This is my best understanding of how this works. I think you will not want to go higher than 1 GB.

Dynamic Ram Preview is the amount of RAM set aside for the temporary RAM renders of small selected regions during editing. This setting has some effect on final rendering of a project, some of it negative.

You have 2 GB physical ram. You have set aside 1GB for RAM preview. So when your page file hits 1 GB in used size, Windows starts using your hard disk to swap between physical and hard disk space. This is the point where I have noticed CPU dropping even down to zero, the cpu waiting for the memory to catch up.

I think when it's not set to zero, Vegas is doing extra things that make no difference on the final render output, in otherwords, 40% of that 100% is doing unnecessary things. When set to zero, it is concentrating on the task at hand, rendering your final project.

You can do this next item if you dare (you need a solid machine with good cooling). In XP Task Manager on the process list, you can see programs and their current cpu percentage. Right click the vegas program in the list and you can change the Windows priority. I use "HIGH" sometimes, never "REAL TIME". Don't expect to do anything else with the machine until the render completes, though.

I don't think you will reach 100% cpu all of the time, simply because Windows does a lot of background things. I can write a program that sucks up all of the cpu and gets things done quickly, but people won't want to use it because it locks the machine up.

Also don't forget the list of programs/components involved: Windows, Vegas, Plugins, RAM, Hard Disk, WMV codec.

I have an AMD 4600+ X2 with the default setting of 16 on the ram with 4 gig total ram and during the render the processor is nailed between about 95 and 100%. It is basically almost straight line at 100%.

JJK

Same experience for me as JJKizak.

PIV 2GHz and 2.6GHz PCs, both with Vegas, rendering to DV or MPEG-2-DVD-profile give 100% pretty well through the hole process for me too. I'd expect less only when the source is being read down a transfer cable that is too slow to get the data through quick enough. Not that I'm bragging about realtime rendering - rarely ever do I get that.

I'm just happy to get back to the editor in the morning and not be stuck at 99% completed. Which has happened a few times when rendering out - sometimes requiring a repeat render, sometimes 99% is when checked actually 100% to the last frame/field.

Do you have any effects, color correction, generated media? I agree that most of the time with DV mine is pegged at 100%. I've been working mostly in HDV lately, that is where I see a lot more variation in CPU usage.

Just a quick update to add to the mystery...

I haven't made any tweaks or changed anything...

Today I rendered the exact same file to a DV AVI file (as opposed to WMV yesterday)....

The PF went up to 1.3GB and leveled off, and both cores of the CPU stayed at 100% throughout the render...

Hmmm...

- Ben

I noticed a few issues about vegas and x2's. The avi renders uses the x2 well, but WMV renders vary alot. WMV performance and the OS management appears to be more tightly tied together in the MS way. A light XP Pro and a XP media center are worlds apart in rendering WMV speeds, with the light XP Pro being the winner.

Filmy links should be a great help in getting more out of OS. There has been other threads on the vegas forum about extra disks, temp files, swap files, 3d track motion performance issues and general "gotcha" issues in vegas that should help.

That reminds me. May be of no consequence:
Dual core CPUs from both Intel and AMD have had a quirk in Windows that might need plugging. The inactivity assessment that is made for the power save mode can slow down both processors when, for a period of time, one CPU has been running idle. So even if one of the CPU cores is running along quite active, if the other core is almost idle, the OS can be incorrectly instructed to command a slowdown of all CPU clocks. However, this may not be the case in this instance. If you are using a desktop, and you don't feel the need to ever be environmentally sound, you could, as a workaround, turn relevant power saving features off in the BIOS (motherboard setup) and in Windows. In case this has any influence on the problem that appeared before. Once a slowdown has occured, both CPUs would need a demand above a certain level to encourage a speed-up of the system back to normal levels. Assuming you don't yet have a fix for this installed.

Only other consideration might be delay caused by a highly fragmented file system or a drive that is approaching failure that is spending lengthy amounts of time doing repair-attempt housekeeping.

This is a really good point but you have to wonder...if one core is idle and the cpu gets clocked down to save power wouldn't the other core still be running at 100%, but in the clocked down state? Yes, the CPU could be going into power saving mode but even if it were I'll bet that isn't the primary issue here.

Ben, you say that at 0MB for prerender the CPU runs around 60%. What you don't give is a comparison of the render times. I'm curious to know if the CPUs run at 60% AND if the render is actually faster, or comparable to the render with a 1.0GB RAM Preview allocation.

Ram preview memory is used for your previews to RAM and I think also for general caching. Vegas normally does a smart cache of frames in an attempt to boost subsequent preview passes. This is why your preview usually improves if you allow a region to play in a loop. Vegas caches occasional frames until the preview reaches full speed.

