[dmegatool]

Does the RAM is that much superior ? I mean... it's really expensive. Is it worth it ?

Can I wait and see a 3rd party makes RAM as good as apple one ? ...less expensive ?

[MCQ]

Apple RAM is always overpriced.

That said, there's not too many options available for FB-Dimms.

http://www.newegg.com/Product/Produc...ubCategory=147

[dmegatool]

I dont know that much about RAM.

Is this pretty similar ?
http://www.newegg.com/Product/Produc...82E16820134085

Edit : Apple's RAM is 240 pin ? (I repeat : I dont know that much about RAM.)

[dmegatool]

Forgot to ask ...

I'm targeting 4gb of RAM. Macpro comes with 2x512.

Will it be faster if I remove thoses and put 4x1gb. Or 2x2gb is it faster. Or 3x1gb+2x512 will be fine ? ...

[ZachPruckowski]

You want dual configs. Or ideally quad-configs because of the way the controllers are set up. 4x1 GB would be the fastest way to do it.

EDIT - by fastest I mean "most bandwidth", not easiest, and not clockspeed.

[dmegatool]

And what about 8x512 ? Can it compare to 4x1gb?

[halfassed]

are you in graphic design, because if you are not stay away from anything more than 2gb otherwise it will kill your preformance

[chucker]

Originally Posted by halfassed are you in graphic design, because if you are not stay away from anything more than 2gb otherwise it will kill your preformance

More RAM will kill performance?

[dmegatool]

hehe. Yeah I'm in. Photoshop and 3dsmax (will have to boot in windows, noooooooooo. Maybe parallels will offer me a good performance but I dont think so)

I just read the documention of apple about adding ram yourself. My only question left is : 8x512 vs 4x1gb?

[Paranoid666au]

http://manuals.info.apple.com/en/Mac...ryDIMM_DIY.pdf

You could use third party RAM though Apple recomend there own.

[Yonzie]

Originally Posted by dmegatool I just read the documention of apple about adding ram yourself. My only question left is : 8x512 vs 4x1gb?

Each stick of RAM is 64-bit wide.
To get maximum bandwith (256-bit) you need 4 sticks.
Anything above that is (from a bandwith perspective) pointless.

[initialsBB]

Originally Posted by MCQ Apple RAM is always overpriced. That said, there's not too many options available for FB-Dimms. http://www.newegg.com/Product/Produc...ubCategory=147

as far as i can see both the Kingston and the Crucial RAM on that page are made up of 72 modules per DIMM... the apple spec sheets specify maximum 32 modules per DIMM.

i can't find 32 module FB-DIMM DDR2 PC2 5300 anywhere...

apart from that, i've read good reviews of FB-DIMM DDR2. negative point is that for the moment almost no-one is making them, being that they are destined for "mission critical servers", but most manufacturers have announced products.

[dmegatool]

Originally Posted by Yonzie Each stick of RAM is 64-bit wide. To get maximum bandwith (256-bit) you need 4 sticks. Anything above that is (from a bandwith perspective) pointless.

Ok... nice. But that doesn't tell me wich is the best. 8x512 or 4x1gb ? "One 4sticks" or "a pair of 4sticks"

[Mugge]

Originally Posted by dmegatool Ok... nice. But that doesn't tell me wich is the best. 8x512 or 4x1gb ? "One 4sticks" or "a pair of 4sticks"

Yonzie has already explained this, but here's how I would put it:

Four sticks: 4*64bit=256bit
Eight sticks: 8*64bit=512bit

Since the memory bus is "only" 256 bit wide you need four sticks to use all your bus' potential bandwidth. If you put in more than four sticks you will get more memory, but not more bandwidth. So using 8*512MB sticks will give you 4 GB RAM @ 256 bit, because the bus can't cope with 512 bit. But it doesn't hurt performance, it just means that those last 4 sticks wont increase your memory bandwidth from 256 to 512 bit.

You should see it from an economical perspective instead; what is the cheapest? 8*512 MB sticks, or 4*1 GB sticks, keeping in mind you only have 8 slots and you might wish to upgrade at a later time.

[dmegatool]

Thx Mugge. That was the kind of explanation I was waiting for !!! (kinda noob with RAM stuff)

And about the memory riser card, why there is 2 of them ? Because 8 sticks couldn't fit on a single one ?

Like when Muggle said "Since the memory bus is only 256 bit wide" I though it was 256 per riser card.

[MacConvert]

Originally Posted by halfassed are you in graphic design, because if you are not stay away from anything more than 2gb otherwise it will kill your preformance

Please explain. I'm on an old mac -- runing 512MB RAM. I was contemplating 4GB RAM on a Mac Pro because I used a Quad G5 at an Apple Store with 4GB that really smoked on all of the paces I put it through.

I can only really afford 2GB RAM on one of these, and even that is pushing it. I'm asking you to explain, because it might make me feel easier about not finding the extra money to put into getting 4GB.

[Kickaha]

Yeah, uh, halfassed, I'm interested in hearing the explanation behind this one too... I'll be gentle this time...

[torifile]

I'm thinking it's something he heard a long time ago and still believes to be true. Just like any drive over 120 gb gets wasted because the OS can't read more than 120 gb.

[Kickaha]

Heh. Hey, he was gracious in the other thread, I'm interested in hearing what he's got to say on this one. You get used to a *LOT* of weird crap as a Windows user.

[initialsBB]

Originally Posted by initialsBB i can't find 32 module FB-DIMM DDR2 PC2 5300 anywhere...

anyone found some third party RAM ? is this 32 module story complete bull ??

