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    SubjectRe: Driver for tightly coupled memory
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    On Tue, 16 Sep 2008 22:27:41 PDT, Alessio Sangalli said:

    > Well I should ask the details to the hardware engineers but it's like a
    > separate channel than the one used for main memory. It is not cacheable
    > either. To the CPU, it just appears to be mapped at some location on the
    > addressable space. Accessing this TCM will not have any impact on main
    > memory access, so bursts etc won't be interrupted; other than that, TCM
    > has double the bandwidth than standard memory - but it's tiny in size,
    > something like 8 to 32kB as I mentioned earlier.

    Ah. So it's basically just super-fast memory that can be accessed without
    going through the usual memory bus. Sounds like the cycle of reincarnation
    strikes again - 30ish years ago, the DEC PDP10/20 processors implemented the
    first few locations of memory in fast (for the time) chips, and then mapped
    the general purpose registers onto it. A favorite trick would be to copy a
    small loop into locations 0-7 and then branch to it - basically executing
    from the general registers. The *real* fun started when people started doing
    self-modifying code by doing arithmetic/logical operations on registers. ;)

    Would it be more of a performance win to use the 8-32K to store speed-critical
    code rather than a FIFO? Just another idea for what to use it for, but that
    would likely require a different API...
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