New Mac Pro slower with extra memory. Why?

Got my new mac pro 2.8 octo with standard 2GB memory last week and its brilliant. Really pleased.

Just put in 4 x 2GB memory from OWC (slots 1,2 top card and slots 1,2 bottom card) and it is now slower when I use my 3D app Strata CX 5.5. Strata is a 32 bit app so it has a 4GB limit, but when doing a test render activity monitor shows only 350-400MB real memory being used and a whopping 1.4 GB virtual memory being used.

Does anybody have any ideas as to why the real memory isn't being used instead of the slower virtual memory. Is it the app or the OS that controls this?

I wasn't expecting massive gains in render speed, (it's quick enough as it is), but its an expensive way to slow your machine down.

I have been advised that the more memory you put in the larger the OS overhead, is this the case?

I am hoping the 10.5.2 update might help but I'm not hopeful. Is anyone else finding their machines slowing down?

 

The 1GB sticks aren't in there. 2 x 2GB top card and 2 x 2GB bottom card, 8GB total. A couple of other threads have mentioned to leave out the stock memory because its unbalanced if you fill 6 slots instead of 4 or all 8. I just hope when I buy another 8GB it doesn't slow down even more !!!!

 

Memory purchased is OWC Mac Pro Qualified.

Just talked to Apple Tech Support and they are puzzled and have asked me to try different memory configurations to see it changes anything.

 

Okay, just finished some test renderings, so here are the figures.

The software I am using is Strata CX 5.5, a 3d modeling and render package similar to C4D, Lightwave and Maya etc. I am rendering a single frame image of a large restaurant with about 75 light sources. There are no start up items and Strata is the only app running apart from activity monitor to check memory and CPU usage. Memory as I mentioned before is OWC qualified.

Render 1
Stock 2 x 1GB (Apple)
Slot 1 top card
Slot 1 bottom card
Real memory used 1.7GB
Time - 1h 35m 5 s

Render 2
2 x 2GB slots 1 & 2 top card (OWC)
2 x 2GB slots 1 & 2 bottom card (OWC)
Real memory used 2.43GB
Time - 1h 31m 56s

Render 3
2 x 2GB, slots 1 & 2 top card (OWC)
2 x 2GB, slots 1 & 2 bottom card (OWC)
2 x 1GB, slots 3 & 4 top card (Apple)
Time - 1h 31m 46s

It seems that if I do a more simple render there is an actual slowdown with the greater amount of memory installed ie 10m 39s instead of 10m 25s. Once you start to push the machine it does slightly better, but I don't consider a saving of 3/4 mins on a 90min render impressive.

The only thing I have noticed is that running other apps such as Safari or Camino with Strata in the back ground don't seem to suffer and are just as snappy as if they were running on there own.

If I do any other times I'll publish them in this thread.