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usb vs pci/pci express performance? Audio Interfaces
Old 21st September 2015
  #1
Gear Nut
 

usb vs pci/pci express performance?

hey guys im in for a new interface and wondering is there in general less noticeable stability and cpu performance with a usb 2.0 interface over pci/pci express? im in need for something only for my pc rig in the studio so performance/stability is a priority but there are more options now adays in usb. I know it differs also between companies but like for example the performance difference between a rme usb device such as ufx and internal card such as aio...thoughts?

Last edited by hollo321; 22nd September 2015 at 11:57 AM..
Old 23rd September 2015
  #2
Gear Nut
 

bump
Old 23rd September 2015
  #3
USB is generally fine. Specifically, USB 2.0 is adequate for probably 95% of people who make music on PCs. There is a wide range of performance difference in USB devices, though, and my guess is it's mostly down to driver quality.

The Focusrite Scarletts are at the very bottom end for USB 2 ASIO performance on Windows, while RME is at the very top. (My RME Fireface UFX actually delivers lower latency in USB mode at the same sample rate/buffer size as my MOTU PCIe-424.) Steinberg and Roland are usually right in the middle, performance-wise, and MOTU has better-than-average performance (but not as good as RME).

The main reason to go PCIe (or USB 3, when you can find it) is to support dozens of multiple simultaneous I/O channels. For example, live recordings of concerts or orchestras. I don't even know if anyone is actually producing new PCI-express interfaces anymore? There are several existing devices still on the market, but it seems like the industry is moving away from PCIe and toward Thunderbolt and other technologies for high-track-count devices.
Old 23rd September 2015
  #4
Gear Nut
 

thanks! i wont be doing any recording at all, just in the box production and mixing...So with having heavy projects with loads of vsts...there isnt better cpu performance in pci/pci express over usb? again considering cards with same quality drivers, like an aio over babyface/ufx...


trying to figure if this is the case, and if is than this whole movement towards usb and away from pci/pci express is compromising performance for compatibility...thunderbolt for sure doesn't compromise performance

Last edited by hollo321; 23rd September 2015 at 07:57 PM..
Old 23rd September 2015
  #5
Quote:
Originally Posted by hollo321 View Post
thanks! i wont be doing any recording at all, just in the box production and mixing...So with having heavy projects with loads of vsts...there isnt better cpu performance in pci/pci express over usb? again considering cards with same quality drivers, like an aio over babyface/ufx...
Most of the time, not really. Again it all comes down to how many active I/O channels you are passing through your interface. If you don't have a ton of send/return channels using the interface's I/O or aren't monitoring/recording dozens of external signals at once, there is no practical difference between a reasonably well-performing USB 2 interface or any other type of device.

If all you've got connected to your interface is headphones or L/R outputs to your monitors, the interface is effectively just a 2-channel DAC, and just about any modern audio interface can handle those duties just fine.

As I mentioned before, not all vendors deliver the same quality drivers, so if you have big projects with lots of plugins, latency can be an issue when tracking MIDI (like you might hear a noticeable delay between pressing a key and hearing a plugin instrument play a note), but again, this is a matter of vendor driver quality more than bus type. An RME interface, for example, not only delivers lower latency at the same sample rate/buffer size as competing devices, it will also perform more reliably at very small buffer sizes than most other USB interfaces, meaning you can reach very low latency with it.

When you're working with really huge DAW projects (again, assuming you're not doing a ton of active multi-channel I/O through an interface), the primary strain/bottleneck is on your CPU, not the bus that your interface is sitting on.

Now, it is possible to have a single USB bus that's got a ton of different devices on it contending with each other for bandwidth, but most desktop PCs have multiple USB buses (and you can add your own with add-in cards), and you can remedy contention issues by just putting your audio interface on a quieter bus. PCIe is not exempt from these kinds of problems though, particularly when you have high-end graphics cards in the mix. PCIe slots frequently share resources with other motherboard components, so PCIe alone does not guarantee problem-free top performance.

