"Bill Kearney" <(E-Mail Removed)> hath wroth:
>Hmmm, so are there any seriously negative issues with the drivers for the
>Senao and Ubiquiti cards?
Sorry, no personal experience.
>I looked at those for their power capabilities.
I'm always amazed at their power output. MMIC power amp efficiency at
2.4Ghz is about 10%. So, to get 400mw of output, the card requires
4000mw of power. Where does the other 3.6 watts go? In heat, or
course. Fortunately, it's only in transmit so the card won't overheat
or melt.
|
http://www.ubnt.com/super_range.php4
Yep, 1.3A at 3.3V in xmit.
>I've never been particularly thrilled with how the inboard antennae on the
>laptop have worked. Getting a card with the possibility of more power holds
>some appeal.
The antenna problem is usually the type and location of the laptop
antennas. Some are no better than a joke. For example, the antennas
on the Compaq 2120US are under the display hinges, a truly hideous
location:
|
http://802.11junk.com/jeffl/antennas...aq-2120us.html
That's a 1/4 wave meandering monopole, on high loss G10 circuit board.
If you look closely, the black coax was seriously crunched by the
hinge, which is what inspired the dissection and repair job.
Hopefully, the Toshiba antennas are somewhat better.
>I find it somewhat odd that the miniPCI cards would be described similarly
>to a winmodem. Given it's a PCI bus you'd think the cards would be as
>capable as a regular PCI card, certainly more than a PCMCIA slot device.
The comparison with a Winmodem is mine and of course, since it's mine,
must obviously be correct. Prior to Winmodem type technology, almost
all of the data extraction and encoding for modems was done in
hardware. The card presented itself to the ISA or PCI bus as a UART,
with parallel ASCII data ready for consumption by the processor. The
problem was that every time a character arrived, the UART would toggle
a hardware IRQ line, the interrupt would cause the CPU to flush
everything into the stack, and execute the serial interrupt routine.
That was fine for 1200 baud modems, but as the data started coming
faster and faster, the constant CPU interruptions for every character
became a big load on the system.
So, the solution was to move much of the processing into the CPU.
Since the data was already in the CPU, it didn't need to cross back
over the ISA or PCI bus. There was no need to execute CPU cycle
gobbling IRQ's. As an added bonus, it saved a bunch on hardware
costs. At first, the 286 vintage processors had a difficult time
doing the character decoding and processing. It was a gutless
processor and couldn't keep up. This gave the Winmodems an
undeservedly bad reputation.
However, as processors and memory started to improve, less and less of
the processors daily life was spend dealing with serial data in and
out of the modem. I think it was the 486DX25 vintage where the CPU
load from a UART type modem, was equal to the CPU load presented by a
Winmodem. As CPU's became even faster, the percentage CPU load for
the Winmodem was drastically reduced to almost negligible.
Eventually, the same problem appeared with wireless devices. Why ship
expensive hardware when there's a handy CPU that can do the same work
for free? While the original wireless PCMCIA cards had chips that did
most of the MAC layer crunching, the later and cheaper cards, along
with MiniPCI and USB wireless just had the CPU do the MAC layer stuff
(retrans, error control, PAD, power management, ad nausium). Most
wireless routers contain a dedicated MAC chip to do this job, but the
smaller MiniPCI and USB devices do it in the driver.
Does the monstrous 80Mbyte (compressed) Intel Proset download give you
a clue as to where the real work is done?
>Or, much like modems, does it vary from card to card?
In the PCMCIA and PC Card area, it does vary. Some have MAC chips,
some do it in the driver. However, in the USB and MiniPCI area, all
of them do the MAC layer stuff in software/drivers. Of course,
routers and access points do it in a dedicated MAC chip
>-Bill Kearney
--
Jeff Liebermann
(E-Mail Removed)
150 Felker St #D
http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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