[NTLUG:Discuss] Re: need hardware config recommendations

[Steve Baker]

Robert Pearson wrote:

>>One key thing about PCI-e is the idea that these 'lanes' of serial
>>data are capable of operating over distances of a few feet.  Several
>>companies I've talked to have indicated that they plan to work towards
>>a situation where the PCI-e lanes are brought out of the PC on exernal
>>connectors.
> 
> 
> What about Wireless? Same concept, just no wires. Wireless rates too slow?

Fundamentally, there is a problem with wireless.  It's an omnidirectional
broadcast signal.  That means that everyone and everything within range
is sharing whatever bandwidth there is.

Whilst wires are somewhat inconvenient, they have the advantage that they
take the signal from where it's source to where it's needed.

Furthermore, wireless communications can't just pick any old frequency
they'd like.  There are issues of not interfering with other uses for
radio.  Systems like 802.11 are operating in the 2GHz band.  They are
FUNDAMENTALLY prevented from ever transmitting data at more than 1Gbit/s.

However, picking higher frequencies may have dire consequences for
broadcast range,  or what the signal will penetrate through - or
health risks for end users.  Then there are the regulatory issues.
It's not enough to find a frequency band that's free here in the USA,
if manufacturers are going to use it, just about every developed
country on the planet has to agree to let them broadcast there.

This means that in the very long term, omnidirectional broadcast - for
all of it's convenience factor - isn't the way to go for maximum bandwidth.

But forget the indefinite future - look at the state of the art:

Wireless speeds:  Bluetooth-2 is 3Mbits/s, 802.11g is 54Mbit/s

Cable speeds: PCI-express is 4,000Mbits/s per lane!  With a fairly
'normal' 16 lane interface, you have 64,000Mbits/s!

But it's even worse than that:  Your 802.11g interface will only
deliver 54Mbit/s if you are the only person using it.  If you used
it to connect your hard drives, graphics card and LAN - then you'd
be down to some fraction of that because those three devices would
have to share the bandwidth three ways.

Now put your PC in a office with 50 other people - and your bandwidth
is cut a hundred-fold.  You don't want your hard drive or your
graphics card connected to the CPU using something with the speed
of a 56kbaud modem!

> Look at how many PC peripherals are Wireless now...

Yeah - but they are keyboards (1 byte per second - maybe 10 bytes per
second if you can touch-type!), mice (20 bytes per second),
joysticks (20 bytes per second) Bluetooth headsets (maybe 10kbits/s).

A graphics card (when playing Doom-3 over an AGP bus) needs about
10Gbits/s in it's 'high detail' mode.

That's 200 times faster than the fastest consumer-grade wireless
link you can buy.

A 2x SLI 8-lane nVidia setup chews through 64Gbits/s - which is
over 1000 times faster than a modern wireless link.

> I have been asking the Storage vendors when they were going to
 > deliver Wireless Storage. They all fall down laughing up to now...

Well, yes.  They have a point.

USB hard drives are pretty slow compared to ATA or SCSI drives,
but even a lowly USB-2 port gives you 480Mbits/s - ten times what
802.11g gives you.

It's possible people might come up with wireless hard drives for
the convenience factor - but they'll never be as fast as USB - and
USB is pretty slow compared to a state-of-the-art hard drive interface.

Serial ATA is 1200Mbits/s - more than 20 times the speed of wireless.

---------------------------- Steve Baker -------------------------
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