At 03:50 AM 2/17/1999 Larry Atlow wrote:
>
>                 . . . When you perform a reset,
>it causes the machine to go through its boot sequence
>just as if the power had been turned on with the
>exception of the state of the memory.  Whatever is
>in memory MAY remain there. . . .
>
>When the power is removed and left off for 10 seconds
>or more (cycling power), then any residual electical
>charges left on the motherboard, memory or peripheral
>cards are allowed to bleed off thus leaving everything
>in a known default power off state.
>
>. . . If the memory is NOT initialized to a known state
>and the software just uses the values it finds there,
>then the program's actions will be unpredictable. . . .


Just to add to Larry's fine explanation. . .

The RESET interrupts the Power Good Signal from the
power supply and the motherboard initiates a cold boot.
The signal clears the CPU registers and resets the program
counter and loads the ROM instructions for the BIOS boot
program. Then, the POST is run.

If you have the memory test enabled in CMOS, the RAM
will be written to, so all artifacts are overwritten.
HIMEM.SYS also has a thorough RAM write/read testing
procedure. However, any memory or memory cache off the
motherboard may or may not be initialized (although a
well-designed peripheral should re-initialize memory
values upon RESET).

In a perfect world, a RESET is as good as a power cycling
but just to be totally assured there are no lingering
artifacts, you must completely power down. That's the
reassuring way of resetting the system, and removes any
doubt of a "clear slate" state of the system.

Then again, there are always programs (including OSes and
microcode) that write values to disk and reload them upon
re-execution, so you might have to clear those values, too.

Regards,

John Chin

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