On 01/03/2013 12:57 PM, dmccunney wrote:
> On Wed, Jan 2, 2013 at 7:57 PM, Jim Lemon<j...@bitwrit.com.au>  wrote:
>> If there was a Linux kernel in which the user could turn off everything that
>> isn't in DOS, that would be a way out.
> If you could turn off everything that *isn't* in DOS, you might have
> fun running the Linux kernel.  You run DOS in an emulator on top of
> Linux because you can't *get* DOS to run native on that hardware.
> Drivers are needed that don't exist.
> What you probably want is a flavor of Linux modified for use in an
> RTOS, where a user process can preempt the kernel itself.
Exactly. I intend to try out RTLinux at some point.

> But on modern hardware, "other time-critical programs that will carve
> out slices of CPU time" are likely a "Who cares?" issue.  Commonly
> used hardware is orders of magnitude faster than the machines DOS was
> made to run on, and there are cases like games where you might
> specifically *want* to steal CPU slices, because otherwise your game
> runs *too* fast and is unplayable. .
I have had to do this once, when writing an assembly code driver for a 
digital rotation encoder. The read cycle had to be slowed down by a 
specified number of NOPs to allow the register to load. The problem is 
that when a program is monitoring response devices such as the mouse and 
keyboard and presenting an animated display to the user, even a 
millisecond lost to some other program is a disaster. As I can often see 
the system "blink" on modern PCs running Windows and even Linux, I'm 
reasonably certain that I can't trust them to be accurately recording 
reaction times. One of my colleagues thought that she had solved the 
problem by buying an expensive test battery until I showed her the 
"uncertainty" factor that came with every response recorded.


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