"Monday I received my new Mac Pro 8-Core. Great machine. Very quiet and fast (coming from an G4 867MHZ Quicksilver). One issue that bothers me though. I ordered the Mac Pro with the standard 1GB RAM. I spent additional $ for a 4GB kit from Crucial. I added the new RAM before starting up the system for the first time. System Profiler recognizes the RAM as you can see in the screenshots below. (not updated to 10.4.10 - would that help?)

I moved the stock RAM to Riser Card B for performance purposes. (Dual-Channel memory mode would require like (size) dimms in the other riser, having 512's in one riser and 2GB pairs in another will not enable dual-channel)
Last night the system seemed a little sluggish (I work a lot with Adobe CS2) and I checked Activity Monitor to see how the RAM was allocated using the PPC apps. To my surprise Activity Monitor seems to recognize only 1GB of RAM. (See Screenshot)

I ran AHT (Apple Hardware Test), which recognized all 5GB. (Did all the ram pass the AHT memory test?-Mike) However the AHT system profiler added kind of a serial number next to the stock RAM. There was no such number assigned to the Crucial RAM. I wonder whether the sticks from Crucial are fine or whether I need to tweak the system somehow to take full advantage of the added memory. May be one of your readers with a 8-Core Mac Pro has a solution.
Many thanks.
(It appears that they're installed in accordance with Apple's Mac Pro memory install PDF (no longer online) and normally if ram was not fully seated or had some other problem it would not be recognized in ASP. I asked if the system would boot/run with just the 2GB pair installed, but if all else fails, I'd contact Crucial tech support. He later wrote)
The ram is seated properly. I am just on the phone with their tech support. Seems they are baffled too. He's looking for a supervisor right now who might know more. If that doesn't lead anywhere I'll call Crucial.
-Uli "

I assume those FB-dimms were listed by Crucial as Mac Pro compatible. Apple had a doc earlier this year with different memory kit numbers for 8-core vs. quad-core Mac Pros, but no Mac memory dealer I know could explain why (unless it was some issue with a specific AMB chip on some of their FBdimms).

Tip/Solution: From Uli's later mails:

" ...little update. I have been on the phone with Apple support for 30 minutes. Since the level-1 tech could not help they checked with level-2 techs. They said that this is a known issue and an "Archive and Install" of the OS would solve the problem as the system files are overwritten. Well I did that, but I had still only 1024MB of memory showing. :-(

(He later wrote)
Well, here is the Kicker.
Before I called Crucial, I removed the "previous system" folder from my HDD. Re-booted and made sure that all apps are still working. Checked once more Activity Monitor and ...see below!!

Moral of the story, Move your RAM around (in pairs). Archive and install system.
Who would have thought.
Once again, thanks for your support and a great site. Keep it up.
-Uli "