An apparatus having a cache and a circuit. The cache may store old lines having old instructions. The circuit may (i) receive a first read command, (ii) fetch-ahead a new line having new instructions into a buffer sized to hold a single line, (iii) receive a second read command, (iv) present through a port a particular new instruction in response to both (a) a cache miss of the second read command and (b) a buffer hit of the second read command and (v) overwrite a particular old line with the new line in response to both (a) the cache miss of the second read command and (b) the buffer hit of the second read command such that (1) the first new line resides in all of the cache, the buffer and the memory and (2) the particular old line resides only in the memory.