R3D rendering: More than 8gb useful?

[Jochen Schmidt-Hambrock]

I´m planning to get a new Nehalem 2,66 GHz 8core Mac Pro.

For R3D rendering does it make sense to order more than 8 gb?
Or do I run into an I/O bottleneck before I´m using the 8 gig?

I have a Fusion DX800 raid system (680mb/sec read; 700mb write transfer).

Is there already an expert opinion?

Jochen

[Josh Negrin]

until snow leopard comes out, all programs are running in 32bit mode. This means one program will only utilize a maximum of 3gb. But, with that said, I'm running 11gb on my mac pro. Looking forward to snow leopard!

[Antoine Baumann]

until snow leopard comes out, all programs are running in 32bit mode.

This is simply not true!

OSX leopard is able to run 64bit application and use all the ram you have. Maxon Cinema4D is one example.
When OSX snow leopard will come out, there will be only a slight difference, it will a true 64bit os but still able to run 32bit and 64bit apps. You will only see your ram taken if the applications is 64bit or if has some ram management like after effects.

Now for redcine, well scratch is still 32bit so I won't count on redcine before seeing scratch be 64bit, but I might be wrong. And for redalert, well, somebody from red could tell us if it is something that will happen.

The thing to understand is that it is not your os that will make your apps 64bit, you really need the whole chain: cpu, os and applications.

And as said, as long as dev software company don't make UI using cocao instead of carbon (even fcp 6 is written with carbon) you won't see many 64bit applications under osx.

cheers,
antoine.

[Uli Plank]

REDrushes is much faster with more RAM, it likes at least 2 GB per core.

[RivaiC]

decoding is using CPU. How do you see redrushes being faster with more RAM ?

[Jochen Schmidt-Hambrock]

So more RAM makes no difference? Will there be no noticable speed increase between 8 and 16 gig for rendering r3ds?

And another thing is the triple channel mode: Is ist better to have 12 instead of 16 gig?
6 instead of 8?

Cheers, Jochen

[Dominic Jones]

Without a doubt the best bet is to use all of the memory channels (i.e. fill the expansion boards with chips) regardless of the amount of RAM you're installing.

Of course, the downside to this is that if you want to expand the RAM at a later date, you've got to pull out a bunch of smaller chips. So for my tuppenceworth, especially seeing how cheap RAM is at the moment, get enough to see you through a sensible lifespan for the machine, in chip sizes that fill your available slots...

HTH,
Dom.