AMD ingnots, sliced "TBread" with the crusts cut off

CPU by KeithSuppe @ 2003-05-25

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!

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Tbred slices without the crust

Finally pertaining to the article's title; Tbred slices with the crust cut off. I want thank antipop at Xtremesys for his scrutiny. He described the ID process as "nonsense", and this is where being open minded is key. Instead of vehemently defending a moot point, I decided to investigate further, based his next (criticism) question:
"One last question, it's about the place on the wafer, you say that A and J are the closest to the center of the wafer, but I’ve never seen a Tbred B mark with a K or an R, what do they do with the chip on the border? Do they just put them in the bin?"

In this question lies the answer to the mystery. Yes, I believe do believe AMD "binned" the cores from those area's of the Wafer. Due to a possible lens misalignment, or some anomaly during the multiple Photolithographic/etching cycles, the outer wafer cores were rendered unusable. This is the section of Austin’s guide to which antipop was referring;
"The third line of code known as the stepping specifies the manufacturing process in reference to the wafer. These four letters are the four first letters of the TBred-B's; A > J > K > R. A being the highest quality, and indicative of those cores closest to the wafer center. A being the purist, and therefore capable of the highest speeds. So there are A TBreds and J Tbreds. However by AMDBoard article "There have not be any AIUHB Revision B's, so the next highest grade is the JIUHB", therefore all are JxxxB 1700+ Tbred-B's."

This would unambiguously explicate the JIUHB 1700's (and 2100's) propensity for 40% to 105% overclockability. I purport an anomaly in either the photolithographic lens alignment, or some other manufacturing anomaly rendered K - R outer areas of the wafer inutile. The high number of variables during manufacture, which can have detrimental effects on the end-product are as plentiful as dust particles in the air:
"During fabrication, any contaminants that land on a wafer -- the sheet of silicon that's the foundation for a chip -- can ruin the processors built on it. For example, a dust mote glowing in a beam of sunlight can damage hundreds or thousands of circuits. Even a smoke particle, measuring in at 0.5 microns, can short out a pair of lines in a nascent processor."
src: Byte.

This would certainly explain why the lower speed TBred's are capable of double overclocks, while the highest PR's aren't doing much better then 2.5GHz to 2.6GHz this under phase-change temps.. Certainly AMD utilizes their best cores for the upper end models. This theory would also explain WHY the small percentage of lower speed TBred's capable of 2.5GHz to 2.7GHz overclock's, commensurates perfectly with those of their counterparts (models 2400 and above). If AMD's Fab facilities are producing cores capable of such extraordinary overclock performance among the lower speed models, why aren't models 2400 and higher reaching 3.0GHz and above? Certainly the DUVL process hasn't been completely exhausted for AMD, ergo a ceiling has been reached. The fact Intel is surpassing 3.06GHz using standard Deep Ultraviolet Lithography, implies the problem with AMD lie somewhere else. It would be naive to think AMD wouldn't want their PR's 2400 and above capable of 2.7GHz overclocks, because this would simply is the basis for 3600 or 4000 PR processors. Even the experts were befuddled with the Tbred-B. I knew something was amiss when Ed Stroglio ( began identifying these as "Low end / High end" Thoroughbreds. It seems even Austin subscribed to A - J vs K - R as a means of determining performance:
"From our personal findings, the purity of the centre wafer will determine the high end model of a CPU. Higher end models are then called an A Thoroughbred while the lower end one is called the J Thoroughbred. AMD even had produced R Thoroughbred and K Thoroughbred for Revision A. But so far they do not exist in Revision B."

All one need do is empirically verify the data for them-self. Either recording overclocks from signatures, or revisiting as many threads on the topic (overclocking 1700's, or 2100's)
as they care to examine. Irregardless, I do not think it coincidental the highest overclock achieved by the fastest Thoroughbred, is equal to the highest overclock achieved by the slowest Thoroughbred. There's something missing, and that is those outer wafer cores. Ergo the "crusts cut off the Tbread". Pardon the pun.

I want to thank everyone whom contributed by printing their full sticker code, and especially thank Austin @ Without such experts (enthusiasts) willing to take risks sharing their hypotheses, this would be a boring hobby.

An update to this article, after initial reactions were posted on different forums, can be read here


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