that upper = back and lowest=front (looking into the MP from the open side)?

 

[GrBear]

At places like OWC and Datamem, the difference between buying 4x1GB and 2x2GB is fairly minimal.

Macworld did a benchmark test using 2x1gb sticks (matched memory) vs 4x512mb sticks (matched memory). They showed a substantial increase in speed with 4.. so yeah, I would say. I wish I could find the test results again because I wanted to send the link to a friend looking at a Mac Pro. The speed gains where alot higher than the 20% quoted by another poster here.

 

[osx-linux]

Sorry for asking a potentially stupid question, but what do you mean by lowest and upper? The riser cards horizontal, so I'm a bit confused.

Am I correct in saying that upper = back and lowest=front (looking into the MP from the open side)?

lower slots == dimm slots 1 and 2
upper slots == dimm slots 3 and 4

http://manuals.info.apple.com/en/MacPro_MemoryDIMM_DIY.pdf

 

[osx-linux]

Macworld did a benchmark test using 2x1gb sticks (matched memory) vs 4x512mb sticks (matched memory). They showed a substantial increase in speed with 4.. so yeah, I would say. I wish I could find the test results again because I wanted to send the link to a friend looking at a Mac Pro. The speed gains where alot higher than the 20% quoted by another poster here.

I've seen tests like that too. Most likely the results were based upon mem copy tests only (memory read/write speeds alone.) Such tests, I've seen show performance increases of 50% or higher.

The main issue with tests like that is what they mean to 'real world performance', which is what the anandtech article (see earlier in this thread) tried to quantify. What they found was that for memory intensive scenarios the speed up was upto 20%, while (expectedly) for cpu intensive operations the speedup was under 5% or not noticable at all.



Cheers,

 

[GrBear]

I've seen tests like that too. Most likely the results were based upon mem copy tests only (memory read/write speeds alone.) Such tests, I've seen show performance increases of 50% or higher.

I suspect your right. To play it safe while I wait for my Mac Pro to arrive (then I can replace my Wintel Core 2 Duo 2.66GHz boxen) I ordered 2x512MB FB-DIMMs from OWC. With todays modern OSes, I can't fathom anything less than 2 gigs of RAM. It's going to be interesting when I upgrade, I'll likely go with another 4x512MB FB-DIMMs just to ensure full bandwidth for the whole kaboodle.

Thanks for pointing out to put the extra DIMMs on the other riser card, otherwise I would have put it on the card with the existing RAM.

 

[killmoms]

Thanks for pointing out to put the extra DIMMs on the other riser card, otherwise I would have put it on the card with the existing RAM.

Actually, you probably wouldn't have. There's a diagram on the inside of the Mac Pro's removable side-panel that illustrates that it's best to fill in the risers in the order described above.

 

[kitki83]

What is best for my needs

Ok I have the stock 1gig(2x512) setup, and it seems having 4 gigs is the rule of dumb, my question is how will I create the best ram setup,

(in my understanding this should be best setup, correct?)
4x512mb
2x1gig

or

3x1gig
2x512mb

or

2x512mb
1x2gig
1x1gig

Thank You

 

[CanadaRAM]

Ok I have the stock 1gig(2x512) setup, and it seems having 4 gigs is the rule of dumb, my question is how will I create the best ram setup,

(in my understanding this should be best setup, correct?)
4x512mb
2x1gig

or

3x1gig
2x512mb

or

2x512mb
1x2gig
1x1gig

Thank You

You can't do odd numbers, RAM MUST be installed in pairs.

I would choose either 4 x 1 Gb or 2 x 2 Gb. I can't see the point in purchasing 512 Mb modules.

 

[kitki83]

So its best to sell stock ram and buy 4x1gig set?

 

[juanm]

My opinion is that it is extremely foolish to purchase anything but two 2GB sticks at a time for $430 at Omni Tech via Ramseeker.com. Everyone charges more and there is nothing wrong with what Omni Tech sells at all. Buy 4GB at a time two x 2GB sticks for only $430 at Omni please. And no I am not affiliated with Omni in any way.

