"Jeff Liebermann" wrote in message
...
On Tue, 31 Aug 2010 01:26:23 +0100, "Arfa Daily"
wrote:
Have you any idea just how much processing power it takes to run a
user-interactive story in real time, and then to 3D render the graphics in
real time ?
Well, no. I'm not a power user. What little rendering I do is with
bacon fat.
Do you think that they rate the 12v PSU for 23.5 amps in one
version, and 32 amps in the other, for fun ? Those are not real questions,
because I know full well when you stop and think about it, you know the
answers, Jeff.
Actually, I don't know. I don't have any customers with such machines
and have had zero experience with high power graphic workstations
(other than early 1980's Applicon CAD stations) or game machines. I
have worked on various network servers, which do burn such power
levels. I have looked at a 3D MRI image processor, which had some
manner of dedicated processor inside, but it certainly wasn't belching
400 watts of heat (my estimate by the amount of fan noise).
I've just looked at the rating plate on the bottom of one of the cases,
and
it is 240v (nominal UK line voltage) at 1.8 amps. I make that a maximum
input power of around 430 watts. It's a switching PSU, so I reckon that we
can rate that as being at the very worst 80% efficient, so that's still
345
watts potentially going somewhere. I'm prepared to go with 45 watts into
ancillary circuitry on the board, which still leaves around 300 watts
going
somewhere. Perhaps I'm being naive, but my best guess is that it's
disappearing into the two bloody great BGAs which the manufacturers are
trying their utmost to heatsink. If you try to run one of these machines
with the heatsinking not in place, it goes into thermal protect in about 5
seconds - and all it's doing then is booting. The heatplates on the BGAs
are
at this point hot enough to take your fingerprints off ...
Nope, I'm pretty sure that these two puppies are good for 150 watts
apiece,
when the machine is doing some real work.
Ok, I stand corrected. I've been assuming that the CPU's are doing
most of the power dissipation. I didn't think of a dedicated graphics
processor or whatever the BGA chips are doing. Do you have a gun
style IR thermometer? I use that to determine if anything is running
hot. I use a black (non-reflective) cardboard tube attached to the
lens to prevent it from picking up adjacent components. Incidentally,
I have yet to find one where the laser dot actually points to where
the device is measuring when in close proximity. You can also get a
rough idea of how much effort is going into cooling. If the BGA's
burn more power than the CPU's, then they're going to need more
massive heat sinks and better air cooling. At 400 watts, I would
think they would have gone to heat pipes and external radiators or
maybe liquid cooling.
Incidentally, I repaired a P4 motherboard yesterday which used Artic
Silver. My guess is that there was about 5 times as much Artic Silver
smeared over the CPU (and down the sides where it does nothing) as
necessary. The stuff down the sides was still fluid, so at $10 for
3.5 grams, I saved the excess.
--
Jeff Liebermann
Skype: JeffLiebermann AE6KS 831-336-2558
All of the processing power is in those two BGAs Jeff. They *are* the
processors. One is a dedicated engine that runs the game (or plays a BluRay
disc), as well as handling all the disc I/O - optical and hard - and
internet / network access. On top of this, it manages all of the
housekeeping tasks, so it's doing a lot of work, especially when it's
actually running a game. Modern games have come a long way since the days of
Doom. Most maintain a highly complex 3D 'reality' in which the game is set,
and the gameplay takes place. Just consider for a moment, the highly complex
calculations that have to go on, to work out how potentially many actions
all at once, interact with the 3D model, and the knock-on effects that these
might have on both the gameplay and the graphical environment. And remember
that this is taking place in real time. The second BGA is a dedicated
graphics engine. Again, consider how these games now look. Most are quite
close to reality, and some scenes would have you hard pressed to tell if you
were looking at a photo, or a piece of virtual reality. Given all that, just
imagine the billions of calculations that are going on, again in real time,
to work out the texturisation and surface rendering of all the visible
objects, and how the light and shadows interact with those objects as they
move within the scene. It really is mind-boggling just how sophisticated all
of this is now. I can recall 25 years ago when I worked on high-end graphics
systems, rendering the famous 3D conch shell image took a dedicated graphics
terminal, hosted by a VAX mainframe, around 20 minutes. That's one image,
not moving. Now think about a moving HD image in an HD background in real
time. That's a LOT of processing power, needing a lot of amps to perform ...
The fan on these things *is* large, as is the heatsinking assembly, and when
the processor finally decides to ramp the fan up, it sounds like a vacuum
cleaner. For this reason, at idle they tend to run it at below what I would
consider a 'sensible' minimum, exacerbating the thermal stresses on the
chips, their (lead-free) soldering, and the board to which they are
attached.
Arfa