Maximum Clock Rates in CPU Chips: Measuring Accuracy and Precision - Prof. Peter M. Chen, Study notes of Engineering

Download Maximum Clock Rates in CPU Chips: Measuring Accuracy and Precision - Prof. Peter M. Chen and more Study notes Engineering in PDF only on Docsity! Statistics Why haven’t we needed statistics so far in this class? Maximum clock frequency Is there a limit to how fast you can set the clock? plus1_outregister clock plus1ENGR 100 1 Peter Chen Speed binning of CPU chips CPU chips vary in the clock rate at which they can run, due to physical variations. E.g., some processor chips in a batch may be able to run at 3.4 GHz, others only at 3 GHz Chip manufacturers measure how fast each chip can run at and put them in bins Let’s say we’re measuring the maximum clock rate for a chip • try different clock rates, see if the chip works reliably on a set of programs • use a variable-speed clock generator to try different clock rates • clock generator has a speed dial, with marks every .05 GHz (2.40, 2.45, 2.50, 2.55, ... , 3.40) • e.g. measure the max clock rate of a particular chip as 3.15 GHz Two attributes of a measurement How accurate is this measurement? • how close is your measurement to the true number? • e.g. if true maximum clock rate for this chip is 3.16 GHz, you’re accurate to within .01 GHz How precise is this measurement? • how exactly did you measure it, i.e. to what level of detail? • what is the limit to precision with the above clock gener- ator? • is your precision guaranteed to be no worse than this?ENGR 100 2 Peter Chen