PCI vs. Firewire

[ddclark777]

I currently am using a MOTU 2408mkII with a PCI-324 card on a dual G4 800. The idea of using the PCI card when USB 2.0 and Firewire are so readily available seems a waste but the fact that MOTU came out with the 2408mkIII which still uses a PCI card made me wonder if my feelings were legitimate. I've been reading up on the MOTU 828mkII which seems to be a good alternative, but it only has 1 ADAT optical connection equal to 8 channels of lightpipe whereas my 2408 has 3 for 24 channels of digital audio. Do I really need 24 channels of digital audio?

 

Thanks!

[b_3guy]

I have the original Motu 828 & I'm quite happy with it. Three other friends of mine use a PCI hookup to 2408's & a 1224. They don't seem to have any need to move on to a Firewire interface. I think if you were going to buy a new interface I would go Firewire, just because it's simpler. One of the friends had to buy a new PCI card because he updated to a G-5. I could have made do with a 2in/out interface but I thought if I ever wanted to record a drummer, I would like 8 ins/outs. So I got my 828. After having a couple of drummers in here & getting poor performances out of them, I've moved on to using Drums on Demand acoustic drum loops.

[ksoper]

It was my understanding (although admittedly rudimentary)that a PCI connection on a PC went "straight to the board," in other words, was the most direct connection to the computer. On an Apple product, though, you have the benefit of native firewire. Without reviewing benchmarks, I don't know if firewire on an Apple is as fast or faster than PCI on a PC or Apple. On a PC, firewire, to my understanding, goes through a translation of sorts--a bottleneck. I use external firewire drives for audio and streaming samples. Works fine.

 

I had so much legacy software that I've chosen to stay with a PC-based system and a PCI interface. With your G4, a firewire interface may be just fine. And then it comes down to your needs. I only need eight inputs and in actuality, I mostly only use two at a time.

 

Does any of that help?

 

k.

[Dan Phillips]

Firewire is significantly slower than PCI.

The idea that firewire is "native" on one platform and not on another is a misnomer. Implementations may vary, but it is a bus, and as such will always present a bottleneck - just like PCI. The question is merely whether or not your data stream will fit through the bottleneck.

 

Personally, I would not look at the issue in these terms at all.

Rather, I would look at the actual implementations of the audio devices.

 

In the case of MOTU, the firewire devices are undoubtedly cool. If you want to move them around, or connect to a laptop, they are the obvious solution.

 

On the other hand, MOTU's PCI devices offer better integration for large multiple-interface setups, allowing low-latency hardware monitoring between devices. That's a critical app for me, personally, since I use my MOTU setup as my mixer and monitoring environment, as well as my audio interfaces.

 

- Dan

[ddclark777]

Thanks to all of you who have taken the time to reply. I guess it's one of those "if it ain't broke... yada, yada, yada..." situations. Hearing that FW is actually slower than PCI is surprising not from any prior knowledge, just the fact that FW is a newer technology, therefore I assumed it faster. So, it sounds like there is no real reason to change at this point?

[Loufrance]

Originally posted by Dan Phillips:

Firewire is significantly slower than PCI.

The idea that firewire is "native" on one platform and not on another is a misnomer. Implementations may vary, but it is a bus, and as such will always present a bottleneck - just like PCI. The question is merely whether or not your data stream will fit through the bottleneck.

 

Personally, I would not look at the issue in these terms at all.

Rather, I would look at the actual implementations of the audio devices.

 

In the case of MOTU, the firewire devices are undoubtedly cool. If you want to move them around, or connect to a laptop, they are the obvious solution.

 

On the other hand, MOTU's PCI devices offer better integration for large multiple-interface setups, allowing low-latency hardware monitoring between devices. That's a critical app for me, personally, since I use my MOTU setup as my mixer and monitoring environment, as well as my audio interfaces.

 

- Dan

I agree, I'm a PC user so I don't know mac's to well. Sounds to me like firewire would be ok, Pci is a direct connection to the board but the whole system has to be kept in mind (meaning is the PCI bus overloaded already? I doubt) Firewire and Usb 2.0 would only be a problem if you had a bunch of firewire or usb stuff hooked up and they were fighting for bandwith. But like I said this is from a PC perspective. Personally I'd take the Firewire but thats only because It's a convience, I don't mind cracking open a case and putting in a PCI card but I like the idea of being able to move and connect a device to diffrent systems.

[ksoper]

Originally posted by Dan Phillips:

Firewire is significantly slower than PCI.

The idea that firewire is "native" on one platform and not on another is a misnomer.

Thanks for the clarification. Too many damn holes in my education.

 

k.

[Byrdman]

Originally posted by ksoper:

Originally posted by Dan Phillips:

Firewire is significantly slower than PCI.

The idea that firewire is "native" on one platform and not on another is a misnomer.

Thanks for the clarification. Too many damn holes in my education.

 

k.

There are two issues - no - three issues!

 

1/ Transfer speed.

 

The slowest Firewire is 40Mb/sec so that's fast enough for a lot of tracks.

 

2/ Latency. How long after a sample is available does it take to get it to the DAC (or from the ADC). Part of this is buffering. When you use an interface like Firewire with a protocol it has to do buffering. That imposes a delay of some number of cycles.