EDIT: I want to make it clear that I'm talking in terms of actual, practical differences that you can feel when working. On average, PCIe interfaces tend to deliver better low-latency performance than your average USB interface, but most of this has to do with who is making the interface and writing the drivers (RME is top-of-the-heap for PCIe performance just like they are for USB performance, for example). Also the real-world performance difference between a good PCIe interface and a good USB interface is going to come down to low-single-digit milliseconds of round-trip latency most of the time; not a difference that the majority of individuals can feel when recording. There are some people on this forum who claim that they can feel a 2-4ms difference in RTL, but I'm not one of them. I sold my PCIe interface in favor of a FW/USB interface that had more features (and again, my main USB interface slightly outperformed my PCIe interface, anyway, although it wasn't by a margin that I could notice when tracking vocals or instruments).

Last edited by UltimateOutsider; 24th September 2015 at 03:25 PM..
Old 18th February 2016
  #6
Gear Head
 

Quote:
Originally Posted by UltimateOutsider View Post
Most of the time, not really. Again it all comes down to how many active I/O channels you are passing through your interface. If you don't have a ton of send/return channels using the interface's I/O or aren't monitoring/recording dozens of external signals at once, there is no practical difference between a reasonably well-performing USB 2 interface or any other type of device.

If all you've got connected to your interface is headphones or L/R outputs to your monitors, the interface is effectively just a 2-channel DAC, and just about any modern audio interface can handle those duties just fine.

As I mentioned before, not all vendors deliver the same quality drivers, so if you have big projects with lots of plugins, latency can be an issue when tracking MIDI (like you might hear a noticeable delay between pressing a key and hearing a plugin instrument play a note), but again, this is a matter of vendor driver quality more than bus type. An RME interface, for example, not only delivers lower latency at the same sample rate/buffer size as competing devices, it will also perform more reliably at very small buffer sizes than most other USB interfaces, meaning you can reach very low latency with it.

When you're working with really huge DAW projects (again, assuming you're not doing a ton of active multi-channel I/O through an interface), the primary strain/bottleneck is on your CPU, not the bus that your interface is sitting on.

Now, it is possible to have a single USB bus that's got a ton of different devices on it contending with each other for bandwidth, but most desktop PCs have multiple USB buses (and you can add your own with add-in cards), and you can remedy contention issues by just putting your audio interface on a quieter bus. PCIe is not exempt from these kinds of problems though, particularly when you have high-end graphics cards in the mix. PCIe slots frequently share resources with other motherboard components, so PCIe alone does not guarantee problem-free top performance.

EDIT: I want to make it clear that I'm talking in terms of actual, practical differences that you can feel when working. On average, PCIe interfaces tend to deliver better low-latency performance than your average USB interface, but most of this has to do with who is making the interface and writing the drivers (RME is top-of-the-heap for PCIe performance just like they are for USB performance, for example). Also the real-world performance difference between a good PCIe interface and a good USB interface is going to come down to low-single-digit milliseconds of round-trip latency most of the time; not a difference that the majority of individuals can feel when recording. There are some people on this forum who claim that they can feel a 2-4ms difference in RTL, but I'm not one of them. I sold my PCIe interface in favor of a FW/USB interface that had more features (and again, my main USB interface slightly outperformed my PCIe interface, anyway, although it wasn't by a margin that I could notice when tracking vocals or instruments).
Thanks for the super informative post. I'm a noob here. Should I try to get a USB 3.0 audio interface over that of a 2.0? I'm recording max three inputs at once (guitar, mic, and MIDI keyboard). Assume I'm working with an i7 of at least 3.4ghz (possibly 4.0ghz) here.

I'm paranoid about latency.
Old 18th February 2016
  #7
Not much experience with USB interfaces myself, but last I tried with one, the big issue was just connecting it recognized! This was an old Aardvark USB 3 interface, no specific drivers used with this, just generic USB drivers.

