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Confused on how they figured out bytes, book example:

  1. Mar 30, 2007 #1
    The Intrinsity caches are 16 KB caches and have 256 blocks with 16 words per block.

    Thus data is 64 bytes = 512 bytes.
    The tag field is 18 bits (32 - (8 + 6)).
    Total bits = 256 x (Data + Tag + Valid)
    = 256 x (512 bits + 18 bits + 1 bit)
    = 135,936 bits


    I'm confused on how they got 64 bytes then said = 512 bytes.

    Also where did they get (32 - (8+6))?
    I think i know where they got 32, because its a 32 bit address.


    Thank you.

    I took 16E3/265 = 62.5 not 64.

    EDIT:

    Okay I got alittle farther...

    16E3/16 = 1000 which is ~ 2^10 words, and with a block size of 4 words (2^2), but still not sure how they got 64 and 512, nor the (8+6).
     
    Last edited: Mar 30, 2007
  2. jcsd
  3. Mar 30, 2007 #2
    64 bytes = 512 bits

    Isn't that just what they meant?
     
  4. Mar 30, 2007 #3
    16KB is not 16E3 but 16*1024.
    16*1024/16 is not ~ but = 2^10.
     
  5. Mar 30, 2007 #4
    Ahhh thanks guys!!

    that makes sense.... it was a typo in the book.
    okay so I understand the 512 bits.

    for the:
    The tag field is 18 bits (32 - (8 + 6)).
    Total bits = 256 x (Data + Tag + Valid)

    32 bits address, is the 8 because 8 bits in a byte? still not seeing the 6 though.

    Also is the 256 x (data + tag + valid) because they said there is 256 blocks?
     
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