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KingArthur
Mar 5, 2003, 04:22 PM
Does anyone know the actual specs of Firewire (400) vs USB 1.1? I use an Intel notebook, and I was using a diagnostic program and stumbled across some interesting numbers and wondered if they are correct.

It is telling me that the USB controllers (I have two) are operating at 48Mhz and they have two channels each.
The Firewire/1394 controller (I have one) is operating at 12800Mhz (or 12.8Ghz!) and has 64 channels! I know that there is a major speed difference, but I didn't know that Firewire is that fast! No wonder Apple routes it directly into the system controller! Hell, I have a 1.4Ghz P4. That is about 8 or 9 times faster than my processor!

Just thought it was an interesting figure, and I wanted to see if anyone knows for sure, or if anyone has a diagnostic program that can tell them the speed of their controllers so we can compare.

Computer_Phreak
Mar 5, 2003, 05:02 PM
Originally posted by KingArthur
Does anyone know the actual specs of Firewire (400) vs USB 1.1? I use an Intel notebook, and I was using a diagnostic program and stumbled across some interesting numbers and wondered if they are correct.

It is telling me that the USB controllers (I have two) are operating at 48Mhz and they have two channels each.
The Firewire/1394 controller (I have one) is operating at 12800Mhz (or 12.8Ghz!) and has 64 channels! I know that there is a major speed difference, but I didn't know that Firewire is that fast! No wonder Apple routes it directly into the system controller! Hell, I have a 1.4Ghz P4. That is about 8 or 9 times faster than my processor!

Just thought it was an interesting figure, and I wanted to see if anyone knows for sure, or if anyone has a diagnostic program that can tell them the speed of their controllers so we can compare.


the two mhz values are not the same.

Hz in processors are something like operations per second or something (someone correct me here).

I think the Mhz on the firewire/usb busses are in wavelengths.

TEG
Mar 5, 2003, 05:23 PM
The Hz numbers are equal but are for different purposses. The Proc MHz is the number of times power is cycled per second (aka how many times a second power is turned off to clear the last process. It can then be roughly translated into the number of signals sent through the Proc per second.)(BTW one Set of calculations is done per cycle, the power-off clears that data from the last "gate")

The Hz numbers on FW/USB are relating to how many bursts of signal are sent per second (similar meaning to the Proc Mhz, but linear, not non-linear). So 48 MHz, 48 Million times per second data is sent back and forth to the perifials connected to it.

timbloom
Mar 5, 2003, 05:37 PM
What you would rather compare is the megabits per second, frequency means nothing.. hardly means anything in processors anymore.
USB 1 - 12 Mbps
Firewire 400- 400 Mbps

that should tell you enough right there.

KingArthur
Mar 5, 2003, 11:19 PM
The MB/sec is misleading, too. USB is designed where, you will get 11MB/sec or 480MB/sec for USB2 if you have only one device connected. If you have two devices connected to the USB controller, no matter how much each device uses, it gets half of that so essentially, if you have a mouse and a CD burner both hooked up to a USB 2 controller, and the mouse lets just say uses 1MB/sec (I know that is wrong, but it is just an example) and the CD burner to burn at full speed of say 12x, must maintain 360MB/sec. The CD burner is only given 240MB/sec bandwidth and the mouse is given 240MB/sec bandwidth. Thus, the CD burner can only burn at maybe 8x b/c it is starved for bandwidth and the mouse wastes 239MB/sec of bandwidth. The more devices, connected to the controller, the less bandwidth each device gets, but they all get the same bandwidth. This is the same with both USB 2 and USB 1.1. So if you have a USB 2 CD burner, make sure it gets its own controller to feed off of.

Firewire, on the other hand, divides the the bandwidth into 64 sections, and allocates more sections to a device as needed and then takes them away when the device doesn't need them anymore. If we used the same example as before, the mouse device (or whatever takes up just 1MB/sec) would now have only 6.25MB/sec bandwidth, wasting only 5.25MB/sec. The CD burner would get 362.5 MB/sec of bandwidth it needs so it can burn at 12x (wasting 2.5MB/sec), and 31.25MB/sec of bandwidth would be unused. This is one of the biggest advantages of firewire (other than speed).

Oh, and a side note, guess who developed USB? Can anyone say Intel? lol. No wonder it isn't efficient.

I know I sort of answered my own question, but at the same time, I was more interested to hear if anyone could confirm or deny my system's claim of the speed and number of pathways firewire has. Well, I have confirmed the number of pathways, I just wonder if the speed is accurate, and if so, why is there a speed multiplier of 266 2/3 of firewire over USB, yet only a 36.36 multiplier of throughput. Well, I guess if we have learned nothing else at Apple, it is that Mhz doesn't always tell the whole story.