Preload Buffers, Buffer Size and Latency

[cgrafx]

What is the relationship between Preload Buffers, Buffer Size and latency?

For example... is the latency of the system for a 2x32 setting the same as a 1x64 setting?

[Bob L]

Almost...

It is actually the number of preload buffers plus 1 times the buffer size... plus whatever latency is in your converters.

So... 1 x 64 means there is one buffer of 64 samples up front that must come thru first before any data can be processed... therefore one blank buffer goes out... then another blank buffer goes out while that data is processed... then that buffer goes out... so the latency is 2 x 64 samples.

So 2 x 64 is not quite the same as 1 x 128 because the extra buffer up front is now twice as big.

Bob L

[cgrafx]

thanks bob.

I have been running 2x32 in our studio with no slipped buffers.

My live SAC system however is having problems at 2x32 but seems stable at 1x64.

I'm trying to sort though the live rig to determine what may be stomping on the SAC engine, but in the mean time I can run the system at 1x64.

This is a dual core i5. I've already tried single cpu and the various priority settings along with disabling one of the cores. So far its still slipping at the lower buffer setting.

[Bob L]

Make sure the HyperThreading is turned OFF in the BIOS... that makes things look like 4 cores... when you look at the task manager performance tab you should see only two graphs... not four.

Another thing could be the video card... are you using internal video... an external card... what kind... nVidea cards can stomp on everything at a low level since it seems their primary objective is to win video gamer graphics performance tests... try another video card..

Be aware... even cards from the same manufacturer can cause problems from one model series to the next.

For instance... the last machine I built started out with an ATI 5450 video card... testing the machine with a load of only 2% slipped 20 to 30 buffers everytime I used an F-Key... completely useless... I checked everything... nothing worked... I was about to change out the mother and start over, when I decided to try another video card I have used in many previous systems... the ATI 4550 HD... less money even... problem completely gone... no slipped buffers pushing the system to 99% load... and playing the F-Keys like a piano player.

Assume nothing... this stuff borders on the twilight zone sometimes.

Bob L

[cgrafx]

Make sure the HyperThreading is turned OFF in the BIOS... that makes things look like 4 cores... when you look at the task manager performance tab you should see only two graphs... not four.

Another thing could be the video card... are you using internal video... an external card... what kind... nVidea cards can stomp on everything at a low level since it seems their primary objective is to win video gamer graphics performance tests... try another video card..

Be aware... even cards from the same manufacturer can cause problems from one model series to the next.

For instance... the last machine I built started out with an ATI 5450 video card... testing the machine with a load of only 2% slipped 20 to 30 buffers everytime I used an F-Key... completely useless... I checked everything... nothing worked... I was about to change out the mother and start over, when I decided to try another video card I have used in many previous systems... the ATI 4550 HD... less money even... problem completely gone... no slipped buffers pushing the system to 99% load... and playing the F-Keys like a piano player.

Assume nothing... this stuff borders on the twilight zone sometimes.

Bob L

Hi Bob,

Yes.. hyperThreading is off.

Not sure what I can do about the Video card issue, as I'm using the built-in Video on the Core i5.

Guess I can try adding an actual card and see what happens.

There may be some video settings I can adjust.

pg

[gdougherty]

Not sure why it hasn't before, but it occurs to me that the onboard graphics would be using shared memory access. I'd expect video access to main system memory, especially on a CPU with the GPU built-in, would temporarily hog memory access and possibly stomp on SAC's access causing essentially the same problems as a multi-core setup.

[905shmick]

Make sure all power saving options are off in the BIOS such as C1E and CPU thermal control.

[Butch Bos]

I am using an I5 and the on board graphics with no problems at all. I can run 2/32 and no slipped buffers. Its an Asus mother board.

Butch

[cgrafx]

I am using an I5 and the on board graphics with no problems at all. I can run 2/32 and no slipped buffers. Its an Asus mother board.

Butch

Hi Butch,

Thats good to hear. I haven't had time to fully assess the issue I'm having. I did remove some start-up processes that are not needed and am seeing an improvement, but still dropping buffers. Its worse when using SAC Remote.

I was going to try over clocking the system to 3.6 GHz (its 3.2 native) and see if that is enough to eliminate the buffer issue.

[gdougherty]

3.2GHz shouldn't even be necessary for stable dropless operation. Overclocking won't help, you've got something else going on. The thought that it's worse with SACRemote makes me suspect networking. Right-click My Computer, choose Manage and select the Device Manager. Under the View Menu, look at Resources by Type, expand the IRQ listing and look for what's sharing IRQ with the audio interface. If you can, try disabling the other devices on the same IRQ. You also may want to make sure your BIOS is up to date if you haven't already.