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NTT Verifies Diamond Semiconductor Operation At 81 GHz
Anonymous Coward writes "This story over at eetimes.com reports of a semiconductor made of diamond that is able to run at 81 GHz." Mmmm, foreshadowing.
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81GHz is the switching speed of the transistor, not the processing speed of a resulting PC. Some of the reasons are:
* CPU's perform a large number of transistor switches in a single clock cycle.
* The rise/fall response time must be much smaller than the switching time.
Don't be uninformed...oh wait this is slashdot. Vacuum tubes are still used in RF broadcasting, especially digital TV because the are able to reach the power levels necassary to broadcast a 50kW radio signal at low enough distortion to cleanly transmit the digital signals.
This lengthy article gives a fascinating history into how the DeBeers cartel has created artificial scarcity in the diamond market and convinced the western world that a "Diamond is Forever". Before the 19th century, no one ever had to spend 6 weeks salary on an engagement ring!
Because you have to run those signals over wires, which do a really crappy job of conducting a high speed signal. On chip cache is certainly fast - just expensive (real estate and fabrication errors)
At the sort of frequencies we're currently using, circuit tracks look more like inductors and capacitors than bits of wires. They essentially act as antennas, and there is a massive amount of effort spent in trying to avoid those effects.
One reason which another poster mentioned is the data transfer over the bus between the CPU and Main Memory, this is usually a few inches which means the signal can take more than 10ns to travel along the bus (which is a significant amount of time in chip design).
Another reason is that SRAM is used in a CPU for cache - its VERY fast but takes up more silicon per bit and is very expensive per bit.
Main memory is generally made of DRAM which is slower but also much smaller so you can get a much larger amount of memory onto a chip and much cheaper.
It's not that the latest technology isn't used in memory, it's just that its very expensive so it's used within the CPU as a cache while main memory will be slower in order to balance space vs cost for the machine to still be both affordable and usable.
Once the price drops, the cache technology gets put into main memory and a newer faster one replaces it in the cache.
The other big thing is that most of the advances in CPU speed are not due to the chip tecnology but due to design, especially pipelining.
CPUs go through a series of stages (eg fetch-read-execute) and the CPU can take advantage of this by running each stage while the next stage is still running.
This trick can't be taken advantage of in memory as memory does not contain several stages - hence pipelining increased cpu speed by something in the region of 5-10x while not increasing memory speed at all.
It's mainly new design tricks like this that have made most of the speed advances, which is why processor speed increases at such a larger rate than memory speed.
Negative; the GM operation was shut down because all they could produce cheaply with their hydraulic presses was diamond powder. They actually were to the point where they could make contiguous crystalline structures bigger than dust; however, the cost far exceeded that of the DeBeers extortion and international crime fee diamonds. Though GM abandoned the project for purely financial reasons, I'm sure that DeBeers was happy about it nonetheless.