---------- Forwarded message ----------
Date: Fri, 15 Feb 2002 03:15:47 -0600 (CST)
From: Yale Patt <patt@ece.utexas.edu>

A student writes:

        Hi Dr Patt,

        You talked about spatial locality for caches 
        in 360N.  During a cache miss
        we go to memory and pick up a 
        few more bytes than we need, so that when the

Perhaps a few more than a few.

        neighbouring bytes are asked for they are there. 
        My question is, how do we
        handle this situation for I-Caches? 

Same way.

        Ultimately we want to bring in enough
        instructions so we won't miss again 

Right.

        right away, but how many bytes do we
        bring in? I'm thinking it 
        must be something like 50 bytes if we're talking
        about bringing in the next 10 instructions with 
        an avg of say 5 bytes per instruction.

        <<name withheld to protect the guilty>>

Generally, 32Bytes or 64Bytes, but it could be more.  Also, many 
implementations have a prefetch mechanism that on a cache miss prefetches
two blocks so you get twice that.

Yale Patt