Radeon R9 280X 3Gb useable vs. 24Gb installed GDDR?

Discussion in 'Videocards - AMD Radeon' started by twixo, Jun 18, 2017.

  1. twixo

    twixo New Member

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    GeForce GT 640M
    Hi,

    I am checking on possible GPU upgrades for a technical application.

    I am wondering why there are 24Gb GDDR (12x SK Hynix H5GQ2H24AFA-R0C, each 2Gb) on a Radeon R9 280X with "3Gb".

    On the 6Gb version are 48Gb (12x 4Gb).

    What is all this excess memory used for?

    T.
     
  2. lexer98

    lexer98 Master Guru

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    GPU:
    GTX 1070 - WC
    R9 280x uses AFR chips each one is 256Mb
     
  3. Kaarme

    Kaarme Master Guru

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    Sapphire 390
    There's some confusion about bytes (B) and bits (b) here. Bytes are eight bits, so 24Gb is 3GB. 6GB is 48Gb. 256Mb is only 32MB, so a 3GB card would need a whole lot of such chips. However, 256MB is indeed 2Gb.

    Individual memory chip capacities are oft stated in bits, as opposed to bytes. Consumer information typically talks about bytes as that's relevant to consumers. The place where consumers most often deal with bits are Internet connection speeds. They are typically listed in bits because the numbers are thus eight times higher and look much better in ads. Even though everybody still downloads stuff sized in bytes.
     

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