P4080: Precise Cache size including tag+status etc.

mirkoliebender — Mon, 02 Jan 2017 14:11:33 GMT

Hello,

I'm currently trying to calculate the size of the E500MC L1+L2-Caches and the P4080 CPC(L3-Cache) including all of its status, tag, parity, ecc bits and so on. So far I've come up with the following results, but I would love if you guys could run them through, because there are a lot of uncertainties marked with "NOT SURE". I got all my information from the reference manuals of the e500mc and the P4080, but some important parts are missing and I guessed them to my best knowledge.

Thank you in advance and let me know if you need more information.

Best regards,

Mirko

L1-Cache:
     Data-Cache:
          - 32 KB size
          - 8-way set associative
          - 64-byte cache blocks/cache line
          --> 64 sets of eight blocks
          - four state MESI protocol
          - lock bit
          - cast-out bit
          - 1 parity bit per byte
          - 1 parity bit per tag

          --> (32 * 1024) / 64 = 512 cache lines
          Per Cache Line:
               --> 64 byte of data = 512 bit
               --> 3 Status bit (M, V, and S)
               --> 1 lock bit
               --> 1 cast-out bit
               --> data parity: 64 bit
               --> Tag size: 36 bit (NOT SURE)
               --> Tag parity: 1 bit
               = 512 + 3 + 1 + 1 + 64 + 36 + 1 = 618 bit per cache line
          --> 512 lines * 618 = 316416 bit = 39552 Byte = 38.625 KB Cache size


     Instruction-Cache:
          - 32 KB size
          - 8-way set associative
          - 64-byte cache blocks/cache line
          - Valid/Invalid bit
          - lock bit
          - 1 parity bit per word
          - 1 parity bit per tag          

          --> (32 * 1024) / 64 = 512 cache lines
          Per Cache Line:
               --> 64 byte of data = 512 bit
               --> 1 Status bit (V)
               --> 1 lock bit
               --> data parity: 8 bit
               --> Tag size: 36 bit (NOT SURE)
               --> Tag parity: 1 bit
               = 512 + 1 + 1 + 8 + 36 + 1 = 559 bit per cache line
          --> 512 lines * 570 = 286208 bit = 35776 Byte = 34.9375 KB Cache size

L2-Cache:
     - 128 KB size
     - 8-way set associative
     - 64-byte cache blocks/cache line
     --> 256 sets of 8 blocks
     - MESI protocol
     - lock bit
     - 7-bit pseudo-LRU per set --> 7 * 256 = 1792 bits
     - 7 bit data ecc per word (NOT SURE)
     - 1 bit data parity per word (NOT SURE)
     - 7 bit tag ecc per word (NOT SURE) 
     - 1 bit tag parity per word (NOT SURE)

     --> (128 * 1024) / 64 = 2048 cache lines
     Per Cache Line:
          --> 64 byte of data = 512 bit
          --> 3 Status bit (M, V, and S)
          --> 1 lock bit
          --> data parity: 16 bit
          --> data ecc: 16 * 7 = 112 bit
          --> tag parity: 1 bit
          --> tag ecc: 7 bit
          --> tag size: 36 bit
          = 512 + 3 + 1 + 16 + 112 + 1 + 7 + 36 = 688 bit per cache line
     --> 2048 lines * 688 + 1792= 1410816 bit = 176352 Byte = 172.21875 KB Cache size

L3-Cache:
     2 x CPC
     CPC:
          - 1 MB size
          - 32-way set associative
          - 64 byte per cache block/cache line
          --> 2048 sets of 8 blocks
          - MESI protocol (NOT SURE)
          - lock bit
          - 7-bit pseudo-LRU per set --> 7 * 2048 = 14336 bits (NOT SURE)
          - 8 ecc bits per 64 bits of data
          - 7 ecc bits for each 33-bit tag (tag address)
          - 5 ecc bits for each 9-bit tag (status bits)

          --> (1 * 1024 * 1024) / 64 = 16384 cache lines
          Per Cache Line:
               --> 64 byte of data = 512 bit
               --> Tag address size: 33 bit (NOT SURE)
               --> Status size: 9 bit (NOT SURE)
               --> data ecc: 8 * 8 = 64 bit
               --> tag address ecc:  7 bit
               --> status ecc: 5 bit
               = 512 + 33 + 9 + 64 + 7 + 5 = 630 bit per cache line
          --> 16384 lines * 630 + 14336 = 10336256 bit = 1292032 Byte = 1261.75 KB CPC size
          
     --> 2 * 1261.75 = 2523.5 KB Cache size
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Re: P4080: Precise Cache size including tag+status etc.

ufedor — Tue, 03 Jan 2017 05:56:05 GMT

Requested information is confidential - please create a technical case:

https://community.freescale.com/thread/381898

topic P4080: Precise Cache size including tag+status etc. in P-Series

P4080: Precise Cache size including tag+status etc.

Re: P4080: Precise Cache size including tag+status etc.