Athlon 64 Memory Limitations?

I've been running an athlon64 3800+ with two sticks of DDR400 512MB each, and just grabbed another pair of DDR400 512MB to go up to 2GB. When I put in the 2 new DIMMs and booted up I noticed that my RAM is running at 161.2 (CPU/15) instead of 200 (CPU/12).

I called both Corsair and AMD and both told me that, its a limitation on the memory controller of the AMD Athlon 64 chip, where if you put 4 chips in instead of 2, its going to downclock your memory.

Checking online I was reading something about any revision e chip (my chips revision is dh-e6), was supposed to fix some issue having to do with decreased performance with 4 DIMMs, but I can't find anything about 4 DIMMs downclocking the memory.

I'm just curious what the real technical limitations are here, and if I should just manually kick up my ram back to 200. Any help with this issue or explaining it a little bit better than the AMD/Corsair guys did would be greatly appreciated.

Edit: My chip IS a Venice core, which should have the new improved memory controller.

Four sticks never work as well as two.

I believe there is something called memory map rehole or something, and i remember reading once it was for large amounts of memory, ill check when i get a chance to reboot my machine...

Venice is a stepping E1 or E2 it has the improved controller. Your BIOS may not be able to determine a matched set of parameters from the SPD chips on all four dimms to run at 800. Be sure they are socketed for dual channel with matched dimms. Set the timings manual and voltages as needed using the Lats from the slower of the two sets.

Make sure you're running 2T command rate... and as Cajun said, set your timings manually.