Fireface 800 and External Firewire 800 HD?

[Matthew Murray]

Hi all. I'm using a FF800 as my interface, and I'm going to be running it right to the brim (spdif and 16 channels adat, all happening at once). I'm thinking I should probably connect it via firewire 800, but I've also got a firewire 800 hard drive which I use as my tracking HD.

Question is -- when I'm chaining the two units to my G5's only firewire 800 port, should it be the hard drive first, and then the FF800, or vice versa? Or does it even matter? Buying cables and I want to make sure I get proper lengths and all that.

Thanks :-)

[Schmacko]

I think the FF only works when connected directly to the computer. So, that would mean you'd be connecting the drive to the FF.

Why not just connect your drive to one of your FW400 ports with a 800->400 FW cable?

[Matthew Murray]

I suppose I'd just like to get the most juice out of the hard drive too. But perhaps having it on the 400 bus would make things run smoother anyways.

[DrDeltaM]

Even when using all I/O, there's no need for FW800.

For example, at 48kHz:
48000 x 24 bit = 1 152 000 bits = 144 000 bytes / sec for one input or output

The Fireface has a total of 56 inputs and outputs together, so:

56 x 144 000 bytes/sec = 8 064 000 bytes/sec = 7875kbyte/sec = 7,7 Mb/sec

FW400 is 400 megabits/sec = 50 Mb/sec

Headroom enough ;-)

[Matthew Murray]

Whoa. Is that math right? If so, I'm just going to keep the FF800 on FW400, and put the hard drive on FW800. Are you sure of your numbers, Mr. Delta? You're right then, that's more than enough headroom. :-)

[DrDeltaM]

Originally Posted by Matthew Murray

Whoa. Is that math right? If so, I'm just going to keep the FF800 on FW400, and put the hard drive on FW800. Are you sure of your numbers, Mr. Delta? You're right then, that's more than enough headroom. :-)

Yes, those numbers are correct

[Matthew Murray]

Thanks Doc.

[Branislav]

Originally Posted by Matthew Murray

Question is -- when I'm chaining the two units to my G5's only firewire 800 port, should it be the hard drive first, and then the FF800

If you connect it like this, you can use the drive even when FF800 is switched off, that's about the only advantage.

Branislav

[thomashenry]

Originally Posted by DrDeltaM

Yes, those numbers are correct

I'm not so sure. FW isoc streams also contain a lot of data which is formatting data in addition to audio. It's not nearly as simple as your maths suggest. I'm not sure about the exact configuration of isoc transmitters on the FF, but assuming it is 2 transmitters of 14 channels in each direction, the required bandwidth at 48kHz would be approx:

each packet:
14 channels * 8 samples * 32 bits per sample (even for 24 bit audio) + 64 bits of CRC + 96 bits of header data = 3712 bits per packet

then

size of packet x 4 transmitters x 8000 packets per second

= approx 14.2 meg/second.

[Matthew Murray]

So wait, 14.2 meg/second for how many channels of audio? The full 56?
If so I'd say that still comes in under the 50 megs a second that firewire is...

[DrDeltaM]

Originally Posted by thomashenry

I'm not so sure. FW isoc streams also contain a lot of data which is formatting data in addition to audio. It's not nearly as simple as your maths suggest. I'm not sure about the exact configuration of isoc transmitters on the FF, but assuming it is 2 transmitters of 14 channels in each direction, the required bandwidth at 48kHz would be approx:

each packet:
14 channels * 8 samples * 32 bits per sample (even for 24 bit audio) + 64 bits of CRC + 96 bits of header data = 3712 bits per packet

then

size of packet x 4 transmitters x 8000 packets per second

= approx 14.2 meg/second.

Yes, I didn't take this into consideration, I was purely counting the audio data, not a tech guy to know all those firewire protocol details, my mistake :-) It's probably why some companies like MOTU choose to have their own format running of a firewire-type of connection.

[SONICA]

Hi,

the only time you will need Firewire 800 is when using more than one Fireface 800.
When using one Fireface it will not use more than Firewire 400.

What you have to worry about is using a hard disk and the Fireface 800 on the same Firewire bus.

If possible run the Fireface 800 and the hard disk on two different Firewire controllers.


Best regards,

Guy Cefalu

Sonica Audio Labs

[insomnio]

Originally Posted by SONICA

Hi,

the only time you will need Firewire 800 is when using more than one Fireface 800.
When using one Fireface it will not use more than Firewire 400.

What you have to worry about is using a hard disk and the Fireface 800 on the same Firewire bus.

If possible run the Fireface 800 and the hard disk on two different Firewire controllers.


Best regards,

Guy Cefalu

Sonica Audio Labs

Thanks for putting it so clear.

By the way, I own a Sonica-X...very nice.

________________
Insomnio

[Matthew Murray]

Yes indeed, thanks kindly for that. One fireface on the FW400 bus, and HD on the FW800 bus, is the route i'm going to take i think.

Thanks all for your input!

[ejsongs]

Originally Posted by SONICA

Hi,

the only time you will need Firewire 800 is when using more than one Fireface 800.
When using one Fireface it will not use more than Firewire 400.

What you have to worry about is using a hard disk and the Fireface 800 on the same Firewire bus.

If possible run the Fireface 800 and the hard disk on two different Firewire controllers.


Best regards,

Guy Cefalu

Sonica Audio Labs

not sure if this is true for 2 reasons:

1. on my 2.0 g5 i have 5-7 firewire 400 drives connected at the same time as my fireface 800. the trick to getting it work is that the ff800 has to be turned on first in order to grab the bus first.

2. on g5 (at least the older ones) the 800 and 400 bus are the same.

ej

[ADino]

Hi, Im new here, and I have to say the advice and info on these boards is fantastic..
On this subject, I found the FF to work best when running off its own bus, so Ive installed a LaCie FW 800 PCI, slot 4 on a G5, run my ext HDD's off that, FF running off the internal 400 all by its lonesome, as Im only using 1 FF.

[quincyg]

fyi,
the g5's have had a lot of problems reported when using both the 400 and 800 bus's at the same time. i ran into hard drive corruption doing this and finally after alot of searching found out about this issue. i bought a lacie fw800 card and put my fireface on it and run my sample hard drive from a fw400 port. problem solved. i do all tracking to an internal sata drive which is blazing. i can get 16 channels recording adat with 20-30 tracks playing without and problems.
if its working for you then no problem. if your drives start acting weird then think about my suggestion. my symptoms were external hard drive that would just transfer data slower and slower over the course of days. i would repair drive with disk utility and then it would become corrupt again over the next days again.

[SONICA]

Originally Posted by ejsongs

not sure if this is true for 2 reasons:

1. on my 2.0 g5 i have 5-7 firewire 400 drives connected at the same time as my fireface 800. the trick to getting it work is that the ff800 has to be turned on first in order to grab the bus first.

2. on g5 (at least the older ones) the 800 and 400 bus are the same.

ej

Hi,

not only is true but also a requirement stated in the Fireface 800 users guide.


Best regards,

Guy Cefalu

Sonica Audio Labs