Therefore, in a digital loopback test a negative offset of about 3 ms occurs. This is no real problem, because this way of working is more than seldom, and usually the offset can be com- pensated manually within the application. Additionally, keep in mind that even when using the digital I/Os usually at some place an AD- and DA-conversion is involved (no sound without...).

Note: Cubase and Nuendo display the latency values signalled from the driver separately for record and playback. While with our former cards these values equalled exactly the buffer size (for example 3 ms at 128 samples), the Fireface displays an additional millisecond – the time needed for the AD/DA-conversion. Playback even shows another millisecond added – see Safety Buffer.

Safety Buffer

FireWire audio differs significantly from RME's previous DMA technology. DMA access is not possible here. To be able to transmit audio reliably at lower latencies, FireWire requires a new concept – the Safety Buffer. The Fireface 800 uses a fixed additional buffer of 64 samples on the playback side only, which is added to the current buffer size. The main advantage is the ability to use lowest latency at highest CPU loads. Furthermore, the fixed buffer does not add to the latency jitter (see Tech Info), the subjective timing is extraordinary.

Core Audio's Safety Offset

Under OS X, every audio interface has to use a so called satety offset, otherwise Core Audio won't operate click-free. The Fireface uses a safety offset of 64 samples. This offset is signalled to the system, and the software can calculate and display the total latency of buffer size plus AD/DA offset plus safety offset for the current sample rate.

37.3 FireWire Audio

FireWire audio is in several ways different from RME's earlier PCI audio interfaces. First of all, our cards have a PCI interface which has been developed by RME and optimized for audio. FireWire on the other hand, uses OHCI-compatible controllers that have not been optimized for audio, no matter from which manufacturer they are. Our PCI data transmission is per channel, while FireWire is working interleaved, i.e. it transmits all channels simultaneously. With the Hammerfall, drop-outs thus occur only on the last channels, which is not always noticeable, while a drop-out with FireWire always concerns all channels and is thus perceived much clearer. Apart from this, RME's PCI audio cards establish a direct connection with the applica- tion under ASIO (Zero CPU load), which is principally not possible with FireWire, because communication has to be established by the operating system's FireWire driver. Compared to our PCI cards, the FireWire subsystem creates an additional CPU load at lower latencies.

One FireFace 800 can achieve a performance similar to a PCI card with an optimal PC. An 'optimal' PC has an undisturbed PCI bus. Intel's motherboard D875PBZ e.g., has network, PATA and SATA connected directly to the chipset. No matter what you do with the computer, FireWire audio is not being disturbed. The same holds true for the ASUS P4C800, as long as you leave the additional SATA controller (PCI) unused.

Due to insufficient buffering within FireWire controllers, single peak loads on the PCI bus can already cause loss of one or more data packets. This is independent of the manufacturer and no RME problem. The FireFace 800 features a unique data checking, de- tecting errors during transmission via PCI/FireWire and displaying them in the Settings dialog. Additionally the Fireface provides a special mechanism which allows to continue record and playback in spite of drop-outs, and to correct the sample position in real-time.

Detailed information on this topic can be found in the Tech Info

FireWire Audio by RME – Technical Background on our website:

http://www.rme-audio.com/english/techinfo/fwaudio_rme.htm

User's Guide Fireface 800 © RME

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Intel Fireface 800 manual FireWire Audio, Safety Buffer, Core Audios Safety Offset
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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.
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