more signifi cant in that they increase the
memory’s overall performance: The new
memory doubled the size of GDDR3’s
prefetch scheme from 4 bits to 8 bits, and its
burst length was locked at 8 bits (GDDR3 sup-
ports either 4- or 8-bit burst lengths). Prefetch
enables the memory chip to anticipate the
need for data and grab it before the GPU asks
for it, reducing the time the processor has to
wait. Burst length defi nes the amount of data
sent in burst mode, a process in which data
is transmitted without waiting for input from
another device, such as the GPU. GDDR4’s
8-bit burst length might be one reason Nvidia
ultimately passed on this type of memory:
Nvidia’s processors support only 4-bit burst
lengths. With ATI (now AMD) being the only
major customer for GDDR4, just two manu-
facturers—Samsung and Hynix—decided to
manufacture it. This circumstance has kept
the price of the memory relatively high.
SUCCESSFUL MUTATION?
GDDR5 is the next major development in
graphics, and as with GDDR4, AMD’s ATI
division has already paired it with its higher-
end GPU: the Radeon HD 4870. Nvidia con-
tinues to hang back, professing satisfaction
with the performance of GDDR3.
GDDR5 requires just 1.5 volts of electri-
cal power, which should make the memory
run cooler—a feature that could aid in over-
clocking, reduce manufacturing costs, and
extend battery life if used in a notebook PC.
The new memory’s prefetch and burst length
remain the same as that of GDDR4: 8 bits on
both counts.
GDDR5 technology supports densities
ranging from 512Mb to 2Gb, so it would
require just four 2Gb modules to create a
1GB frame buff er (here again, however, real-
world parts are currently limited to 512Mb
and 1Gb). Boasting a raw theoretical data
rate ranging from 3.6Gb/s to 6Gb/s (although
we won’t see that upper limit for several
years), GDDR5 promises to deliver twice the
memory bandwidth of GDDR3 running at the
same clock frequency.
More practically, that high data rate also
enables a GPU manufacturer to achieve
nearly the same memory bandwidth with an
economical 256-bit interface as it would by
building a much more expensive 512-bit bus
into its GPU.
Nvidia’s professed ambivalence toward
GDDR5 hasn’t stopped a third major
memory manufacturer—Qimonda—from
joining Hynix and Samsung in the market
for GDDR5 memory. Hmm, is anyone taking
bets that Nvidia’s next-generation GPU will
tap GDDR5?
AUTOPSYSonos ZonePlayer ZP120
The newly updated streaming box adds 802.11n support to its original
kick-ass chassis, but what else lies under the hood?http://www.maximumpc.com|OCT 08 |MAMAMAXIMXIMXIMXIMUUUUMMPPPCC| 71
SUBMIT YOUR IDEA Ever wonder what the inside of a power supply looks like?
Don’t take a chance on destroying your own rig; instead, let us do the dirty
work. Tell us what we should crack open for a future autopsy by writing to
[email protected].CPU
This board contains the
ZonePlayer’s CPU and Wi-Fi
adapter—it supports 802.11n
as well as b and g. The CPU
is shielded on both sides
of the board to reduce
potential interference
and noise from the
amp, which lies
directly below.HIGH-POWER TRANSISTORS
These MOSFETs are designed to handle
high-power requirements with good ef-
fi ciency at low voltages. They get hot, so
Sonos clips them directly to the alumi-
num frame of the chassis for maximum
passive cooling.POWER SUPPLY
These inductors and capacitors
form a resonant tank circuit.
Energy is exchanged between
these components in an oscil-
latory fashion, which allows
the device to precisely regulate
the amount of energy that’s
converted from the alternating
current supplied by your wall
jack to the direct current the
electronics require.AMPLIFIER
These two modules power the left and
right audio channels. They create a
high-frequency waveform which is then
low-pass fi ltered, which delivers smooth
audio output at the speaker terminals.