XML CO527 Anonymous Questions and Answers Keyword Index

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Keyword reference for register-file

Question 7 (2014):

Submission reference: IN3417

Regarding your lecture today: For most programs, some general data memory is required (somewhere for the contents of variables to be stored). However, previously in the lecture, the slide covering the register file seemed to do this too. Have I got the wrong idea entirely, or can you sometimes use the the register file for the same thing as the SRAM?

Answer 7:

Yes, you can. However, bear in mind that the register file only holds 32x 8-bit values, so as long as your program never needs more than 32 values stored simultaneously (including temporaries during calculations) then the register-file would do just fine! The reality is that most programs need substantially more storage, e.g. the SRAM holds 1024x (or 2048x) 8-bit values [depending on the particular AVR device]. One way of looking at it is the register-file being a "cache" for stuff in SRAM, though that's a slightly naive view (the two, at the architectural level and for instruction encoding, are treated differently). There are more subtle differences perhaps, but we'll see those as we get onto programs that actually need to store stuff (e.g. a string of data received from the serial UART).

Keywords: register-file