At 02:53 PM 9/11/2010, john s wolter wrote: >Christian, > >I must be ignorant of this need to idle a program to prevent >overheating. First thinking of the 8088/86, 80286, 80386, 80486 >system boards of the 1980's and early 1990's. I can't remember >overheating caused by looping programs. I wrote BIOS calling >assembly language routines that would poll the keyboard awaiting >input. I did not observe such overheating. > >My work after that time frame depended on the use of large shared >libraries that may have masked such issues. I've not worked at the >hardware level in the Pentium series CPU. What if anything has >changed since that time? > >What mechanism of system board design would cause such behavior? I >want to know the how of how can a system board overheat and need a >software intervention. Can you offer any online links that discuss >design issues related to this overheating.
It's more of a "reversed logic" thing... In DOS (and some other OS), looping/waiting for a keystroke will just keep the CPU running "as usual", so dissipating the same amount of heat as if it would be "really" busy. Putting a HLT instruction at the right place will cause the x86 CPU to stop executing instructions until the next hardware interrupt (like from the keyboard), which has the side effect of a drop of power consumption and hence a (temporary) reduction in heat dissipation... If the CPU is "overheating", reaching a temperature outside of its designed range, than this is a totally different issue and most likely due to some hardware issues (including dusty/clogged fans/airways) and the use of the HLT instructions rather "covers up" this issue than being a "solution". The only possibly benefit would be in battery operation, where a lot prolonged periods in HLT mode could save some battery power, but even that might be fairly relative... Ralf ------------------------------------------------------------------------------ Start uncovering the many advantages of virtual appliances and start using them to simplify application deployment and accelerate your shift to cloud computing http://p.sf.net/sfu/novell-sfdev2dev _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