 

3/ CPU overhead. OK, so no buffering is the fastest possible way of moving data, and PCI can do this, but PCI is slow compared to CPU speeds and if the cpu had to go get (or put) each sample one at a time it would slow to a crawl. So actually you still need buffering (and data is in fact transfered by DMA)

 

End result is it doesn't make significant difference which way to go - any advantages in the hardware (of PCI) can be more than lost in the quality of the software. I am not saying the PCI software you have is bad but that if it were bad, it would have a bigger influence on performance than the use of a different buss.

[Dan Phillips]

Originally posted by Byrdman:

There are two issues - no - three issues!

Transfer speed, bandwidth, and a fanatical devotion to the Pope.

(apologies to Monty Python.)

:-)

 

Originally posted by Byrdman:

The slowest Firewire is 40Mb/sec so that's fast enough for a lot of tracks.

Absolutely - as long as there's nothing else on the bus. What I was trying to say above, however, is that the bus itself is not the issue (at least with regards to MOTU hardware, which seemed to be the initial focus).

 

The important part for me is the scalability of the zero-latency CueMix console. With the PCI interfaces, this comes for free; all connected interfaces (up to 4 with the PCI-424 card) are part of the same monitor mixer. I currently have three interfaces, with a fourth coming in a few days, so this is important to me.

 

To get similar functionality with the firewire interfaces, you have to use additional channels of physical I/O, as described here:

 

http://www.motu.com/techsupport/technotes/document.2004-06-25.8708037598

 

Best regards,

 

Dan

[JeffLearman]

The Firewire versions have zero-latency monitoring as well, because that all happens directly inside the unit without going through your computer.

 

Furthermore, latency is an overall system issue. You can get very low latency over firewire. You can get even lower latency over PCI, because it is more directly connected to your CPU than firewire in ANY computer built today.

 

However, the difference in latency between the two is probably less than a millisecond or two. Since sound travels at about one foot per millisecond, that's equivalent to the latency of stepping one or two feet further from your monitor speakers. Therefore I doubt it's significant.

 

For 8 tracks in and out at 24-bit/44kHz, Firewire is fine. I haven't done it (since I also have the older 828, which tops out at 48k), but I bet it's fine for 24-bit/88kHz.

 

At 24 channels of 24-bit/192kHz, well ... I'd have to do the math, and then I'd have to try it to see. (Not to mention that I'd need 3 units.)

 

Do you need 24 channels? Only you can answer that. Few home studios do! You can do a great job recording a drum kit with 8 inputs. For live (or "live in the studio") recording, 8 is only enough if you're doing minimal drum miking and with a simple band setup. 16 is plenty for most cases but not for fancy band setups or super-pro-level work.

 

What do you use ADAT for? Note that an ADAT lightpipe is either 8 channels of 16/48k or 4 channels of 24/48k.

 

With an 828 mkII, you actually get 10 analog inputs (funny how often 8 is just not quite enough, when recording a band, but 10 is enough) plus the ADAT lightpipe, so if you have an analog-to-ADAT converter (or even a cheap old "blackface" recorder to use that way) you get a total of 18 channels with the 828mkII.

 

Bottom line: there's nothing wrong with your current unit, so unless there's money burning a hole in your pocket, stick with what you have.

[Bob Rinker]

Originally posted by ddclark777:

Thanks to all of you who have taken the time to reply. I guess it's one of those "if it ain't broke... yada, yada, yada..." situations. Hearing that FW is actually slower than PCI is surprising not from any prior knowledge, just the fact that FW is a newer technology, therefore I assumed it faster. So, it sounds like there is no real reason to change at this point?

One thing not mentioned about speed - PCI is a 32 or 64 bit wide *parallel* bus, whereas Firewire is a four wire (two for send, two for receive) wire *serial bus*. So, in terms of raw speed, the "old" 33MHz bus can transfer 132 megabytes (or 1056 megabits) per second. The 66MHz buses double that, and 64 bits doubles that again. Raw firewire speed is 400 megabits per sec, or about 40 megabytes/sec. In addition, there are separate control lines on PCI, so a bus "transaction" involves twiddling those lines - very fast. Firewire doesn't have separate control lines, so control information must be sent down the same serial wires, thereby reducing the effective data transfer rate. Firewire has separate send/receive lines so can do so simultaneously, whereas a PCI transaction will be a single direction at a time. So the two standards are quite different animals.

 

Having said all that, either is plenty fast for many channels of audio. Any perceived latency in the system will be due to the way the software handles it (ie, buffering, etc.), rather than the speed of the underlying hardware. This is different from MIDI, which is around 31 kilobits (= 0.031 megabits)/second!

 

Hope this helps.

 

- Bob

[Dan Phillips]

Originally posted by learjeff:

The Firewire versions have zero-latency monitoring as well, because that all happens directly inside the unit without going through your computer.

Yes, but it's not as scalable as the PCI systems - see above. Again, this is a comparison of the respective MOTU systems, and not a comment on Firewire vs. PCI in general.

 

Originally posted by learjeff:

Note that an ADAT lightpipe is either 8 channels of 16/48k or 4 channels of 24/48k.

ADAT lightpipe can carry 8 channels of 24bit/48kHz audio.

 

You may be thinking of S/MUX, which is an unofficial standard for carrying 4 channels of 24-bit/96kHz audio over the lightpipe.

 

- Dan