[Eugene]

Just be aware that FB-DIMMs from Apple will have heatsinks designed specifically for the cooling system and aftermarket RAM will not.

[initialsBB]

i'm aware of that and anyways it's entirely possible to find these things to stick on, but on page 2 of this technote it states :

DIMMs for Mac Pro must fit these specifications:
667 MHz, FB-DIMMs
72-bit wide, 240-pin modules
36 devices maximum per DIMM
Error-correcting code (ECC)

i know i made a mistake above saying it was 32 modules but, duh, it's 36... question remains the same however.

[spotcatbug]

Heat sinks on RAM modules? Has anybody ever heard of these being required in any PC before? Are these modules a totally new type? I never even knew heatsinks for RAM modules existed before the Mac Pro was unveiled.

[Bryson]

On that subject, I just took a detailed look at the temperature monitor on my Quad, and the RAM is the hottest part. I guess the time for a heatsink on Ram has come.

[initialsBB]

Originally Posted by spotcatbug Has anybody ever heard of these being required in any PC before?

well there's me for a start.
i haven't personally ever used them but i know of others who have, including G5 owners who like Bryson noticed that it is a part of the tower that heated up more, so they took precautions. they're pretty cheap so it's not that big a deal.

[LudwigVan]

Found this on MacWorld's site:

Does the Mac Pro use the same RAM as other Intel Macs? No. While the DDR2 RAM in the Mac Pro is the same speed as that in all other current Intel Macs (667MHz, compared to the Power Mac G5’s 533MHz), the Mac Pro uses Fully Buffered Memory modules, or FB-DIMMs. Each FB-DIMM has built-in error checking and correction, and carries a chip (known as an Advanced Memory Buffer, or AMB) that controls data transmission. As a result of the AMB chip on every RAM module, each Mac Pro DIMM comes complete with its own heat sink. Apple says that by attaching a heat sink to every module in order to dissipate heat, it can keep fan noise to a minimum. Apple says it’s provided a thermal specification for the modules to the companies that are manufacturing Apple-branded RAM for these systems. (Since they can come from different manufacturers, RAM modules may vary in appearance depending on how their manufacturer chose to meet Apple’s specs.) Apple’s also pushing for its thermal specification to be adopted as a standard by the JEDEC standards body, which would make it easier for third-party RAM vendors to manufacture heat-sinked RAM to meet the needs of Mac Pro users. How do I install RAM in the Mac Pro? The Mac Pro has two small riser cards, each of which contains four FB-DIMM slots. To install RAM, you slide a riser card out and set it down on a flat surface. (The bottom of the riser card contains plastic feet so that the circuit board itself doesn’t make contact with the surface to place it on.) Then you install the memory modules—always in pairs of the same capacity from the same manufacturer. You need to install pairs of RAM in the proper order, which is printed on the inside of the G5 door: a pair in the top two slots of the top riser, then in the top two slots of the bottom riser; then in the bottom two slots of the top riser; and finally in the bottom two slots of the bottom riser. When you’re done installing RAM, you slide the riser card or cards back into the Mac Pro until they re-connect with the motherboard. Apple includes two 512MB modules in the stock configuration. As with the Power Mac, the Mac Pro requires matched pairs of RAM to function. To max out the RAM, you’d need to install 2GB modules in each of the Mac Pro’s eight RAM slots. That’s a lot of RAM.

[brutox]

These guys have a kit of 2x512 with the heat sink for $199 http://omnitechnologies.biz

[Yonzie]

Originally Posted by initialsBB DIMMs for Mac Pro must fit these specifications: 667 MHz, FB-DIMMs 72-bit wide, 240-pin modules 36 devices maximum per DIMM Error-correcting code (ECC) i know i made a mistake above saying it was 32 modules but, duh, it's 36... question remains the same however.

On a "normal" stick of RAM, you have 8 memory chips ("devices"), each transmitting one byte for a total of 64 bits. On ECC memory, there's 9 memory chips making them 72 bit wide. The extra byte is used to check the validity of the other 8 chips' data.

In order to double capacity without resorting to higher-capacity chips, the factory can put 8 (or 9) chips on each side of the memory stick, thereby cramming 16 (or 18) chips on a stick.

In servers, with their usually larger requirements for memory, you can also find memory sticks that have two memory chips on top of each other, a bit like a double-decker bus, thereby facilitating 32 chips on a stick of RAM (or 36 with ECC).
The memory controller obviously needs to be capable of "reading" the 16 extra chips, or you'll waste half the capacity of the stick of RAM... I am not aware of sticks that are stacked 4 chips high on both sides, but they might be out there (or arrive at some point in the future) and they won't work properly in your new Mac Pro.

The number of rows of chips (8 or 9 chips in a row) is called "rank".
The Mac Pro supports single- dual- and quad-rank memory modules.

[Eugene]

Already been said in the thread, but I'll simplify it. To utilize the maximum 21 GBps memory bandwidth, merely installing a pair of FB-DIMMs isn't enough. You need a minimum of FOUR FB-DIMMs, a pair in each riser to fully saturate the quad-channel memory bus.

[Res]

Originally Posted by spotcatbug Heat sinks on RAM modules? Has anybody ever heard of these being required in any PC before? Are these modules a totally new type? I never even knew heatsinks for RAM modules existed before the Mac Pro was unveiled.

Heat sinks on ram modules have been available for years -- a lot of the high performance ram used by over-clockers have them.