For me, this seems to be the biggest issue with anything USB...even my YouRock midi guitar controller with it's USB rareky could get it recognized by my DAW, I gave up & have been using it's standard midi without fail!

With all the above, I can say I'm reluctant to use a USB interface, but no harm in trying it I guess...it'll either work out or not.

I currently use older Aardvark Q10's & Aark 24 cards via PCI, but I don't think there are many new cards using PCI/PCIe these days?

I'm about to try Firewire interfacing for the very 1st time, with my older Tascam 1082 interface/controller. I'll see how that go's!
Old 2 weeks ago
  #8
Here for the gear
 

Quote:
Originally Posted by UltimateOutsider View Post
Quote:
Originally Posted by hollo321 View Post
thanks! i wont be doing any recording at all, just in the box production and mixing...So with having heavy projects with loads of vsts...there isnt better cpu performance in pci/pci express over usb? again considering cards with same quality drivers, like an aio over babyface/ufx...
Most of the time, not really. Again it all comes down to how many active I/O channels you are passing through your interface. If you don't have a ton of send/return channels using the interface's I/O or aren't monitoring/recording dozens of external signals at once, there is no practical difference between a reasonably well-performing USB 2 interface or any other type of device.

If all you've got connected to your interface is headphones or L/R outputs to your monitors, the interface is effectively just a 2-channel DAC, and just about any modern audio interface can handle those duties just fine.

As I mentioned before, not all vendors deliver the same quality drivers, so if you have big projects with lots of plugins, latency can be an issue when tracking MIDI (like you might hear a noticeable delay between pressing a key and hearing a plugin instrument play a note), but again, this is a matter of vendor driver quality more than bus type. An RME interface, for example, not only delivers lower latency at the same sample rate/buffer size as competing devices, it will also perform more reliably at very small buffer sizes than most other USB interfaces, meaning you can reach very low latency with it.

When you're working with really huge DAW projects (again, assuming you're not doing a ton of active multi-channel I/O through an interface), the primary strain/bottleneck is on your CPU, not the bus that your interface is sitting on.

Now, it is possible to have a single USB bus that's got a ton of different devices on it contending with each other for bandwidth, but most desktop PCs have multiple USB buses (and you can add your own with add-in cards), and you can remedy contention issues by just putting your audio interface on a quieter bus. PCIe is not exempt from these kinds of problems though, particularly when you have high-end graphics cards in the mix. PCIe slots frequently share resources with other motherboard components, so PCIe alone does not guarantee problem-free top performance.

EDIT: I want to make it clear that I'm talking in terms of actual, practical differences that you can feel when working. On average, PCIe interfaces tend to deliver better low-latency performance than your average USB interface, but most of this has to do with who is making the interface and writing the drivers (RME is top-of-the-heap for PCIe performance just like they are for USB performance, for example). Also the real-world performance difference between a good PCIe interface and a good USB interface is going to come down to low-single-digit milliseconds of round-trip latency most of the time; not a difference that the majority of individuals can feel when recording. There are some people on this forum who claim that they can feel a 2-4ms difference in RTL, but I'm not one of them. I sold my PCIe interface in favor of a FW/USB interface that had more features (and again, my main USB interface slightly outperformed my PCIe interface, anyway, although it wasn't by a margin that I could notice when tracking vocals or instruments).
Most PCs have only 1 USB 1.1/2 bus and 1 USB 3.0 (aka USB 3.1 Gen 1). Some highend motherboards have an extra USB3.1 Gen 2 bus. I am talking about the physical buses here. All those usb ports with the same type are sharing the bus, so calculate the bandwidth before you decide how many devices you want to plug in at the same time. For example, if i plug 3 USB 3.0 to ethernet gigabit adapters into a single USB 3.0 it's almost going to eat up all bandwidth a usb 3.0 bus can provide (practical: 3.2Gbps) and the rest of devices won't have full bandwidth to run.

For PCIe, they don't share bus, each lane has its own wire to the processor, so you get the full bandwidth. So performance wise you should always use PCIe slots over USB ports.
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