[EricTheRed]

I visited CompUSA tonight to purchase more RAM for the 3.0 GHz Mac Pro I have on order.

The sales guys first tried to sell me PC5300 non FB-DIMMs but on the advice on this board I refused. Then they sold me Centon RAM.

Get this the specs are: FB-DIMM DDR2-667 PC2-5400. The packaging claims it is "Made for Mac Pro" and shows a stylized picture of a Mac Pro. The RAM has big, black heat sinks. But its part number is 1GBKITFBDIMMG5.

I cannot find this ram on centon.com or CompUSA's web site. I find different ram with the same part number on COMP USA's web site.

I'm now confused. I thought Mac Pros took PC5300, no?

Clue me in if you can. Thanks!

[mduell]

It's a marketing gimmic.

A 64 bit bus at 667Mhz comes out to 5336 million bytes per second. The majority of the industry decided to call this PC2-5300. A few companies (3 that I can think of, mostly catering to the "I've got a window and neon lights" crowd) decided to one-up everyone else and call it PC2-5400.

I'd run memtest86 for a few days to see if Centon is any good.

[EricTheRed]

Originally Posted by mduell 

It's a marketing gimmic.

A 64 bit bus at 667Mhz comes out to 5336 million bytes per second. The majority of the industry decided to call this PC2-5300. A few companies (3 that I can think of, mostly catering to the "I've got a window and neon lights" crowd) decided to one-up everyone else and call it PC2-5400.

I'd run memtest86 for a few days to see if Centon is any good.

mduell,

Thank you ever so much for cluing me in. After I spoke to the folks at Centon who couldn't tell me anything about the RAM because it wasn't in there computer system I lost all confidence so I will return this RAM. As a result of this, I did some shopping on the web about found reasonably priced RAM (although they do have an upcharge to get the Apple recommended heat sinks).

I ended up purchasing two 1 GB (2x512) kits to fill four RAM slots as I've been informed that Mac Pros run faster with slots of four filled. Using all available RAM slots, my new Mac Pro will now have 4 GB of RAM total that I imagine should be enough for what I'll use it for.

Thanks again,

EricTheRed

[mduell]

Filling all 8 slots with 4GB is a bad idea for a couple reasons. The most obvious is that you can't add memory capacity without removing the existing modules; 4GB is a lot today, but it won't be in 2 years. Also the two memory slots that are farther out from the logic board on each memory card have higher latency (at least 3-5ns, which at today's clockspeeds is over ten cycles), and FB-DIMMs are already looking at relatively high latency compared to vanilla DDR2. I'd go with 4x1GB (plus the stock pair of 512s in the slots further out) or even 2x2GB if you see yourself adding more RAM in the next year or two.

edit: Wait, did you buy 2GB (4x512) from Apple? I'd drop that back to 1GB if you can still change your order.

[EricTheRed]

Originally Posted by mduell 

Filling all 8 slots with 4GB is a bad idea for a couple reasons. The most obvious is that you can't add memory capacity without removing the existing modules; 4GB is a lot today, but it won't be in 2 years. Also the two memory slots that are farther out from the logic board on each memory card have higher latency (at least 3-5ns, which at today's clockspeeds is over ten cycles), and FB-DIMMs are already looking at relatively high latency compared to vanilla DDR2. I'd go with 4x1GB (plus the stock pair of 512s in the slots further out) or even 2x2GB if you see yourself adding more RAM in the next year or two.

edit: Wait, did you buy 2GB (4x512) from Apple? I'd drop that back to 1GB if you can still change your order.

Again, thank you for the information.

I purchased a refurbished 3.0 GHz from Apple that came with 2 GB RAM (4x512), 250 GB HDD, 1900XT video, and so on. $3299.00 seemed like a good deal.

[mduell]

Huh, that is a good deal. But latency, future expansion, and price all favor buying 2x1GB ($366) rather than 4x512M (2*$218) from memorytogo.

[EricTheRed]

Originally Posted by mduell 

Huh, that is a good deal. But latency, future expansion, and price all favor buying 2x1GB ($366) rather than 4x512M (2*$218) from memorytogo.

When I placed the order I was under the impression that I should use four slots for best performance. Oh well.