4. How fast is USB 2.0?
USB 2.0 has a raw data rate at 480Mbps, and it is rated 40 times faster than its predecessor interface, USB 1.1, which tops at 12Mbps. Originally, USB 2.0 was intended to go only as fast as 240Mbps, but in October 1999, USB 2.0 Promoter Group pumped up the speed to 480Mbps.
As far as we know, effective rate reaches at 40MBps or 320Mbps for bulk transfer on a USB 2.0 hard drive with no one else is sharing the bus. Flash Drives seem to be catching up too with the some hitting 30MB/s milestone. For all we know, manufacturers may claim USB interface becoming the performance bottleneck for flash drives as early as 2007.
Additional notes from Alex Esquenet - our engineer friend based in Belgium: "A fast usb host can achieve 40 MBytes/sec. The theorical 60 MB/sec cannot be achieved, because of the margin taken between the sof's (125 us), so if a packet cannot take place before the sof, the packet will be rescheduled after the next sof. On top of that, all the USB transactions are handled by software on the PC. For instance, a USB host on a PCI bus will send or receive the data via the PCI bus; the stack will prepare the next data in memory and receive interrupt from the host."
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BusType: Speed (Mbit/s)
eSATA: 2400
SATA 300: 2400
SATA 150: 1200
PATA 133: 1064
FireWire 800: 786
FireWire 400: 393
USB 2.0: 480 (burst)
Ultra-320 SCSI: 2560
So it has about 1/2 the transfer speed (in burst mode) as an ATA 133 drive (think 250gig 7200RPM IDE drive)... The top quote claims a sustained transfer rate of around 320Mbits, so about 1/3 the data transfer speed...
As for the actual impact on your system... well there are other variables like CPU, RAM, GPU etc...
Makes me feel old when I can remember the ZX81 computer which I think had 16k of memory
And I am fairly sure the ZX81 had 1K of RAM! You had to buy a RAM pack that plugged into the back to give it more...