Recording - March 2013 - 26

To do this test, use a known CPU-heavy effects-processing plugin, such as a reverb, and stack eight of them up on a basic audio
channel with the wet level set very low. (Make sure the track is
playing audio, as some newer DAWs will conserve CPU by disabling plug-ins and tracks that are not processing audio at all.)
By setting the wet levels low, you still have a track that’s listenable
so you can more easily tell if you have any pops or clicks in playback. Keep doing this until each CPU core hits maximum and
overloads, or until audio crackles start to happen. From here,
off one instance of
plug-in,
6 Of Audio Interfaces, Connectivity, and CPU Loads back the project, and start thedo addisave
to
For the most part, there are three distinct interface types tional tweaking to the system to see if
for audio these days: PCI/PCIe, FireWire and USB.
it provides meaningful results.
PCI/PCIe: While there are relatively few PCIe
My current DAW build can take
audio cards, this is far and away my favorite inter- me up to 100% load, with the graphface. It usually just works with minimal overhead on ics update painfully slow but the
the system compared to its FireWire and USB coun- audio still processing just fine. Your
terparts. Well-written drivers in conjunction with PCI DAW might only be able to handle
cards have provided extremely low latency with 80% CPU load before it chokes, or
buffers set as low as 64 samples for many years. even less. You’ll need to determine
However, modern machines provide few, if any, PCI what is acceptable for you. From
or PCIe slots any more. You’ll also need to make sure experience, it is fully possible to
other cards don’t block the slots you need to use.
build a DAW that will go right up to
USB: USB interfaces for DAWs are by far the most the edge of CPU power and still perpopular today. With USB 2.0 there is enough band- form audio flawlessly with little to no
Another power-saving technique width (60 MB/sec theoretically, 30–40 MB/sec real- tweaking. However, this is the time to
that should be turned off is under the istically) for audio, even for multitracking. USB3 pro8
USB ports themselves. Sometimes the vides significantly more bandwidth (theoretically
ports go to sleep and the device on 600MB/sec) but audio interfaces with USB3 conthe other end doesn’t recover when nections are not available, although there are a few
being woken up or doesn’t do it con- USB 2 interfaces that have been certified for reliable
sistently. To turn this off, go to Start use on USB 3 ports.
Menu > Control Panel > Device
However, just as I’ve experienced with several
Manager > Universal Serial Bus USB interfaces, CPU load for processing the same
Controllers > USB Root Hub > plug-in is higher on the exact same project, time and
Properties > Power Management tab time again. Another point of consideration, espeand uncheck Allow the computer to cially with laptops, is this: Are there enough ports in
turn off this device to save power. the right spots on the chassis to support every USB
You’ll need to do this for all the USB device you need to use? Some devices might parRoot Hub devices. See Figure 7.
tially block the adjacent USB port, rendering them
useless for your needs.
FireWire: Falling out of favor over the last few
The Final Test
years, the FireWire interface has its issues with make sure it performs as you want it
As you breathe that big sigh of respect to Windows. One of them is finding a com- to. If you’re going to have problems,
relief now that audio is playing back patible chipset that works with your audio interface of this is the time when they are most
smoothly, there is one additional test choice. Audio interface makers specifiy using a Texas likely going to be exposed. If everyand many
posted
to this point,
7 Instrument chipset, about their musicians have non TI- thing checks out OK uplikely be OK
to Internet forums
struggles with
congratulations, you’ll
based FireWire ports. Dedicated DAW builders also for the foreseeable future.
build their machines with TI-based FireWire ports.
Another issue with FireWire: Just like USB, it uses
system resources just to be running, with no audio Conclusion
Getting that perfect audio machine
load. On my i7 950 3.06 GHz quad-core machine,
once I launch my host, I notice one of my cores can be no picnic. Even if you buy a
already bouncing with 0–20% CPU load right off the CPU that you know to have plenty of
top. While I have a ton of headroom to spare, and power, that doesn’t mean things will
I honestly haven’t run out of CPU grunt to finish a go smoothly. The build-your-own
song I’m working on, it is one more thing to think method requires time, inclination,
technical aptitude, and confidence to
about when choosing an interface.
Now we wait for USB3 and Thunderbolt audio pull it off. Having one of the established DAW builders build a rig for
interfaces...!
you is a valid alternative.
I recommend that I do for all my reviews. Create a test project
While you could easily buy an IBM, HP, Dell, etc. at one of
that will max out every processor core up to 100% CPU usage. the big box stores, if you run into issues, I promise you’ll get litTo be sure of an accurate CPU reading, it’s best to do this from tle support for your DPC spikes or other plug-in related woes.
Task Manager (see Figure 8) and check the Performance tab, This is why I suggest checking the return policy if you decide to
rather than rely on a CPU usage meter inside of your host.
take this route. So be prepared to spend some time doing your
The CPU Usage History graphs above will show every core homework to figure out what will work best for you.
and its workload.
May luck be on your side!
26

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Recording - March 2013

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