There should never be (i'd say, will never be, but someone might complain) any glitches on rendering no matter how many renders you do simultaneously and how low power your computer is. Theoretically you could perform thousands of simultaneous renders with a 33MHz 486DX without a single glitch. It would just take forever or longer ;). Of course, a faster processor will get the job done faster, but you don't need a fast processor to do simultaneous renders. Remember, rendering is NOT a real-time operation like capture or print-to-tape. It will take as long as it takes with no glitches or dropped frames, ever.

How much memory? Well, more will help. Make a guess that each Vegas session needs some, perhaps 32MB or so (i really don't know, this is purely a guess). If you have more Vegas sessions running than you have room for in RAM they will have to start swapping out to the hard drive as Windows switches between the sessions. I've run a dozen simulataneous renders in 256MB of RAM without any noticeable swapping so Vegas' RAM needs are probably very modest.

... and will the cache on the CPU have any influence? I mean, will there be a difference if you use a 3.2 P4 1 Mb cache compared to a 3.2 P4 512 cache?
And what about L1 and L2 ??? I don't quite get it now...
Is it more usefull for the overall job a comp' is doing?

Larger and better cache will always help. However, the original question was what is necessary, not what is helpful. True, whatever will make the job faster is a good thing, but you can do multiple simulaneous renders on something very old and slow. This isn't a task that is only possible with the latest and greatest hardware.

"Theoretically you could perform thousands of simultaneous renders with a 33MHz 486DX without a single glitch. It would just take forever or longer ;)." this not correct, the address space of the 486dx is very limited, xp will not function correctly, windows2000, nt, can only serve a limited number of tasks! system overhead exceeds available time, task time tables can not be maintained, IO starts to have buffer over run.

As Chienworks was stating, Vegas is a great NLE. and functions nicely with multi copies of itself in memory. One must remember when rendering that vegas uses other programs for inputing images, QT,.... 100 still tga for task1, 30 stills jpeg for task2, .. the problem becomes how many copies of a support program can exist in memory at one time and function correctly or not create vast delays because of unique resources or just lock up.

multi rendering is nice, but batch jobs are the way to go.

How about do an experiment on your system. Prepare several representative 1 minute clips and render them individually. Them render multiple sessions. Probably will take about the same clock time running them sequentially as concurrently.

While you're doing this, open up "Task Manager" and look at the Performance tab. If one render session has CPU at 100%, then don't expect to see much improvement in total time running more than one concurrently.

Depending on the video (straight cuts with little FX, for example) you may find that the bottle neck is the CPU or perhaps the disk drive. Sometimes my CPU is 60% utilized, and at others it is 100%. Depends on the video.

Let us hear what you find.

OdieInAz, nicely stated!

Tygrus,

You should not need a double processor to do this.

I have done three renders to wmv at once with P4 2.66 and 1 gig of ram.

Also you may want to look at the vegas Batch Render script. You can line up all your projects to render and it just goes one after the other. Sometimes that is a better workflow. Particularly, if you want to be render in one instance and editing in the other.