Intel Demos Core 2 Extreme QX9650 Quad-Core At IDF

MojoKid writes "Intel demonstrated a dual socket gaming rig at IDF this week, based on their Skulltrail platform with the X38 chipset. The interesting thing about this machine wasn't just that it had 45nm quad-core CPUs in its sockets, as well as PCI Express 2.0 capable slots, but also that it was running a pair of NVIDIA graphics cards in SLI. That's right, SLI on an Intel chipset. No word whether or not X38 would officially be supported with SLI just yet. In fact, NVIDIA representatives noted Intel was buying NVIDIA nForce 100 SLI Southbridges just for this one Intel motherboard model."

Comments

Re:Fans

[Sczi]

Unless it's so fat that the exhaust velocity drops low, backs up gas in the pipe, and actually *creates* backpressure. You could also have so much cam overlap that you need some backpressure to make the air/fuel stay in the cylinder while waiting for the exhaust valve to close. Everything in moderation, friend, especially stickers, wings, and fart cans.

Re:Fans

[DigiShaman]

Larger is not always better. All engines have a sweet spot in regards to excaust flow. Too small of a pipe diameter, and you run into restriction. To large, and you're not tapping into the scavenge effect.

Due to some active-x plugin, I will cut-and-past from the miata.net page.

OK, so here is Backpressure 101.

The purpose of the car's exhaust system is to evacuate gases from the combustion chamber quickly and efficiently. The exhaust gasses do not flow in a smooth stream. Because the gasses are vented at each opening of the exhaust valves there is a pulse of gasses from each cylinder. Just put you hand near the exhaust tip and you will feel the pulses. In a MX-5 engine there are four pulses per cycle (except if it's John Pitt's supercharged V8 then there are eight really big pulses per cycle).

The exhaust gasses produce a positive flow in the exhaust pipe. Backpressure can be likened to resistance to the positive flow of the exhaust stream. Taken to its extreme backpressure can lead to a reversal (albeit momentarily) of the exhaust stream.

Is Bigger Better or is Faster Best?

When contemplating a modified exhaust system there are those who want the biggest diameter pipe that can be had. Their idea must be that fatter pipes are more effective at venting than narrower pipes. This sounds reasonable but it is not quite correct. Sure wider pipes have greater volume and higher flow capacity, but that is just half of the story. Capacity is one consideration but gas velocity is the other factor.

An experienced exhaust designer knows that the best exhaust is one that balances flow capacity with velocity. A given volume/time of gasses will travel faster through a 2" pipe than the same volume of gas passing through a 3" pipe. So when taken to its extremes we can see that a too narrow pipe will create backpressure (restrictions to positive flow) problems and a too wide pipe will cause a very slow flow with no backpressure.

The optimum is where the fastest velocity is achieved with the least constriction possible.

This situation will arise when the pipe is wide enough so that there is the least level of positive backpressure possible whilst achieving the highest exhaust gas velocity.

The faster the exhaust gas pulse moves, the better it can scavenge out all of the spent gasses during valve overlap. The scavenge effect can be visualised by imagining the high-pressure pulse with a trailing low-pressure area behind. The faster the high-pressure pulse moves the stronger the draw on the low-pressure gasses and the gasses behind that. The scavenge action is like (but not exactly) suction on the gasses behind.

The greater the clearance burned fuel from the combustion chamber the less diluted the incoming air/fuel mix is. Scavenging can also aid intake on overlapping valves (where the exhaust and inlet valves are open at the same time) by drawing in the intake. These are good things to happen.

So instead of going for the widest pipe possible we should be looking for the combination of the narrowest pipe that produces the least backpressure possible. In this scenario we achieve the least restriction on positive flow and the highest gas travel speed.

Exhaust pipe diameters are best suited to a particular RPM range. If we used a constant RPM engine this would be easy to specify. But a variable RPM engine will mean that not one size suits all. It is possible to vary the size of exhaust volumes according to rpm but it is very expensive (Ferrari has done it). The optimum gas flows (volume and speed) are required at the RPM range that you want your power band to be located. For a given engine configuration a small pipe diameter will produce higher exhaust velocities at a low RPM (good) but create unacceptably high amounts (bad) of backpressure at high rpm. If you had a car with a low RPM power band (2,000-3,000 RPM) you would want a narrower pipe than if your power band is located at 5,000-7,000 RPM.

Re:Fans

[petsounds]

Although rice rockets are the modern equivalent, this kind of looks-over-performance started back in the '50s during the custom car craze. The Beach Boys wrote a song about it called "No-Go Showboat":

"Well the engine compartment's filled with all chrome goodies
In my no-go showboat (no-go showboat)
Yeah but everybody takes me even old Ford woodies
In my no-go showboat (no-go showboat)
When it comes to speed, man, I'm just outa luck
I'm even shut down by the ice cream truck
'Cause it's a no-go showboat (no-go showboat)"

Of course, at least back then the posers cared enough to use nice-looking parts. Rice rockets these days just use whatever $2 part looks like it might fit.