I probably sound like a broken record here 'cause I've said this many times, but setting your RAM Preview very high in Vegas 6.0 seems to force Windows to start writing parts of Vegas to the page file. This will slow down your performance and possibly raise your CPU usage if you hit a "sour spot" that forces the CPU to get busy handling the page file while rendering. On a system with slower rendering you might find that the render keeps pace with the disc performance, on a faster system you might find you are constantly reading and writing the page file.

The moral here is to open up your task manager and watch what happens to the page file under different RAM preview settings. You might find that lower is better for general vegas usage. And you might find that a setting of 0 is best for final renders even though the CPUs are sitting at 60%. You just have to test.

I'm sure some codecs make better user of dual processors than other codecs so you might find that some types of renders never get those dual cores up above 60%/core.

Finally, I'm sure you've looked at temperature and CPU monitors since you're overclocking your machine. Renders usually peg a CPU at 100% for quite a while which gives you greater potential for overheating, so it's something to keep a close eye on.

Rob Mack

1) The Videoguys tweak guide linked above is very 90's and erroneous. The IoPageLockLimit registry entry was no longer referenced in Windows after Windows 2000 SP1. It is not in XP or Serverf 2003. Don't waste your time.

The other Videoguys tweaks will have limited value, or likely to cause slow downs of programs starts and shutdowns etc. You can always disable file indexing later if indexing happens while you need to do some big rendering.

None of those Videoguys tweaks will do anything for CPU utilization issues in Vegas.

2) Also, the Windows dual-core cpu bug only impacts a small percentage of users and has to do with powernow issues. Highly unlikely this is related to any Vegas isssues. If anything, that bug would cause CPU utilization to rise as they run at a reduced power level.

It is quite difficult to program for multi CPU support. Code has to be re-written and added to support both single-CPU and multiprocessor users. I think some of Vegas 6.0 may have been updated to provide improved multi cpu support, but it's not that robust yet compared to something like Cinema 4D's products.

I have spent a lot of time watching the CPU optimization patterns in Vegas. I recently did a lot of testing while trying to render a project on two network renderers. Here is what I think:

(My workstation is dual Opteron 252 CPU's with RAID arrays 4-GB RAM, not dual core. The renderers are a non-RAID dual-core 3800+ X2 2GB RAM, and a non-RAID P4 2.8Ghz Northwood 2 GB RAM.)

1) Vegas 6 does indeed provide improved dual-cpu and dual-core cpu support primarily for the Sonic Foundry DV Codec. Both my dual CPU and dual-core computers render Sonic Foundry DV Codec AVI files with constant 100% CPU utilization.

2) Rendering to HDV .AVI (uses the cineform codec) drops CPU utilization down to 60 - 80% range on both dual-core and dual-CPU computers. The single CPU P4 system runs at 100% cpu utilization.

3) Rendering/encoding to DVDA NTSC Widescreen MPEG (MC codec) utilizes 100% CPU on all three systems very well.

2) Rendering to MPEG HDV (MC codec) drops the dual-core and dual-CPU computers down to 70 to 80% CPU utilization. The single core P4 runs at 100% cpu utilization.

A couple of notes. The decreased CPU utilization on multi-processor computers appears to be Vegas application and/or codec related, not at all related to hard disk or memory bandwidth bottlenecks or tweaking optimization. Every time someone posts about this Vegas multiprocessor performance inefficiency, it seems that people are inclined to reply with suggestions to upgrade disks or memory.

Fact is this is an issue with the Vegas code. I hope more people post about this and provide examples of tests and findings. This should help the Vegas developers further improve multiprocessor support in subsequent releases of the product. Denial will get us nowhere. "=)

Peter, I'd have to agree with your findings...

The DV codec seems to work well with dual CPUs, whereas teh .wmv seems less optimzed.

I can only guess that the RAM preview at 1GB allows the .wmv codec to perform at 100% for at least a short while, until it requires the usage of the pagefile.

- Ben

Ok guys, so help me out on this one. I set my dynamic preview to 0 megs and the CPU stayed around 50-60% during render. Then I put my dynamic preview to 16 megs and the CPU used went up to
100% during render, so which one is better?

Does having windows xp home on a dual core machine, make a difference in CPU utilization?

The more processor usage the better. That means that Vegas is doing it's job faster.*

I'm not an authority on this topic, but i believe i've heard that XP Home doesn't make use of dual cores or dual processors.

*I have to laugh very long and loudly about this one. Only a couple of years ago many folks were complaining about the SonicFoundry programs taking up nearly 100% of the processor cycles!!!! *gasp* Why was that a bad thing?