37.4 Number of Channels and Bus Load

As explained in chapter 37.3, FireWire Audio does not reach the same performance as PCI audio. On a standard computer with modern single PCI bus, about 100 audio channels can be transmitted per direction (record/playback). Exceeding this limit, any system acitivity - even outside the PCI bus - causes drop outs.

Transferring these experiences to FireWire and the Fireface 800 means that besides the num- ber of channels the bus load has to be taken into account too. One channel at 96 kHz causes the same load to the system as two channels at 48 kHz!

To use FireWire as efficiently as possible, the Fireface allows to reduce the number of trans- ferred channels. Limit Bandwidth provides four options, limiting the transmission internally to 28, 20, 12 or 8 channels. This limitation is independent from the sample rate, which is why the op- tion's descriptions are not fully correct at 96 kHz. As can be seen in the following table, in 96 kHz mode there is no difference between the setting All Channels and An.+SPDIF+ADAT1. For a valid reduction of the bus load ADAT must be unselected completely. As the Fireface offers only 12 channels in Quad Speed mode, the options All Channels (28 channels) down to Ana- log+SPDIF (12 channels) perform no change at all. Logically, as ADAT isn't available in this mode anyway.

Limit Bandwidth

48 kHz (28)

96 kHz (20)

192 kHz (12)

FW-Kanäle

All Channels

x

/

/

28

An.+SPDIF+ADAT

x

x

/

20

1

 

 

 

 

Analog+SPDIF

x

x

x

12

Analog 1-8

x

x

x

8

The bus load is doubled at 96 kHz and quadrupled at 192 kHz. Limit Bandwidth sets a constant number of channels, but those channels cause a bigger load in DS and QS mode, because more data have to be transferred. For example the 12 channels at 192 kHz equal a FireWire and PCI bus load of 48 channels at 48 kHz! The following table shows the real bus load in all modes.

Limit Bandwidth

48 kHz (max 28)

DS (max. 20)

QS (max. 12)

All Channels

28

40

48

An.+SPDIF+ADAT

20

40

48

1

 

 

 

Analog+SPDIF

12

24

48

Analog 1-8

8

16

32

The usage of multiple Firefaces in DS and QS operation can be problematic due to the in- creased bus load. Some examples:

2 Firefaces will most likely not run stable at 192 kHz at full track count. 2 x 12 channels 192 kHz equal 2 x 48 channels at 48 kHz = 96 channels per direction.

2 Firefaces at 96 kHz should operate reliable at full channel count. 2 x 20 equals 2 x 40 = 80 channels per direction.

3 Firefaces at 96 kHz can't operate at full channel count (3 x 20 equals 3 x 40 = 120 chan- nels per direction). The Settings dialog will show Errors, audio will sound distorted.

To not exceed a maximum of 80 channels with 3 Firefaces at 96 kHz, a setting like Ana- log+SPDIF is recommended to be used on all Firefaces. This equals 3 x 24 = 72 channels per direction.

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User's Guide Fireface 800 © RME

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Intel Fireface 800 manual Number of Channels and Bus Load, Limit Bandwidth 48 kHz 96 kHz 192 kHz FW-Kanäle

Fireface 800 specifications

The Intel Fireface 800 is a powerful audio interface celebrated for its high-performance capabilities and versatility in both studio and live settings. Designed to cater to the needs of musicians, producers, and sound engineers, it stands out with its rich feature set and reliable technology.

One of the defining features of the Fireface 800 is its support for an impressive 26 input and 28 output channels. This extensive I/O configuration facilitates seamless integration with a wide variety of audio production setups, allowing users to record multiple instruments simultaneously or create complex routing scenarios. The unit also boasts top-notch analog and digital converters, ensuring pristine sound quality with a dynamic range that captures the nuances of any audio source.

In terms of connectivity, the Fireface 800 is equipped with both FireWire and USB ports, making it compatible with a range of computers and devices. The device utilizes the FireWire 800 protocol, which delivers higher data transfer rates compared to its predecessor. This efficient transfer capability is crucial for maintaining audio fidelity and reducing latency, making it an ideal choice for real-time monitoring and recording.

The Fireface 800 also features standalone operation capabilities, functioning independently of a computer when needed. This is particularly useful for live performances, where reliability and reduced setup complexity are essential. Users can easily connect microphones, instruments, and other equipment directly to the Fireface 800, making it a versatile tool for a variety of scenarios.

With its low-latency driver technology, the Fireface 800 ensures smooth performance even when handling demanding audio tasks. Its advanced ADAT and S/PDIF digital inputs and outputs provide further flexibility for connecting other gear, such as additional preamps and effects processors.

Another noteworthy characteristic of the Fireface 800 is its robust build quality. Designed for regular use in professional environments, the unit features a rugged metal chassis that can withstand the rigors of transport and daily use. This ensures longevity and consistent performance for audio professionals who depend on reliable equipment day in and day out.

In summary, the Intel Fireface 800 is a versatile and powerful audio interface that caters to a wide spectrum of audio production needs. With its extensive I/O capabilities, high-quality converters, reliable connectivity options, and robust design, it continues to be a popular choice among audio professionals striving for excellence in their work.