Recently AMD enthusiasts (overclockers) have had a smile across their faces the length of which must have wifes and girlfriends wondering. Their new-found mistress; "lower-speed" Thoroughbred-B's, and their "double overclock" potential. Almost mythical in overclocking circles (prior to phase-change cooling) doubling a processor's default speed is the apotheosis for the enthusiast. So where did these sweethearts come from? And why have I chose the title "AMD ingots sliced "TBread" with the crusts cut off"? Buckle up, it's going to a bumpy ride!An update to this article, after initial reactions were posted on different forums, can be read here
For those of you not familiar with microprocessor fabrication I'll give a brief description, and you'll see it's pertinent. The silicon wafer, from which processor cores are cut, begins life as "...a purified polycrystalline silicon...first melted, then encouraged to crystallize into long cylinders, called ingots." This is actually a growth process taking a "seed crystal" which is submersed in a bath of molten silicon, and when the seed is slowly pulled up, the Ingot forms. These ingots are then sliced into "wafers" 300mm or 12" diameter. Next the wafer is polished on one side to a mirror perfect surface, there cannot be a flaw in this surface. Next a photo-resist or photo sensitive chemicals cover the wafer which is imprinted with the microcicuirty pattern as ultraviolet light shown through a stencil (or mask, there are multiple masks for each IC layer) leaves the image behind. "...the remaining photo resist is removed, leaving a pattern of silicon dioxide on the silicon wafer. Additional materials, such as poly-silicon, which conducts electricity, are deposited on the wafer through additional lithography and etching steps. Each layer of material has a unique pattern.
Together, they will form the chip's circuitry in a three-dimensional structure." The photo mask or stencil (which becomes the template for the design) costs approximately $1 million to $6 million to produce. Lithographic equipment itself weighs upwards of 20 tons, and cost $17 million. The cost a modern "Fab" plant runs approximately $1.6 billion. The costs are very high, and these figures pertain to a fab plant built to accommodate one core design. For this reason, it is often the case multiple processor speeds are produced exploiting the design parameters to obtain the highest possible speeds given the core's architecture. It's not that AMD doesn't WANT to make faster CPU's it's just that there are metaphysical limitations, given the current fabrication technology.
And as we surpass the 157nm process (.13 micron) traditional photolithographic methods are reaching their limits. When using a .13 micron chip, this is the measurement across etched lines in core architecture along which electrons travel (bytes/bits). The smaller the gate width, faster the processor speed and lower voltages. Using a process known as EUVL (Extreme Ultraviolet Lithography) a process by which the light waves which were once used to imprint down to .13 microns across, can now be shortened to ten times as small. And simply stated, processors will soon be ten times as fast! It's estimated by 2007 there will be 30GHz processors in your PC. EUVL uses light waves so short lenses are now obsolete, in fact 90% of the light would be absorbed unless the process takes place in a vacuum, and utilizes coated mirrors to bend or focus image into the wafer.
This is not science fiction, in 2001 at Scandia national Laboratories, a prototype EUVL machine successfully demonstrated the technology. Recently Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory and Sandia National Laboratories collaborating as the Virtual National Laboratory, successfully transferred the EUVL technology under a multi-year CRADA (Cooperative Research and Development Agreement) to the Extreme Ultraviolet Limited Liability Company (EUV LLC), a consortium headed by Intel Corporation that includes chipmakers Advanced Micro Devices, IBM, Infineon, Micron Technologies and Motorola. (Tech Space Feb 12, 2003) There's even a more promising technology LADI (Laser Assisted Direct Imprinting) utilizing a excimer laser, developed at Princeton which I won't go into, suffice it to say it has an even greater potential then EUVL. And it circumvents the 300 or so steps which make Lithographic, wafer fabrication exuberantly costly.
The reason I've explained microchip fabrication, in such detail, and with an emphasis on cost, is to exemplify the propensity, for error, and the ad hoc cost control.