Read-modify-write memory using read-or-write banks

• US 6,804,162 B1
• Filed: 04/05/2002
• Issued: 10/12/2004
• Est. Priority Date: 04/05/2001
• Status: Expired due to Fees

• Current Assignee: T-Ram, LLC
• Original Assignee: T-Ram, Inc.
• Inventors: Eldridge, Matthew, Igehy, Robert Homan
• Primary Examiner(s): Nguyen, Van Thu
• Assistant Examiner(s): Luu, Pho M.
• Application Number:
  US10/117,501
• Time in Patent Office: 921 Days
• Field of Search: 365/230.03, 365/230.01, 365/230.06, 365/230.08
• US Class Current: 365/230.03
• CPC Class Codes: G06F 12/0893 Caches characterised by their organisation or structure
• CPC Class Codes: G06F 2212/3042 being part of a memory device, e.g. cache DRAM
• CPC Class Codes: G11C 2207/104 Embedded memory devices, e.g. memories with a processing device on the same die or ASIC memory designs
• CPC Class Codes: G11C 2207/2245 Memory devices with an internal cache buffer
• CPC Class Codes: G11C 7/1006 Data managing, e.g. manipulating data before writing or reading out, data bus switches or control circuits therefor
• CPC Class Codes: G11C 8/12 Group selection circuits, e.g. for memory block selection, chip selection, array selection

Abstract

Minimal memory access times are realized by using a single access to a read-modify-write bank. A read-modify-write memory including at least one read-or-write bank is operated in a manner that uses at most one access to each of the at least one read-or-write banks for each read-modify-write access to the memory during a memory cycle. The access can be effected during a single clock cycle and can be used for read, write and read-modify-write memory access.

Claims

1. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify-write access to the memory; and

wherein the read-modify-write bank has a cycle time that is smaller than the sum of the read cycle time and write cycle time of a slowest read-or-write bank in the memory arrangement, wherein the circuit arrangement is adapted to effect a read-modify-write cycle time that is smaller than the sum of the slowest read-or-write bank'"'"'s read cycle time and write cycle time.

2. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify-write access to the memory; and

wherein the at least one read-or-write bank includes a plurality of read-or-write banks and wherein the read-modify-write bank is adapted to be used as a cache for the plurality of read-or-write banks.

3. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify-write access to the memory; and

wherein the storage capacity of the read-modify-write bank is at least the storage capacity of the largest read-or-write bank.

4. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank;

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

at least one pipeline register adapted to store data;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify-write access to the memory; and

wherein the storage capacity of the read-modify-write bank is at least the storage capacity of a largest one of the read-or-write banks less the storage capacity of the pipeline registers.

5. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify -write access to the memory; and

wherein memory addresses in the circuit arrangement are partitioned into a bank address that identifies a particular read-or-write bank and a row address that identifies a particular word within the read-or-write bank.

6. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank and further comprising a read-modify-write bank electrically coupled to the at least one read-or-write bank; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle and adapted to provide control signals for effecting the at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory;

wherein the circuit arrangement is adapted to use at most one access to each said at least one read-or-write bank and only one access to the read-modify-write bank for each read-modify-write access to the memory.

7. A circuit arrangement for providing read-modify-write memory, the circuit arrangement comprising:

a memory having at least one read-or-write bank electrically coupled to a read-modify-write bank having a tag that indicates a read-or-write bank to which data in the read-modify-write bank belongs; and

control circuitry adapted for using at most one access to each said at least one read-or-write bank and one access to the read-modify-write bank, for each read-modify-write access to the memory during a single memory access cycle.

8. The circuit arrangement of claim 7, wherein, in response to a read-modify-write request for the read-or-write bank corresponding to the tag, the control circuitry is adapted to cause data from the read-modify-write bank to be read, modified and written back to the read-modify-write bank.

9. The circuit arrangement of claim 8, wherein the control circuitry is further adapted to cause the modified data to be written to the read-or-write bank corresponding to the tag.

10. The circuit arrangement of claim 7, wherein, in response to a read-modify-write request for a read-or-write bank that does not correspond to the tag, the control circuitry is adapted to cause data in the read-modify-write bank to be written to a read-or-write bank corresponding to the tag and to cause data from the read-or-write bank for which the read-modify-write request was made to be read, modified and written to the read-modify-write bank.

11. The circuit arrangement of claim 7, wherein the read-modify-write bank has a smaller cycle time than said at least one read-or-write bank.

12. The circuit arrangement of claim 7, wherein the read-modify-write bank includes a dual-ported bank adapted to allow a read and a write access on every data bank cycle.

