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 PAM - Memory Page Allocation Map 
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Joined: Sat Feb 02, 2013 9:40 am
Posts: 1531
Location: Canada
Improved the PAM component today by adding parameters to set the number of words and the bits per word in the map. The PAM component manages a bitmap of memory pages in the system. Management is much faster than what could be done by software. The PAM component keeps the bitmap internal to the component so there is no need to read or cache memory. Accesses are single clock cycle. It searches a word (typically 32-bits) at a time for free pages to allocate.
The first few pages of memory may be pre-allocated to the OS. Also, the very last page of memory is pre-allocated for the system stacks. The component keeps track of the last search position and begins new searches at that position to improve performance. IF there are no free pages the PAM returns page 0 as the result.
The component has three command inputs (alloc, free, and freeall) and a page number input and output. The command inputs could be connected to instruction set decodes in a cpu core if the PAM is integrated directly into the core. The page number input is connected to an operand, and the output is connected to the result bus.

Robert Finch

Sat Aug 29, 2020 4:38 am WWW
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