latency issues

28 May 2010 03:18 #3030 by chuck1024
latency issues was created by chuck1024
I have been using a M7SUA mother board with a 2.4Gig Athlon. I used the integrated video system with decent results. Latency was about 12k for normal things but, I could get high numbers in the 48k range only if I ran a specific game or opened movie player. I ran emc using a 12k for a long time without any problems.

Today I bought and installed a diablotek ATI Radeon 9000 64MB PCI video card expecting to see better latency. I was surprised to see that in general it got worse. It is now very easy to get 20-25k numbers by opening a firefox window or a PDF file. Worst case is still about 48k with movie player.

Overall system performance is much better. Web stuff is faster and opening PDF files is faster.

My BIOS firmware is pretty old (2004) and a new version (2009) is available. Will it make any difference?

I chose this card because I read a comment that "In general old ATI cards work well". I thought this was an old one.
FYI, I am running a Prolight 1000 mill and I have the max speed set to 60IPM.
Any suggestions?


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02 Jun 2010 03:51 - 02 Jun 2010 03:52 #3062 by mware
Replied by mware on topic Re:latency issues
The integrated graphics uses the AGP bus to access the cpu. The parallel port and many other devices use the pci bus. You added a better video card but it is now using the pci bus bandwidth and taking bandwidth away from other devices, mainly the parallel port.

The cpu does a round-robin polling on the pci devices, it contacts each device and asks if it needs anything. If the device needs something the cpu processes the info then moves on to the next device... After adding the pci video card it now has to contact the video card each time in addition to the other devices and the video card always needs something done. The purpose of the agp bus was to resolve this exact issue, it allows the video card to directly access the cpu without wasting cycles on the pci bus.

I am new to EMC but have alot of hardware experience and I've seen this issue alot when people try to run pci video cards, the video card always takes priority and the sound skips...

Switch back to the onboard, if you want to decrease the latency disable unused devices in the bios. disabling the onboard sound and serial ports would help. And if you have any other pci cards that are not used, like a modem, take it out completely.

If your motherboard had an AGP slot and you used an AGP video card it might have given you the result you were looking for, the latency might not have dropped, but it wouldn't have increased, and you would have had better video performance.

Your options are:

swap the motherboard and video card for ones that use an agp slot,

upgrade the entire system....

or switch it back to the way it was and keep using it, and optimize it by disabling unused devices.

Last edit: 02 Jun 2010 03:52 by mware.

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