Hardware Autopsy
at each node in order to prevent the signal from
being intercepted midstream (to prevent anyone
from tapping into and recording the digital bit
stream). If the handshake fails at any point along
the way, that authentication failure is reported to
the playback software.
Furthermore, the audio-video stream is re-
encrypted before it enters the HDCP pipeline,
and it’s decrypted when it arrives at the fi nal
playback device.
DON’T HATE THE PLAYER
Representatives from the companies responsible
for creating these technologies are quick to point
out that they’ve developed “content protection,”
not “copy protection,” systems. The technologies
are inert, they say; it’s up to the movie studios
to deploy them as copy-protection schemes.
HDCP, for instance, simply notifi es the player if
there’s a non-HDCP device in the playback chain.
Software in the player then executes the rules,
(established by the media owner) that are encod-
ed within the content.
One of those rules is known as managed
copy, which allows the consumer to make a limit-
ed number of legal backup copies of an HD DVD
or Blu-ray disc or transfer the copy-protected
content to another device, such as a media serv-
er. Theoretically, this backup copy would be sub-
ject to verifi cation through an online verifi cation
system, which would require the playback device
to be connected to the Internet. Unfortunately,
managed copy still hasn’t been implemented in
the real world.
The Image Constraint Token is a more onerous
rule that gives content owners the power to make
the software stop playing content or downsample
video to 960x540 resolution—a fraction of the
image quality you thought you were buying—if
HDCP is missing at any stage in the playback
chain. This can occur when the video is played
through an analog component connection, but
there are also many early HDTVs, videocards, and
computer monitors in people’s homes that were
manufactured prior to the development of AACS
and HDCP. Owners of Microsoft’s Xbox 360 HD
DVD drive should be aware that since that device
uses a USB connection—considered to be an
unsecure display path—it is also susceptible to
the Image Constraint Token. Sony’s PlayStation
3, on the other hand, is fully HDCP and AACS
compliant (unless you’re using one of its analog
display connections).
The Image Constraint Token is invoked on
a per-disc basis, and as far as we know, no
studio has activated the technology in their cur-
rent releases. In fact, rumor has it that they’ve
informally agreed not to implement it until at least
2012; but that is of little consolation to anyone
who’s still using non-HDCP gear.
Any requests? What hardware—new or old—would you like to see go under
Maximum PC’s autopsy knife? Email your suggestions to [email protected].http://www.maximumpc.com | APR 08 | MAXIMUMPC 69
A PC Fan
Without fans, our computers would be toasty inside. But how does this simplest
of cooling devices actually work, and what’s the difference between a noisy fan
and a quiet one? We delve into the inner workings of this miraculous device to
unravel these mysteries.FAN BLADES When fan blades spin,
they move air. However, everything
from the number and size of blades on
the fan to their pitch to the shape of
the fins impacts both the fan’s
airflow and its noise profile.
POWER CONNECTOR
The common case fan
uses either a four-pin
Molex connector or a
smaller three-pin mother-
board header connector.
Both provide a ration of
DC power; the only differ-
ence is that the three-pin
header also provides
information regarding fan
speed back to the mobo.ELECTROMAGNETS
Most computer fans include a brushless DC
motor that uses four electromagnets to push and
pull magnets attached to the hub of the spinning
portion of the fan. Alternating the polarity on the
electromagnets causes the fan to spin at different
speeds. By winding the motors differently—
connecting the wires on the electromagnets in a
different order—you can adjust the torque and
maximum speed of the motor.