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Memory size — Parallax Forums

Memory size

El PaisaEl Paisa Posts: 375
edited 2006-06-09 13:45 in Propeller 1
I apologized if·this question has been posted before.
What limits the memory size (RAM & EEPROM)· hardware or firmware?
I hope the limitation is not the hardware, the propeller has a great future to be limited by a·undoable design.
I·think that somebody mention the limitation·was the dice size.
Is this true?
Is really a shame.
·

Comments

  • pmartinpmartin Posts: 10
    edited 2006-06-09 01:39
    From what I have read in the documentation, the memory size is fixed to 32KB. Typically, processors have part of their die dedicated to local store. For example, the local store in a desktop with a P4 could be 1MB (local store is the same as cache). From what I see of other parallax processors, this 32Kb of RAM appears to be far more than the propeller's cousins; a Basic 2px has at most 16K for program.
    Also, since it is built in hardware, future processing procedures would allow propellers to be shrunk and more memory added, more cogs, etc. Think of this as the first generation of a new family of processors; the future is very bright!

    Cheers,
    pm
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-06-09 02:14
    A couple things to note is that 32K is quite a bit of RAM for program space, it can make some data intensive applications difficult but is sufficient for most code driven applications. Additionally you can implement methods to make the space seem larger than it is, Andre has successfully used a 128K EEPROM with the Propeller and used paging techniques to expand the apparent availible total memory for the Hydra gaming system.

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  • pmartinpmartin Posts: 10
    edited 2006-06-09 12:59
    Hey Paul,
    Do you have a link to any of that paging code or the hydra system? That sounds very cool. I wa wondering if there was a way to attach RAM chips to the buses on the Propeller; I'm assuming that we can't use the I/O lines, but maybe an I2C bus could attach to an MMU?

    Just a shot in the dark; I've been living in the world of Java programming for a while, so my hardware knowledge has decreased over time...
  • Paul BakerPaul Baker Posts: 6,351
    edited 2006-06-09 13:45
    I dont think Andre has posted a website for the hydra yet, but it will be happening in the very near future (last I heard he wanted pictures of the final revision board he got last week or so). What he does is just use a larger I2C EEPROM than specified. While I do not know the specifics of how he implemented it, it is typically done by reserving a portion of the propeller memory for swap space, and having the swap management routines in the non-swap portion. Then the program running on the propeller calls the appropriate function along with the address in the EEPROM for the space to be swapped in, then after it is in an indication is sent back signaling completion (or the program sits in a block-wait for the swap). This is the most basic incarnation, there means for making it much more complicated such as having multiple swap block slots, write-back policies etc.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Life is one giant teacup ride.
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