Re: TI-H: special component
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Re: TI-H: special component
On Thu, 18 Jun 1998, Jon Olson wrote:
> Seeing as the PIC only operates at 10 Mhz and the network operates at 100
Just a minor technicality, but I think the high-end PICs max at 20MHz..
They take 4 clock cycles to make an instruction cycle, so it's getting 5
MIPS. A 10 Mb/s (megabit) network (in theory) pushes 1.25 MB/s (megabyte)
of data. So if you had some sort of a shift register taking the data from
the network line and presenting it a byte at a time, then I think a 20
MHz PIC would be able to switch 10 Mb/s network traffic. (Did I calculate
all that correctly?) A 100 Mb/s network (also in theory) moves 12.5 MB/s
down the line. Since a PIC can read its I/O ports in a single instruction
cycle, it can take in 5 MB/s at 5 MIPS. So it has enough room left over to
push 10 Mb/s traffic back out another port, but it doesn't have enough
power to even read in a 100 Mb/s source without losing frames.
So anyway, like Jon said, 100 Mb/s traffic is definitely out. But I think
10 Mb/s might be possible... unless I don't have a clue what I'm doing,
and that is also possible.
--
Greg Hill
greg-hill@bigfoot.com
www.comports.com/link
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