8GB ram plenty for running Logic 9?

You can do either, although to answer the specific question: Yes, 8 GB is more than adequate to run Logic. But this answer is contingent on what other applications you are running concurrently with Logic.

You can open Activity Monitor and set it to monitor your memory usage like this:

The numbers to watch are thos for Page outs: In particular keep an eye on the number in parentheses. If it goes positive and continues to increase, then you are running out of physical memory and need more for your present level of usage and concurrent applications.

1,1 uses FBDIMMs and quad channel symmetrical memory performance (Apple's name btw).

So yes a pair on each Riser.

In 2008 it changed and using all 8 DIMM slots is ideal.

BTW when I had 4GB and then went to 8GB it gave more room for holding in memory and OS X does use memory to cache files, apps, even pointers to directories and folders as well as for working on data. Even if you do not have page outs. Safari has been a prime example of what it does with more RAM available.

Use the new RAM. The stuff from Amazon is nice and using all the same set IS best policy.

New on A1:2 and whatever else in B1:2

4 or 8 DIMMs is what you want to use. There is small higher latency using 6 or 8.

The Mac Pro comes with two memory riser cards, each with four DIMM slots. With a total of eight slots, you can add up to 16 GB of memory.

Note: DIMMs must be installed in pairs of equal size from the same vendor. For instance, you must not have one or three DIMMs on either riser at any time. Additionally, two DIMMs from different vendors should not be combined and used as a pair.

Other configurations of DIMM pairs are still compatible with Final Cut Studio, but may not achieve the same performance levels as when DIMM pairs are installed on both risers evenly.

https://support.apple.com/kb/TS1957

as happens, did not see your last post but got answered.

what I was going to add, make sure your FBDIMMs stay below 70*C and I alwsys use smcfancontrol to set 3 fans to 850 rpm and used Hardware Monitor.

Those are the new default low rpm, they merely keep the fans from dropping down to their normal 499 and 599 rpm is all to insure a better air flow.

Hardware Monitor is paid version and allows tracking temps over time and I am using now for 10 yrs I guess while there are others this one has always been top notch and accurate on core temps and more features. iStatPro is another. There is free version "Temperature Monitor" also. Just don't use more than one and keep such monitoring to a minimum, they can affect a system as in too many cooks spoil the soup, or get in the way monitor hard drive SMART status. Less is more.

None of the utilities will change the one fan so that is fine and fine with temp monitor.

Some will have three preset profiles and create and set a High Profile w/ 1200 rpm settings if they know they need extra cooling - it is easier to keep cool than to wait and then push more air waiting for the fans to kick up on their own.

When system goes to sleep heat from FBDIMMs and other sources continue to build up for awhile which is why Apple changed the behavior so that fans will kick higher rpm when coming out of sleep to push warm air that had been building up.

Your temps are fine. There tends to be one DIMM slot like A2 I think that tends to be warmest from what I saw and from others. But never got above 68*. At one time I did have some FBDIMMs that were running 72-76 even with extra fan control until I replaced those and with a bit extra rpms in the meantime. $29 for 2x2GB FBDIMMs versus the $300 for 2x512MB or $400 1x1GB 6 yrs ago. Time they changed.

Now to find some open road where you can push Ferrari a little!

There are some who have ventured to pick up a pair of 53xx series and now have 8-cores for shockingly low $200 - the 8-core 3.0GHz once cost $1500 extra.

Best investment as far as it goes for 7 yrs. I think next year this time pick up whatever there is then too, low end will be fine, and get another 8 yrs.

The only closed track I know are the synthetic benchmarks you can try to gauge - or just enjoy how fast and smooth apps open and switch and process data.

Just moving to SATA3 6G SSD was very nice jump. No pole vaulting 17 ft but hey feels like flying! And someone was saying that they wanted to fly X-Plane at higher realistism.