Why is the FireWire controller chipset important on a PC?
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Q. Why is a dedicated FireWire card with a Texas Instruments (TI) chipset important on a PC?
FireWire was developed by a partnership of Apple, Texas Instruments, and several other companies. FireWire is a great method for transferring streaming data like audio and video, which require a lot of bandwidth and CANNOT have the signal interrupted without serious degradation to the signal. Because this format was developed by Apple, the architecture is optimized for Apple systems. Some PC manufacturers don’t do as well as others integrating this technology.
PC’s base their architecture on a system of interrupts, and typically use synchronous data transfer. FireWire uses asynchronous data transfer, or a specialized version of asynchronous data transfer called isochronous data transfer. Synchronous transfer will guarantee that data packages will be delivered, but will not guarantee that they will be delivered at a certain time. Asynchronous transfer guarantees that packages will be delivered at a certain time, but if there is interference or delay, the packages may be dropped and will not be re-sent. This means that no data will be lost when using synchronous mode, but it could happen that packages are delivered late because they are re-sent if they are lost for some reason. For audio, it's useless if packages arrive late. Late audio is delayed audio and pauses in the audio. The guarantee that audio is delivered on-time is what s important to digital audio; and that's why FireWire audio devices use the asynchronous transfer. Any lost packages will appear as audio drop outs. So, as you can see it is important that FireWire data is not interrupted. However, PC architecture (ACPI) is built on the concept of interrupts. While the interrupts of Windows systems may be problematic, firewire audio can operate efficiently if the data is managed correctly.
This is where the FireWire controller chipset is VERY important. Because timing is so important, there are many controls which manage the FireWire bus to ensure the high transfer rate. The FireWire controller must initialize and release FireWire devices connected to the computer, communicate with all FireWire devices connected to the bus, assist those devices in dedicating a single clock for the timing of the entire FireWire bus, manage the electrical power distributed to the devices, construct a hierarchy of device priority in the system, and manage the data being transferred. There are several FireWire chipset developers that build chips that are significantly cheaper than Texas Instruments, and for this reason, PC manufacturers are starting to use these less expensive chipsets. Unfortunately, many of these other chipsets are not as reliable as those manufactured by Texas Instruments. M-Audio cannot simply say only use Texas Instruments chipsets, because some of these other controllers actually work very well, and M-Audio does not want to endorse any particular manufacturer. Some firewire chipset manufacturers are improving the quality of their controllers, but when problems are encountered, the chipset is the first place to look. When a chipset is in question, M-Audio does recommend using the controller chipsets which have a history of being the most reliable.
Even if your motherboard has an on-board FireWire controller with a Texas Instruments chipset, you may encounter problems because all onboard devices, including the FireWire controller, are run through the Southbridge of the processor. This means that there is a lot of traffic that the FireWire signal must compete with for access to the processor (all USB, onboard audio, onboard video, serial ports, network controllers, etc...). Data coming from all of these devices creates a bottleneck and greatly increases the chance of the FireWire signal being interrupted. The interrupted data is dropped to maintain the delivery time of the rest of the data. When too much data is dropped, the audio signal may be appear as distorted, completely dropped, or the computer may even drop the connection with the FireWire audio device. To avoid this on a PC, we always advise installing a dedicated FireWire card. This is because the PCI bus runs to the Northbridge of the processor. The Northbridge provides more reliable access to the processor because it only manages the data from the PCI, AGP, and memory.