Dynamic RAM preview determines how much RAM Vegas sets asides for quick, temporary previews of the final effect (you press Shift-B to activate it for the current selection). It has nothing to do with how much RAM Vegas can access for its operations outside of this one feature.

If you don't use dynamic RAM preview or don't even know what it is, you can actually reduce this setting to 128 or 256 (which is what I would recommend) so that Vegas can use the extra RAM for its other features.

Good advice.

The one thing I'd add is that Vegas, in addition to ram previews via <SHIFT+B>, uses the ram preview memory to squirrel away frames as it plays so that subsequent plays will be a little better. It caches frames.

It's generally better to use modest settings as John recommends. A setting that's too high can cause problems for Vegas.

As far as memory usage goes, the simplified info is that
--32bit XP and Vista (and Linux and anything else 32-bit) can only really access about 3.2GB of memory even if you have 4GB installed. This is a limitation of the hardware architecture, not the OS.
--32bit XP and Vista allow applications to use up to 2 GB of virtual address space. This is not the same as physical RAM but is a combination of RAM and page file.
--There are exceptions that can allow an application to use 3GB if it is built to do so. Vegas is not, but it can be hacked to do so at your own peril.
--A 64-bit version of XP or Vista can adress more than 3.2 GB.

Rob Mack

Rob - actually, your first statement is incorrect - 32bit OS is typically the limiting factor - not the hardware.

Cliff Etzel - Solo Video Journalist
bluprojekt | SoloVJ.com

It depends on how you're looking at it. The BIOS assigns addresses to hardware other than DIMMS starting at 4.0GB and then filling downwards. Then it looks at the DIMMS and starts assigning addresses from 0 on up. If the system isn't 64-bit capable then it just doesn't assign addresses to RAM if they've already been assigned to other hardware.

If the system is 64-bit capable then it starts assigning addresses above 4GB to the remaining RAM. However, a 32bit OS can't see those addresses above 4GB. You could view this as an OS issue but it's not specific to 32-bit Windows.

The part where it becomes clearly an architectural issue is that the BIOS assigns the range around ~3.2GB to 4GB to non memory hardware before an OS is ever even loaded, so that range is gone, gone, gone even if you use a 64-bit OS.

Hypothetically, if you use a motherboard with a hard limit of 8GB, load it to the max with RAM, and use a 64-bit OS, you'd find that you can only address about 7.2 GB. The issue hasn't changed.

In truth, though, several chipsets that are supposed to be limited to 8GB actually support more. The specs have been published this way to jive with the fact that you can only install 8 GB in most systems. 4GB DIMMs aren't on the market yet but, afaik, they work and some chipsets actually support more memory than the published specs claim. Meaning that you'll actually get you full 8GB.

Rob

We've got a stack of SuperMicro rack mount servers, both Xeons and AMDs. Most of them have 8 or 12 2GB sticks in them for 16 or 24GB of RAM. No problems with any of them. 'Course, we spent about $3000 to $4500 each for them.

Oh, and of course, they don't run Windows.

That's super but we're getting way out of the realm of what G Media needs to know.

Vegas is configured to try to limit your ram preview settings to a sane number. Since G Media has so much memory available setting the preview high shouldn't be too much trouble but he might find a happpier medium setting it a little lower.

A lot of this will probably change when the 64-bit version ships.

Rob

Ok look its Friday really don’t wont to think about heavy stuff right now just tell me who do we blame?

"Dynamic RAM preview determines how much RAM Vegas sets asides for quick, temporary previews of the final effect (you press Shift-B to activate it for the current selection)."

Geez... you learn something new every day. I never knew about SHIFT-B, but I suppose if I ever sat down and actually read the manual.... NAH! That's too much like work.... and I'm a man... I don't need a manual!

"Ok look its Friday really don’t wont to think about heavy stuff right now just tell me who do we blame?"

----------------------------------------------------

Blame Bush. Duh.

The messenger, of course!

;-)

Rob

It's also listed right there on the menu. No need for the manual this time.

Rob

Now, Now. Skilled professionals went to a lot of work to design it this way. That pretty much leaves him and his party blameless.

;-)

Rob

SHIFT-B .. very useful. Never knew about it either. BUT.......

I seem to remember that Dynamic Ram Preview does have an effect on rendering times. My recollection is that the higher the RAM, the slower the render. I think that some people think the opposite is true. I had my Dynamic Ram set to 128k but probably would like to have more for SHIFT-B -- and yet, if I go to 1024, it will slow down renders.. At least it slows down using John Cline's Rendertest-hdv ------ as I recall anything above 256 starts to slow down rendering.
Don't know why --- might be wrong --- mostly relying on memory here and two runs of the rendertest just now seem to bear it out.

I seem to remember that Dynamic Ram Preview does have an effect on rendering times.There have been dozens of tests and hundreds of posts on this over the years, and I think you are correct. However, the underlying code changed several times as Vegas evolved, and I don't think the impact on render times is consistent from one version of Vegas to the next. So, if you are interested in pursuing this, you'll have to do your own tests with your version of Vegas. To do this test, render a 5-15 second segment to whatever format (MPEG-2) you use the most. Throw out that result, because all subsequent renders will be from RAM (because Windows caches files up to the amount of free RAM). Then, render a second time and note the render time. Write down the RAM preview setting.

Then change the RAM preview setting, quit and restart Vegas (I think you have to do this after changing RAM preview, but I can't remember) and repeat the test. Do this for at least 0, 64, 128, and 256. You can try 512 and 1024. Should take five minutes or less for you to do the whole thing.