[Info-vax] Y3K for PDP-11 Operating Systems

[Johnny Billquist]

On 2011-05-10 11.58, Bob Koehler wrote:
> In article<4dc972d1$0$73606$815e3792 at news.qwest.net>, G Cornelius<cornelius at eisner.decus.org>  writes:
>>
>> References to a 1-1 MOVTUC table are basically wasted memory
>> accesses, and, in fact, will be mostly cache misses until a
>> significant proportion of the table has been loaded.  Not to
>> mention having flushed information out of cache, resulting in
>> likely cache misses later.  Also: these are per-byte cache misses,
>> where actual data fetches should load four, eight, or even more
>> soon to be used bytes into cache whenever a miss occurs.
>
>     Caches have got large, and most likely misses would all be resolved once
>     early in program execution.

The cache warmup is an issue, since most strings aren't that long, and 
the MOVTUC will probably not hit that many locations that many times 
when implementing a strcpy(). So performance hit is probably very 
measurable.

And the table will most of the time probably not be around in the cache 
by the next time strcpy() got called. Even though caches have grown 
large, so have programs.

	Johnny