chessrock said:
Due to the architecture of the firewire platform, it's possible to utilize several firewire devices, simultaneously, within the same application ... and to have that application control the various devices without fear of drift, phase shift, and other clocking-related artifacts.
The same can be said of USB, at least to a degree:
As to the first part, anybody who has printed or faxed documents from a USB drive (optical or magnetic) to a USB fax/printer while using their USB mouse to navigate their windows has used three simultaneous USB devices from the same driver.
As to the second part, I make no claim as to remembering all the intrinsics of sync and handshaking contrasting the FW and the USB protocols; there may very well be tech issues such as jitter and the like that are easier to overcome in FW than in USB, I'm honestly not sure (Not that FW hasn't hae it's own jitter problems in implementation over the years; it famously has.)
However, I will say that there seems to be no issue in running two audio streams over USB1.1 with no synchronization problems. And this is with other USB devices also running simultanously. Even if we were to assume that two audio streams (at ~2.3Mbit/sec total) were the most that 1.1 could handle because the rest of the bandwidh (other than for other devices) was needed for checksumming, synchronization, etc. that would mean that about 20% of USBs capacity was "useable" for such an application or calculation. Now frankly, this is ridiculous; there is no way that USB is *that* inefficient. But for the sake of worst-case-scenario discussion, let's say that 80% inefficiency were true. Extrapolated to USB2.0, this would mean that about 96Mbits/sec were available for stable streaming. This would mean a *worst-case-scenario* of the equivalent of over 80 simultaneous channels of audio at 48k/24 on USB2.0.
chessrock said:
Firewire was originally designed and intended specifically for audio and video, and with the needs of audio and video in mind ... while USB was originally intended for mouses and keyboards, etc., I believe, but don't quote me on that.
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Oops, I am quoting you, chess. But don't worry, I am agreeing with your quote
. Here's the full story as I understand it. It may not be 100% accurate, but it's a LOT closer to the truth than the Myth of USB.
USB (Universal Serial Bus) was originally designed and marketed to replace the old-fashioned and extremely slow serial and parallel ports while at the same time jumping over SCSI in data bus performace attributes,and was an initiative that (I think) was either started by or largely led by Intel to help keep the Wintel PC platform up-to-date in competition with Apple. Firewire was, OTOH, earlier developed by Intel's then-nemesis, Apple. Apple later brought the spec to the IEEE who approved it for the most part as cross-platform standard IEEE-1394.
Not long after FW came to be championed in the Apple community, the video market elected it for video stream transfer. Sony started it out, I think, and before you know it, everybody else followed suit. This was all more-or-less while Intel was still hashing out USB as a seriel/parallel/SCSI replacement.
So the table was pretty much already set; between Apple's hometown support of their own FW standard, their domination in the A/V/G workstation platform market, the video industry's adaptation of FW, and the perception that USB was/is meant mostly for peripherial device connection than it is for data streaming, FW has pretty much become the de facto standard for media streaming and high-speed data transfer.
Because it takes way too long to explain all that
, it became much easier to make up the shared myth among sales and marketing types that USB simply wasn't fast enough; this myth had the advantage of implying that the (at the time) faster FW was "better" and therefore was worth paying premium markup for. Otherwise it would be hard (for a sales guy and his custy who both want easy preset explanations, at least) to justify why most Wintel platforms at the time came with USB ports (because that was Intel's baby) but a seperate FW I/F card had to be bought.
Nowdays, PCs with both USB and FW built-in are common place, but the myth of USB being insufficient for most high-speed needs still persists.
G.
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