I don't want to start a war, but c'mon...

http://www.resellerratings.com/store/Omni_Technologies

It only costs between $50 and $70 more on OWC... http://www.resellerratings.com/store/Other_World_Computing_10

And with a little google you can probably find more good deals...

 

[Zwhaler]

Personally, i think it will be a rare individual who will need 16GB of RAM in the next 2 years, even among Ocho buyers.

Off topic, I know, but what's funny about that post (assuming "Ocho" was a typo) it works both ways because Ocho means 8 in Spanish. Lol

 

[Sun Baked]

So its best to sell stock ram and buy 4x1gig set?

No, it is best to buy the biggest pair of DIMMs you can afford and add those.

The performance boost between 4x1GB and (stock RAM + 2x2GB) won't be as noticeable as just adding another 4GB of RAM -- unless you have an app that requires a lot of RAM bandwidth vs. as much RAM as you can get.

If you don't have enough RAM, the VM manager slows down to a HD speed of 75MB/s vs. 10GB/s for actual RAM.

Quad channel is more of an ego boost than a productivity boost.

 

[BiikeMike]

I just got my Mac Pro yesterday, stuck with the 1gig of RAM. My plan, after reading this thread is to get 4x1gig sticks, put those in one riser, and put the 2x512s in the other riser.

If I am understanding correctly, this will give me 4 gigs of fully optimized RAM and 1 gig of not so fully optimized. Is this correct? someone tell me quick, I'm about to hit order

 

[killmoms]

I just got my Mac Pro yesterday, stuck with the 1gig of RAM. My plan, after reading this thread is to get 4x1gig sticks, put those in one riser, and put the 2x512s in the other riser.

If I am understanding correctly, this will give me 4 gigs of fully optimized RAM and 1 gig of not so fully optimized. Is this correct? someone tell me quick, I'm about to hit order

No. That's not right. You need to put 2x1GB sticks in slots 0 and 1 of riser A, then the other 2x1GB sticks in slots 0 and 1 of riser B. Then put the 2x512MB of RAM in slots 2 and 3 of riser A. That'll get you 4GB of optimized RAM and 1GB of not-fully optimized.

 

[BiikeMike]

No. That's not right. You need to put 2x1GB sticks in slots 0 and 1 of riser A, then the other 2x1GB sticks in slots 0 and 1 of riser B. Then put the 2x512MB of RAM in slots 2 and 3 of riser A. That'll get you 4GB of optimized RAM and 1GB of not-fully optimized.

Yeah, thats what I meant to say

Thanks

I figure this is the best route for me, because if in the future I need more RAM I can start buying 2GB sticks, and I don't think i'll EVER need more than 12GB. And if that time ever comes, it'll be way down the road when I have the new 32-core Mac SuperDuperPro!

 

[spaz8]

If you order RAM from OWC, they offer a refund if you send them your OEM RAM once your new RAM is installed.

Could u point me to where on the OWC site it says that about the OEM ram discount.. since ive been wondering what to do with the Apple 2x512mb.. if i get the 4x2gb OWC..

add it to the end and have 9gb's but at a slight performance hit.. or get some money back.

 

[BiikeMike]

Could u point me to where on the OWC site it says that about the OEM ram discount.. since ive been wondering what to do with the Apple 2x512mb.. if i get the 4x2gb OWC..

add it to the end and have 9gb's but at a slight performance hit.. or get some money back.

http://eshop.macsales.com/money-back-rebate/mac-pro-xeon-memory#macpro

$75!

 

[akadmon]

Could u point me to where on the OWC site it says that about the OEM ram discount.. since ive been wondering what to do with the Apple 2x512mb.. if i get the 4x2gb OWC..

add it to the end and have 9gb's but at a slight performance hit.. or get some money back.

Hold on to the 2x512MB Apple sticks! You will be sorry when you have to have your MP serviced under warranty, because Apple will not do anything unless there is at least 1 MB of original RAM in the machine.