Raid and Audio!!
The Problems with Sata and Raid for audio recording.
There are TWO reasons why you need to be careful when using SATA for audio, below I will discuss them both in easy to understand terms.
Some boards which add SATA support are doing so by adding the controller into the motherboard via a virtual pci slot, whereas a standard IDE port that we are used to using, bypass's the pci bus all together and are integrated in to what's called the South-bridge chipset. The standard IDE has its own bus which is much faster than the pci bus and does not have to share its bandwidth with lots of other devices. With something as important as audio to be stored and retrieved in a timely fashion without any hickups, sharing a bus is what can make or break the pc. Some of the better boards have SATA controllers off the pci bus on their own dedicated bus, these are the boards to use. Fortunately more boards are getting safe built in SATA controllers then when this article was first written but a lot of boards are still having problems.
Koutech PIR133 Raid PCI Card (great PCI card for Raid) interferred with PCI bus / audio latency causing glitches / audio freezing. Removal of the card solved pblms. Increasing buffer size helped as well.
Imagine the pci bus like a 4 lane highway. If your audio-card takes up 2 lanes with its traffic, the sata takes up 3 lanes and on top of this you have a network card, modem, scsi ect ect. Something is not going to work properly when the highway gets congested. As audio is so important to be delivered on time its the one which suffers the most, ie you get clicks and pops. With low latency you don't have a big buffer to allow for the times when the pci bus is congested, because the sound-card suffers from clicks and pops usually the owner of the computer starts blaming the audio cards drivers which is totally wrong.
People for a very long time have recommended a "dedicated pc" and this is the reason why. The more pci cards and built in devices the more congestion you get. Even when your not recording the audio-card is still sending its inputs and outputs across the pci bus, how else would mixers show metering and your monitoring work if it didn't ?
This doesn't mean that if you have one of these cheap sata or raid controllers that you will have problems, its an area that could possibly have a problem and is worth avoiding if audio and low latency is important to you. I wont go into what locking the pci bus is in detail, but this is a separate problem which some of the cheaper sata and raid controllers do to perform better in benchmark tests and hopefully convince people that their brand X sata is the fastest and best one to purchase. If a sata or raid card can stop all traffic so it has all 4 lanes to itself it will perform much faster than if it only had 2 which it has to share with other devices, of course other cards then suffer because they cant use the pci bus. This is caused by the way the driver is written and is technically not caused by the hardware but if its built into the MB then there may only be one driver to choose from in which case your stuck.
Adding a PCI card sata or raid is much better than a cheap built in one as you then have a range of drivers to choose from. Nothing is as good as keeping the hard drive controller off the pci bus altogether. Period.
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