Velocity Reviews > XP with USB2.0 PCI card

# XP with USB2.0 PCI card

x1134x
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Posts: n/a

 05-21-2006

Michael wrote:
> Sorry, did you mention the PCI bus speed?
>
> Eg., my HP has 100 mhz FSB, so even with my USB2.0 PCI card I cannot
> approach the USB2 max rates. I need the USB2 protocols to connect devices
> that are not supported by USB1.1 -- but I won't get USB2.0 speeds until I
> upgrade to a computer that supports it.
>
> Hopefully, you have a newer 433 mhz bus -- in which case my comments would
> be irrelevent.
>
> Good Luck
>

Mike, get a computer basics book and study it. If you go start, run,
and type in calc, you have a calculator already on your pc. Use them
both to understand how a pc works.

First of all the PCI bus speed is not the FSB speed they are two
different busses. The fastest the PCI bus speed could possibly be is
133MHz on a very new pc, but most PCI cards won't support that, nor
would they support a 66Mhz bus. The PCI specification for the bus is
33MHz. That being said even a 33Mhz bus will not bottleneck serial
communications. Lets do math! (Its fun!)

First since we know how computers work, we know that the bus is NOT
serial communication it is parrallel. Both the PCI bus and the FSB
(the bus that feeds data into the CPU from all other busses) operate at
32 bits. That means it can handle 32/8 or 4 bytes per clock cycle. Hz
meant Hertz, which is a unit for cycles per second. Mhz is 1 million
cycles per second or 1000000Hertz. Total bit handling capacity then
for 33Mhz is 32*(33*1000000) or 33000000*32 or 1056000000 bits/second.

remember the speeds for USB?

Theoretical max: 503316480 bits/s
Estimated max: 335544320 bits/s
USB 1.1: 12582912 bits/s

Bus speed @ 33Mhz: 1056000000 bits/second. That's exactly twice as
fast as the theoretical max of USB 2.0 which we know cannot be
acheived. Therefore, any bus within the computer operates fast enough
to handle the serial communication of USB.

x1134x