Firewire communication 103 155 another difference is

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FireWire Communication 1:03-1:55 Another difference is the way that FireWire transmits data. FireWire uses a technique called direct memory access or DMA, to reduce amount of load placed on the CPU when transferring data. With DMA, the FireWire bus creates a direct path to system memory, allowing the CPU to be accessed only twice. Once at the beginning of the transfer and once after the transfer is completed. By using DMA, FireWire is able to use isochronous data transmissions. This means the data's transmitted at regular intervals. Without DMA, FireWire would have to wait for the CPU for data to transmit, resulting in asynchronous transmissions. Isochronous communication allows for a constant, uninterrupted bandwidth. In contrast, USB relies on CPU support, which results in inconsistent and interrupted bandwidth. FireWire commits 80% of the bandwidth to isochronous communication. The remaining 20% uses asynchronous transmissions. FireWire Topology 1:56-2:43 FireWire also uses a different typology. Instead of the tiered star typology, FireWire creates a sort of peer-to-peer network with devices by daisy- chaining them together. Up to 63 devices can be connected together this way. One cool thing about FireWire is that this daisy-chain typology actually allows devices to transfer datadirectly between each other without having to go through the computer. For example, a digital video camera could transfer data directly to an external hard drive. The one drawback to this type of typology is device cost. With USB, a lot of the functionality is locatedon the root bus, allowing devices to have less hardware and therefore cost less. With FireWire, most of the functionality is on the device itself. In fact, any device can act as the root bus. This results in higher device costs. FireWire Versions 2:44-3:46 The transfer speed of FireWire depends on which version is being used. There are two main versions of FireWire you should know about. The first is FireWire 400. FireWire 400 or IEEE 1394 was released in 1995 and supports transfer speeds of 100, 200 and 400 megabits per second. In addition, FireWire 400 only supports a cable length of 4.5 meters. FireWire 400 was later improved upon with the release of IEEE 1394A. This released clarified the standard and offered several enhancements, including a power-saving suspend mode for devices. The second version you should know about is FireWire 800 or IEEE 1394B. FireWire 800 was released in 2002. It supports transfer speeds of 800, 1600 and 3200 megabits per second. This version has a maximum cable length of 100 meters. And shortly after the release of FireWire 800, support for peer-to-peer transfer was released with the IEEE 1394.3 standard. FireWire Features 3:47-4:06 FireWire shares a lot of the same features as USB. For one, FireWire devices are hot pluggable,meaning they can be connected to the computer while it is powered on without having to reboot the system. FireWire devices are also self-configuring. This means when you plug in a device, it'll automatically identify itself to the OS and load the appropriate drivers.
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