Leveraging chip variability
Embodiments are described that leverage variability of a chip. Different areas of a chip vary in terms of reliability under a same operating condition. The variability may be captured by measuring errors over different areas of the chip. A physical factor that affects or controls the likelihood of an error on the chip can be varied. For example, the voltage supplied to a chip may be provided at different levels. At each level of the physical factor, the chip is tested for errors within the regions. Some indication of the error statistics for the regions is stored and then used to adjust power used by the chip, to adjust reliability behavior of the chip, to allow applications to control how the chip is used, to compute a signature uniquely identifying the chip, etc.
1. A chip comprising:
a region-specific error profile configured to indicate reliability traits of respective regions of the chip according to a given operating parameter value, the region-specific error profile configured to provide reliability traits of a given region as a function of respective different values of the operating parameter value;
the region-specific error profile further configured to obtain first indications of respective reliabilities of the regions according to a first target operating parameter value and to obtain second indications of respective reliabilities of the regions according to a second target operating parameter value; and
a first set of the regions selected based on the first indications of the respective reliabilities, and a second set of the regions selected based on the second indications of the respective reliabilities; and
the first and second sets of selected regions being made available or unavailable based on the selection thereof.
2. A chip according to claim 1 , wherein the region-specific error profile was derived by measuring errors on the chip that occurred at different levels of an error-sensitive factor.
3. A chip according to claim 2 , wherein the chip comprises cells, and wherein the error-sensitive factor comprises a physical aspect of the chip whose variation directly affects the probability that the cells of the chip will incorrectly store values.
4. A chip according to claim 3 , wherein the error-sensitive factor comprises temperature, power, clock rate, or voltage.
5. A chip according to claim 1 , wherein the first and second set of regions are made unavailable by a memory controller of an operating system executing on a computing device that comprises the chip.
6. A chip according to claim 5 , wherein the rate of power consumption of the chip is reduced in association with making the regions unavailable.
7. A chip according to claim 6 , wherein the rate of power consumption is reduced by altering a refresh rate or voltage of the chip.
8. An apparatus comprising:
a chip;
a region-specific error profile stored by the apparatus, the region-specific error profile, when the apparatus is operating, configured to indicate reliabilities of respective regions of the chip;
a memory controller that, when the apparatus is operating, is configured to obtain, from the region-specific error profile, indications of the respective regions, the indications corresponding to respective reliabilities of the regions; and
the memory controller, when the apparatus is operating, able to allocate memory from the regions according to the obtained indications of the respective regions, wherein the memory controller is configured to allocate memory according to target values of an operating factor to the region-specific error profile, the operating factor comprising a variable physical property of the chip, and wherein the memory controller is further configured to:
provide a first target value to the region-specific error profile and based on a correspondingly returned first set of indications of the regions perform a first region adjustment comprising adjusting which of the regions are available to from an operating system for storing data; and
provide a second target value to the region-specific error profile and based on a correspondingly returned second set of indications of the regions perform a second region adjustment comprising further adjusting which of the regions are available from the operating system for storing data.
9. An apparatus according to claim 8 , wherein the region-specific error profile is able to, when the apparatus is operating, indicate, for each region, region-specific reliabilities for respective operating values of an error-specific factor.
10. An apparatus according to claim 8 , wherein the memory controller comprises a component of an operating system.
11. An apparatus according to claim 10 , wherein the memory controller, when the apparatus is operating, is able to receive allocation requests for memory, the allocation requests indicating respective reliabilities of memory being requested, and wherein the memory controller satisfies the requests based on the indications of the respective regions of the chip.
12. An apparatus according to claim 8 , wherein the memory controller comprises a component of the chip.
13. An apparatus according to claim 8 , wherein the region-specific error profile was derived by testing the chip at different values of an error-sensitive factor, the error-sensitive factor comprising a factor that correlates with reliability of the chip.