Date   : Wed, 17 Aug 2005 21:53:04 +0100
From   : Tom Seddon <tom@...>
Subject: Re: BeebEm bug?

Joe N wrote:
> Hi All,
> 
> I'm using BeebEm 1.41 for Windows. I have noticed that it is using all 
> the available processor time, running at 99% most of the time. The only 
> reason I noticed it is because my processor keeps overheating (I think I 
> need to give the heatsink a good clean as anything processor-hungry 
> makes the BIOS alarm start flipping out that the chip is getting hot - 
> but that's another story :-) ). Anyway, I don't consider that BeebEm 
> should be eating this many clock cycles. Is it a known bug does anyone 
> know?

Probably not, that's just how these things work -- it's the same with 
games, and with other emulators. Most programs can sit there doing 
nothing whilst waiting for Windows to tell them there's some input, and 
this doesn't count as CPU usage. (I believe Windows in effect switches 
the CPU off for very brief periods of time when all programs are waiting 
for input -- which is most of the time, usually -- so it genuinely does 
count as not using the CPU.)

But in the case of emulators, there isn't such a point -- even when the 
emulated computer appears to be idle, it is in fact still running 
instructions, just instructions that don't do anything apparent. So, the 
emulator has to keep running, and you get 100% CPU usage. (This is the 
same even in 'actual speed' mode; the emulator still has to run all the 
time, but spending lots of its time running a small delay loop that does 
nothing.)

--Tom

P.S. I don't have any affiliation with quietpc.co.uk, but I got from 
them a good -- and quiet! Very quiet! -- fan for my PC (pentium III), so 
they may be worth looking at if you need a new one.