> -----Original Message-----
> From: PCBUILD - Personal Computer Hardware discussion List
> [mailto:[log in to unmask]]On Behalf Of jonathan
>
>
> And Earl says:
> >This sounds quite slow.  A typical "average" transfer rate is about
> >one-tenth of the modem's rating.
>
>
> "about one-tenth of the modem's rating" is true; but, correct me if
> I'm
> wrong, exactly one-eighth. A bit is a 'bi(nary  digi)t.' A binary
> digit is simply
> a 1 or a 0 (in electrical terms an OFF or an ON, though more
> frequently
> a HIGH or a LOW voltage). Eight of these together are called a 'byte.'
> A byte=8 bits. (Incidentally, 4 bits=1/2 byte=a 'nibble'. No kidding.)
> Everything in computer-land is measured in bits and bytes.(The big B
> stands for bytes, the little b stands for bits.)


This is a very simplistic view, which gets many people in trouble when they
start talking about serial communications through a modem.

A modem transmits information one bit at a time.  Since this information is
flowing one bit at a time, there would be no way of telling where one byte
ends and the next byte begins.  Your modem adds extra bits to the data
stream to deal with this.  The extra bits are called start bit and stop bit.
There is also a bit called the parity bit which is used for error checking.
All of these extra bits (if used) must also be sent out through the modem,
so the EFFECTIVE transmission speed is APPROXIMATELY one tenth --- just as
Earl said.


>  When I connect at
> 3.52KB per second (the best I do), this equals 3.52 X 1000 bytes per
> second (3520 bytes) and THAT = 3520 X 8 (=28,160) bits per second. So

Your math is WAY off.  1K is 1,024 bytes not simply 1,000.
It should be:
3.52 X 1024 = 3,604.48 3604.48 X 10 = 36,0448 bits per second.

This same conversation pops up several times a year and seems to always
create a flurry of people posting how fast their modem is.  But there is no
way to compare one modem to another unless they are both in the same
location, using the same phone line, to connect to the same ISP, and using
the EXACT SAME ROUTE across the internet to connect to the same web site.

All of the calculations we just talked about are for the transmission speed
from your modem to you ISP's modem -- ONLY.  Once you start talking about
the internet, then many other factors come into play, most notably
BANDWIDTH.

It's just like driving your car.  Your car may be capable of doing 90-120
Mile Per Hour, but most roads restrict your speed to 55 or 60.  And when you
hit a heavily congested section of the highway, your speed may drop as low
as 30 or even stop completely for a short period of time.  The internet is
just like that; there are many "traffic jams" and bottlenecks.

Add to that the fact that the internet, has it's own version of a "traffic
cop" (officially called a router) that can redirect your "car" to a
different route; and that route can be significantly different even when
reconnecting to the same site again.

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