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Altera_Forum's avatar
Altera_Forum
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20 years ago

custom instructions

Is there an easy way to write custom instructions which read and write to SDRAM?

In particular, we're trying to make an compare-and-swap instruction in order to do multi-threading.

Also, though, this would be useful for matrix multiplication instructions and vector instructions as well.

Any pointers towards a simpler interface to SDRAM than directly banging on the SDRAM controller would be appreciated; in particular if there's any way to coordinate with load and store instructions (I presume that each one doesn't implement its own interface to sdram -- is there any way to reuse their interface?).

Thanks.

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    You'd have to interface with an SDRAM controller so it's not impossible, but I wouldn't want to try either. SDRAM needs a controller to talk to it due to the complexity of SDRAM in general.

    I don't understand the idea you have all that well so I can't offer an alternative. I'm sure if someone gets this one they may have something else for you.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    20 years ago

    Basically, in order to do multi-threading safely and efficiently, you need to have some instruction which can read from a location in memory, do something to it, and write the result back to the same location in memory. The functions can vary -- add, decrement, compare and swap; it's not so important as being able to have an atomic load-operate-store instruction.

    Also, one needs this for simd instructions like vector or matrix multiplications.