Dynamic error handling for on-chip memory structures
A memory structure is provided that controls the activation of error handling bits as a function of operating voltage. In this way, error correction can be used to offset errors when the memory structure is run at low voltage (and frequency). However, negative performance impacts for such error correction, such as additional access latencies, can be avoided when the memory structure is run at higher voltage (and frequency) and memory errors are less likely. In addition, increased latencies due to evaluating error handling bits may be hidden by reading digital data bits from the memory structures speculatively and assuming no errors. Also, certain portions of memory structures may have larger cells, and therefore larger areas, than other portions, which may provide not only higher reliability at low operating voltages, but also faster operation with reduced latency.
1. A memory system comprising a series of addressable transistor memory cells holding digital data when powered by an operating voltage, wherein
the addressable transistor memory cells are grouped into at least two portions, each portion adapted for storing digital data bits and error handling bits for evaluating presence of errors in the digital data bits of the respective portion, and
wherein the error handling bits are evaluated for presence of errors in the digital data bits of a respective portion when there is a reduction in operating voltage, and the error handling bits are not evaluated for presence of errors in the digital data bits in the respective portion when there is not a reduction in operating voltage.
2. The memory system of claim 1 , wherein the portions provide different architectures having different predetermined susceptibility to errors as a function of operating voltage, whereby individual portions may be deactivated or activated with changes in operating voltage according to the predetermined susceptibility to errors as a function of operating voltage.
3. The memory system of claim 2 , wherein portions having lower susceptibility to errors as a function of operating voltage store greater amounts of error handling bits than portions having higher susceptibility to errors as a function of operating voltage.
4. The memory system of claim 2 , wherein the transistor memory cells of each portion differ according to area of an integrated circuit associated with transistors of each memory cell with the portions having a greater area being less susceptible to errors as operating voltage decreases than memory portions having lesser area.
5. The memory system of claim 4 , wherein corresponding individual transistors of the memory cells of each portion have different sizes of transistor area.
6. The memory system of claim 5 , wherein portions having greater sizes of transistor area are accessible with less latency than portions having lesser sizes of transistor area.
7. The memory system of claim 1 , wherein the error handling bits comprise error correcting code bits.
8. The memory system of claim 1 , wherein the error handling bits comprise redundant memory bits.
9. The memory system of claim 1 , wherein the memory cells are static random access memory cells.
10. An integrated circuit comprising:
a memory structure providing multiple independently controlled groups of memory cells, wherein the groups of memory cells are adapted to store digital data bits and error handling bits for evaluating presence of errors in the digital data bits of the respective group; and
a memory controller communicating with the memory structure to:
(a) monitor an operating state of the integrated circuit to determine an operating voltage; and
(b) evaluate the error handling bits for presence of errors in the digital data bits of a respective group when there is a reduction in operating voltage, and not evaluate the error handling bits for presence of errors in the digital data bits of the respective group when there is not a reduction in operating voltage.
11. The integrated circuit of claim 10 , wherein the groups of memory cells have predetermined differing susceptibility to errors as a function of operating voltage, and wherein the memory controller communicates with the memory structure to selectively activate and deactivate groups of memory cells as a function of operating voltage according to the predetermined differing susceptibility to errors as a function of operating voltage.
12. The integrated circuit of claim 11 , wherein groups of memory cells having lower susceptibility to errors as a function of operating voltage store greater amounts of error handling bits than groups of memory cells having higher susceptibility to errors as a function of operating voltage.
13. The integrated circuit of claim 11 , wherein the memory cells of the groups differ according to area of the integrated circuit associated with transistors of each memory cell with the groups having a greater area being less susceptible to errors as operating voltage decreases then memory cells of groups having lesser area.
14. The integrated circuit of claim 13 , wherein corresponding individual transistors of the memory cells of the groups have different sizes of transistor area.
15. The integrated circuit of claim 10 , wherein the error handling bits are at least one of error correcting code bits and redundant memory bits.
16. The integrated circuit of claim 10 , wherein the memory structure is at least one of a scratchpad random access memory, a physical register file, an instruction queue and a load/store queue.
17. An integrated circuit comprising a processor and a memory structure operable to communicate with the processor, wherein the memory structure includes multiple independently controlled groups of memory cells, wherein the groups of memory cells differ according to amounts of integrated circuit area associated with transistors of each memory cell with groups having a greater area being accessible with less latency than groups having a lesser area, the integrated circuit executing a program stored in a non-transient medium on the processor to:
(a) selectively deactivate a group of memory cells with a lesser amount of area than another group of memory cells with greater amount of area, wherein the group of memory cells with the greater amount of area provides faster operation than the group of memory cells with the lesser amount of area; and
(b) prioritize a first thread of the program for execution over a second thread of the program for execution, wherein the second thread of the program for execution is determined to require less memory than the first thread of the program for execution.
18. The integrated circuit of claim 17 , wherein each group of memory cells is adapted to store digital data bits and error handling bits for evaluating presence of errors in the digital data bits of the respective group, and wherein the integrated circuit executes to process digital data bits stored in a first group of memory cells, then subsequently evaluate error handling bits for presence of errors in the digital data bits of the first group.
19. The integrated circuit of claim 17 , wherein the groups of memory cells provide different architectures having different predetermined susceptibility to errors as a function of operating voltage, whereby individual groups of memory cells may be deactivated or activated with changes in operating voltage according to the predetermined susceptibility to errors as a function of operating voltage.
20. The integrated circuit of claim 19 , wherein portions having lower susceptibility to errors as a function of operating voltage store greater amounts of error handling bits than portions having higher susceptibility to errors as a function of operating voltage.