13. The circuit arrangement of claim 7, wherein the read-modify-write bank includes two read-or-write banks augmented with a ping-pong bit per word.

14. The circuit arrangement of claim 13, wherein the ping-pong bit is adapted to indicate which of the two read-or-write banks has valid data to be read, the control circuitry being adapted to cause data to be written to one of the two read-or-write banks indicated as not having valid data to be read, and to toggle the ping-pong bit to indicate that the one of the two read-or-write banks that was written to has valid data.

15. The circuit arrangement of claim 7, wherein the tag has a read cycle time smaller than the sum of the read cycle time and write cycle time of the at least one read-or-write bank.

16. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including using a control circuit adapted to effect the read-modify-write access using at most one access to each said at least one read-or-write bank.

17. The method of claim 16, wherein using at most one access includes using at most one read access.

18. The method of claim 16, wherein using at most one access includes using at most one write access to each said at least one read-or-write bank for each read-modify-write access to the memory.

19. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including using at least one read-modify-write cache.

20. The method of claim 19, wherein using at most one access to each said at least one read-or-write bank includes using a plurality of read-or-write banks.

21. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including reading a word from a read-or-write bank that is adapted for destructive reading and writing the unmodified read word back into the read-or-write bank that it was read from.

22. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including error-correction of encoded words with partial word writes, the method further comprising;

reading an encoded word from the at least one read-or-write bank;

decoding the encoded word;

modifying the decoded word by inserting a partial word;

re-encoding the modified decoded word; and

writing the re-encoded word into the at least one read-or-write bank.

23. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including overlapping a read-modify-write cache access with the read-or-write bank access such that the read-modify-write cycle time is smaller than the sum of the slowest read-or-write bank'"'"'s read cycle time and write cycle time.

24. The method of claim 23, wherein overlapping the read-modify-write cache access with the read-or-write bank access includes using a pipeline register to store data during the read-modify-write access to the memory.

25. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle, including performing a late select that includes simultaneously effecting a read of the addressed read-or-write bank and a read of a tag that indicates which read-or-write bank'"'"'s data is in a cache, wherein data from the read-or-write bank is returned in response to the tag indicating that the data in the cache does not correspond to the addressed read-or-write bank and wherein data from the cache is returned in response to the tag indicating that the data in the cache corresponds the addressed read-or-write bank.

26. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

receiving an incoming address request;

reading a word from a row of a read-or-write bank corresponding to the incoming address;

reading a word from a row of a cache corresponding to the row of the read-or-write bank;

reading a tag of the cache that indicates which read-or-write bank'"'"'s word is contained in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, returning data from the cache for the read access; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, returning data from the read-or-write bank for the read access.

27. The method of claim 26, wherein the cache includes a read-modify-write bank.

28. The method of claim 26, wherein reading the tag includes reading the tag while reading the word from the row of the cache.

29. The method of claim 28, herein reading the word from the row of the read-or-write bank and reading the word from the row of the cache includes simultaneously reading the words from the read-or-write bank and the cache.

30. The method of claim 26, wherein reading the tag includes reading the tag before reading the word from the read-or-write bank.

31. The method of claim 26, wherein reading the tag includes reading the tag before reading the word from the cache.

32. The method of claim 26, wherein reading the tag includes reading the tag before reading the word from the reader-write bank and before reading the word from the cache.

33. The method of claim 26, wherein effecting a read access from the memory includes effecting a read access for a cache miss, further comprising writing data read from the word of the read-or-write bank into the cache.

34. The method of claim 33, further comprising writing the word read from the cache to the read-or-write bank indicated on the tag, prior to writing data read from the word of the row of the read-or-write bank into the cache.

35. The method of claim 34, further comprising updating the cache tag to indicate which read-or-write bank'"'"'s word was written into the cache.

36. The method of claim 26, wherein effecting a read access from the memory includes effecting a read access for a cache hit, further comprising writing the word read from the cache back into the cache.

37. The method of claim 36, further comprising writing the tag back into the cache.

38. The method of claim 36, further comprising writing the word read from the cache into the read-or-write bank indicated by the tag, wherein reading the tag includes reading the tag before reading the word from the read-or write bank.

39. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

receiving an incoming address request for a write access to the memory;

reading a tag of a cache having a word for one of the at least one read-or-write banks stored therein, the tag indicating which read-or-write bank'"'"'s word is stored in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request, writing data to the cache for the write access; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request, writing data to the read-or-write bank for the write access.

40. The method of claim 39, further comprising writing the data written to the cache into the read-or-write bank in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request.

41. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

receiving an incoming address request for a write access to the memory;

reading a tag of a cache having a word for one of the at least one read-or-write banks stored therein, the tag indicating which read-or-write bank'"'"'s word is stored in the cache; and

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request, writing data to the read-or-write bank corresponding to the incoming address request for the write access and invalidating the data in the cache.

42. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

receiving an incoming address request for a write access to the memory;

reading a tag of a cache having a word for one of the at least one read-or-write banks stored therein, the tag indicating which read-or-write bank'"'"'s word is stored in the cache; and

in response to the tag indicating that the cache does not contain the word of the read-or-write bank corresponding to the incoming address request, writing data from the cache to the read-or-write bank corresponding to the cache tag.

43. The method of claim 42, further comprising writing incoming data to the cache.

44. The method of claim 43, further comprising writing incoming data to the read-or-write bank corresponding to the incoming address request.

45. The method of claim 42, further comprising writing incoming data to the read-or-write bank corresponding to the incoming address request.

46. The method of claim 42, further comprising updating the tag of the cache to indicate the address of the read-or-write bank corresponding to the incoming address request.

47. The method of claim 42, further comprising invalidating the tag of the cache.

48. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

receiving an incoming address request;

reading a word from a row of a cache corresponding to the row of the read-or-write bank at the incoming address;

reading a tag of the cache that indicates which read-or-write bank'"'"'s word is stored in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, modifying the word read from the cache and writing the modified word back to the cache; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, writing the word read from the cache to the read-or-write bank corresponding to the tag, reading a word from the row of the read-or-write bank corresponding to the incoming address, modifying the word read from the read-or-write bank corresponding to the incoming address, writing the modified word to the cache and updating the tag to indicate that the word in the cache contains the word from the read-or-write bank corresponding to the incoming address.

49. The method of claim 48, further comprising reading a word from a row of a read-or-write bank corresponding to the incoming address in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address.

50. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

using at least one pipeline register to store data, including separating a cache read from a read-or-write bank write.

51. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

using at least one pipeline register to store data, including using pipeline forwarding.

52. The method of claim 51, wherein using pipeline forwarding includes using the pipeline forwarding to tolerate arbitrary latency between the read and the write portion of a read-modify-write operation.

53. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

writing a partial word to at least one of the said at least one read-or-write bank;

wherein writing a partial word comprises;

reading a word from a read-or-write bank;

replacing a portion of the read word with the partial word; and

writing the work having the partial word back to the read-or-write bank.

54. The A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

writing a partial word to at least one of the said at least one read-or-write bank;

wherein writing the partial word includes spatially separating memory cells accessed by the partial word from other memory cells in the word.

55. A method for providing read-modify-write memory from a memory having at least one read-or-write bank, the method comprising:

using at most one access to each said at least one read-or-write bank for each read-modify-write access to the memory during a single memory access cycle; and

writing a partial word to at least one of the said at least one read-or-write bank;

wherein writing the partial word includes constructing logical memory out of a plurality of actual memories including the at least one read-or-write bank and writing a partial word to the actual memories.

56. A method for providing read-modify-write memory from a memory having at least one read-or-write bank wherein at most one access to each said at least one read-or-write bank is generated for each read-modify-write access to the memory, the method comprising:

in response to receiving a read access request for an incoming address;

reading a word from a row of a read-or-write bank corresponding to the incoming address;

reading a word from a row of a cache corresponding to the row of the read-or-write bank;

reading a tag of the cache that indicates which read-or-write bank'"'"'s word is contained in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, returning data from the cache for the read access; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, returning data from the read-or-write bank for the read access;

in response to receiving a write access request for an incoming address;

reading a tag of the cache that indicates which read-or-write bank'"'"'s word is contained in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request, writing data to the cache for the write access; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address request, writing data to the read-or-write bank for the write access; and

in response to receiving a read-modify-write access request for an incoming address;

reading a word from a row of a cache corresponding to the row of the read-or-write bank;

reading a tag of the cache that indicates which read-or-write bank'"'"'s word is contained in the cache;

in response to the tag indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, modifying the word read from the cache and writing the modified word back to the cache; and

in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address, writing the word read from the cache to the read-or-write bank corresponding to the tag, reading a word from a row of a read-or-write bank corresponding to the incoming address, modifying the word read from the read-or-write bank corresponding to the incoming address, writing the modified word to the cache and updating the tag to indicate that the word in the cache contains the word from the read-or-write bank corresponding to the incoming address.

57. The method of claim 56, wherein reading a word from a row of a read-or-write bank corresponding to the incoming address in response to the tag not indicating that the cache contains the word of the read-or-write bank corresponding to the incoming address includes reading a word from a row of a read-or-write bank simultaneously with reading a tag of the cache.