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What is "wafer integrity"
- Thread starter c627627
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- Feb 4, 2003
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Okay, I think I've had a eureka moment here. I've looked over my previous evidence, and I think I've got an explanation that all makes sense.
http://www.amdforums.com/showthread.php?threadid=213028&perpage=15&highlight=gameve&pagenumber=8
If you look closely, you'll notice that these do very well at below 1.7v or so, but once you get higher, things begin to fall apart. Several needed 1.8v to reach only 2.3ghz. At lower voltages, they do better, but begin to do progressively worse at higher ones. So, at below 1.7v, the TPXW's do as well, if not better than any, but at higher ones, do a lot worse than most. My friend has one of these, in fact, and an SK6+. It can't even do 2.3ghz, no matter what. If it were an M or higher, then it would have been able to clock higher as more voltage was put in. The diminishing returns were too heavy on this one; it can't take the higher temperatures caused by the voltage. Now, my UPMW, which I have tested under an SK6+ myself went about 100mhz higher than his with identical cooling and voltage; 2369mhz.
This could explain this:
So as we can clearly see, having higher wafer quality does not always equate to higher overclockability. In some cases it can, in some cases it can hurt. OC Detective hypothesizes that those with lower third letters need a higher stock voltage. If they need higher voltages to sustain lower speeds, then in theory, they should end up being able to sustain higher voltages overall, and perhaps, end up ahead of those with lower third letters in some cases. To take this a step further, this can potentially explain why the M's that are most common do so well. They are a sort of compromise between needing high voltages and not being able to sustain them. With this in mind, it makes perfect sense that these are the overclocker's choice. But are they the choice for all overclocks? The highest overclocks in the VR-Zone database have lower third letters across the board. They all use extreme forms of cooling in which a heavily overvolted processor can thrive, provided that in can sustain these voltages. So when pushed to the limits, these higher wafer integrity processors with lower letters do the best, but with lower forms of cooling can potentially do the worst. With the mid-level cooling that most of us have, the middle is what works the best. I may be thinking far out, but you have to admit, it does make plenty of sense
.
http://www.amdforums.com/showthread.php?threadid=213028&perpage=15&highlight=gameve&pagenumber=8
If you look closely, you'll notice that these do very well at below 1.7v or so, but once you get higher, things begin to fall apart. Several needed 1.8v to reach only 2.3ghz. At lower voltages, they do better, but begin to do progressively worse at higher ones. So, at below 1.7v, the TPXW's do as well, if not better than any, but at higher ones, do a lot worse than most. My friend has one of these, in fact, and an SK6+. It can't even do 2.3ghz, no matter what. If it were an M or higher, then it would have been able to clock higher as more voltage was put in. The diminishing returns were too heavy on this one; it can't take the higher temperatures caused by the voltage. Now, my UPMW, which I have tested under an SK6+ myself went about 100mhz higher than his with identical cooling and voltage; 2369mhz.
This could explain this:
So as we can clearly see, having higher wafer quality does not always equate to higher overclockability. In some cases it can, in some cases it can hurt. OC Detective hypothesizes that those with lower third letters need a higher stock voltage. If they need higher voltages to sustain lower speeds, then in theory, they should end up being able to sustain higher voltages overall, and perhaps, end up ahead of those with lower third letters in some cases. To take this a step further, this can potentially explain why the M's that are most common do so well. They are a sort of compromise between needing high voltages and not being able to sustain them. With this in mind, it makes perfect sense that these are the overclocker's choice. But are they the choice for all overclocks? The highest overclocks in the VR-Zone database have lower third letters across the board. They all use extreme forms of cooling in which a heavily overvolted processor can thrive, provided that in can sustain these voltages. So when pushed to the limits, these higher wafer integrity processors with lower letters do the best, but with lower forms of cooling can potentially do the worst. With the mid-level cooling that most of us have, the middle is what works the best. I may be thinking far out, but you have to admit, it does make plenty of sense
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Gautam, did that link have a desription of what exactly wafer integrity is? I have tried opening it but I get an object not found error? I think that if we could get someone with extreme cooling to test two chips (one with the letter A and one with the letter M) we would be a lot closer to finally uncovering this letter's relevance to all overclockers and not just those of use who use standard air or water cooling. As for the TPXW I would really like to see more overclock info on that before we can make any firm decision as one result is insufficient to provide any conclusion - especially as the bottleneck on his system maybe elesewhere.
I do not know what wafer integrity refers to. There are process variations of a given silicon manufacturing process, as any manufacturing process. As a result, the intrsinic silicon proporties, such as transistor channel length and width, gate oxide thickness, silicon carrier doping, transistor threshold voltage, leakage current, ..., of a wafer vary to certain extent (sigma variation). As further scaling down, statistical variation comes into play, namely, nearby transistors in the same chip/wafer can behave differently.
A more interesting question is what the implications of these wafer properties of lower threshold voltage and shorter channel length due to process variation of a manufacturing process are, as I suspect for the the Tbred B DLT3C. It is being rated at lower Vcore but it can run faster than other Tbred B at same voltage. Even it is manufactured with 0.13 micron like other Tbred B, it is effectively behaving like a chip with less than 0.13 micron, resembling the future generation trend.
As the transistor size (channel length) of future generations of silicon chips are scaled down to, e.g., 90, 65, 45, ... nano-meter, the supply voltage, transistor channel length and threshold voltage will be lowered accordingly. Even the supply voltage is lower, the transistors run faster, both current and power density also increase (actual trend). As the transistors are scaled down, logic gate delay decreases, both the active power density (W/cm^2) and the passive leakage power density (both gate and subthreshold) increase. The passive component increases at an even faster pace.
For more details about the low voltage Tbred B 1700+, refer to
Why the 1700+ can run so fast at low Vcore?
A more interesting question is what the implications of these wafer properties of lower threshold voltage and shorter channel length due to process variation of a manufacturing process are, as I suspect for the the Tbred B DLT3C. It is being rated at lower Vcore but it can run faster than other Tbred B at same voltage. Even it is manufactured with 0.13 micron like other Tbred B, it is effectively behaving like a chip with less than 0.13 micron, resembling the future generation trend.
As the transistor size (channel length) of future generations of silicon chips are scaled down to, e.g., 90, 65, 45, ... nano-meter, the supply voltage, transistor channel length and threshold voltage will be lowered accordingly. Even the supply voltage is lower, the transistors run faster, both current and power density also increase (actual trend). As the transistors are scaled down, logic gate delay decreases, both the active power density (W/cm^2) and the passive leakage power density (both gate and subthreshold) increase. The passive component increases at an even faster pace.
For more details about the low voltage Tbred B 1700+, refer to
Why the 1700+ can run so fast at low Vcore?
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My own personal take on wafer integrity is that it is too vague a description/definition as to be of any impact. I tend to agree with you hitechjb1 we sould be looking at the benefits and detriments of these cpus which require less default votage and which typically overclock better irrespective of the greater leakage current they give out. I suspect that because AMD now have effectively a very stable manufacturing process and that variation is being minimised they are indeed effectively operating more often than not at lower than 0.13 micron.
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Link fixed. Whatever it may be, I think there's sufficient evidence to support lower letters needing more voltage, and scaling better with it, and lower letters the opposite. You cannot deny that there is much variation between AMD processors, even within weeks and specific five letter codes, etc. Where the variation is coming from for sure is anyone's guess.
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