Lowering voltage for cache memory operation
First Claim
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1. A method of operating a cache comprising volatile memory cells in a mobile processor system, the method comprising:
- determining a first voltage value as a minimum operating voltage (Vcc min) of the cache if each of the volatile memory cells functions correctly when the first voltage value is set as Vcc min;
setting a Vcc min of the cache to a second voltage value at which the number of volatile memory cells that fail in the cache is between approximately 0.1% and approximately 1% of the number of lines in the cache, while the remaining volatile memory cells continue to function correctly at the second voltage value chosen for Vcc min; and
compensating for errors produced by volatile memory cells in the cache that fail when operated at the second voltage value chosen for Vcc min to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value.
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Abstract
Setting a minimum operating voltage (Vcc min) of the cache to a voltage value at which the number of cells that fail in the cache is between approximately 0.1% and approximately 1% of the number of lines in the cache, while the remaining cells continue to function correctly at the voltage value chosen for Vcc min, and compensating for errors produced by memory cells in the cache that fail when operated at the voltage value chosen for Vcc min.
34 Citations
30 Claims
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1. A method of operating a cache comprising volatile memory cells in a mobile processor system, the method comprising:
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determining a first voltage value as a minimum operating voltage (Vcc min) of the cache if each of the volatile memory cells functions correctly when the first voltage value is set as Vcc min; setting a Vcc min of the cache to a second voltage value at which the number of volatile memory cells that fail in the cache is between approximately 0.1% and approximately 1% of the number of lines in the cache, while the remaining volatile memory cells continue to function correctly at the second voltage value chosen for Vcc min; and compensating for errors produced by volatile memory cells in the cache that fail when operated at the second voltage value chosen for Vcc min to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method in a mobile processor system, the method comprising:
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in a cache, the cache further comprising volatile memory cells, determining a first voltage value as a minimum operating voltage (Vcc min) for the cache if each of the volatile memory cells functions correctly when the second voltage value is set as Vcc min; setting Vcc min of the cache to a second voltage value that exceeds an estimate of the mean (M) of the operating voltages at which the volatile memory cells fail by between approximately 3.7 and 4.7 times an estimate of the standard deviation (SD) of the operating voltages at which the volatile memory cells fail (M+approximately 3.7*SD<
=Vcc min<
=M+approximately 4.7*SD); andcompensating for errors produced by volatile memory cells in the cache that fail when operated at the second voltage value chosen for the minimum operating voltage using a single bit error correcting code (ECC) unit to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value; compensating for soft errors in volatile memory cells caused by radiation using the ECC unit; and producing and storing a signature comprising an indication of the volatile memory cells that fail in the cache. - View Dependent Claims (10, 11)
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12. A processor comprising:
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a cache comprising volatile memory cells; a voltage source to determine a first voltage value as a minimum operating voltage (Vcc min) of the cache if each of the volatile memory cells functions correctly when the second voltage value is set as Vcc min, and to set Vcc min of the cache to a second voltage value at which the number of volatile memory cells that fail in the cache is between approximately 0.1% and approximately 1% of the number of lines in the cache, while the remaining volatile memory cells continue to function correctly at the second voltage value chosen for Vcc min; and error compensation logic to compensate for errors produced by volatile memory cells in the cache that fail when operated at the voltage value chosen for Vcc min to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A processor comprising:
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a cache, the cache further comprising volatile memory cells, a voltage source to determine a first voltage value as a minimum operating voltage (Vcc min) of the cache if each of the volatile memory cells functions correctly when the second voltage value is set as Vcc min, and to set a Vcc min of the cache to a second voltage value that exceeds an estimate of the mean (M) of the operating voltages at which the volatile memory cells fail by between approximately 3.7 and 4.7 times an estimate of the standard deviation (SD) of the operating voltages at which the volatile memory cells fail (M+approximately 3.7*SD<
=Vcc min<
=M+approximately 4.7*SD);an error correcting code (ECC) unit to compensate for errors produced by volatile memory cells in the cache that fail when operated at the voltage value chosen for the minimum operating voltage, to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value, and to compensate for soft errors in volatile memory cells caused by radiation using the ECC unit; and syndrome logic to produce and store a signature comprising an indication of the volatile memory cells that fail in the cache. - View Dependent Claims (21)
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22. A system comprising a processor, the processor comprising:
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a cache comprising volatile memory cells; a voltage source to determine a first voltage value as a minimum operating voltage Vcc min of the cache if each of the volatile memory cells functions correctly when the second voltage value is set as Vcc min, and to set a Vcc min of the cache to a second voltage value at which the number of volatile memory cells that fail in the cache is between approximately 0.1% and approximately 1% of the number of lines in the cache, while the remaining volatile memory cells continue to function correctly at the second voltage value chosen for Vcc min; and error compensation logic to compensate for errors produced by volatile memory cells in the cache that fail when operated at the voltage value chosen for Vcc min to enable operation of the mobile processor system at a reduced Vcc min equal to the second voltage value that is less than the first voltage value. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30)
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Specification