Subject: Re: What resets the motherboard?
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
Date: Fri, 8 Nov 2002 18:08:47 +0100
NNTP-Posting-Date: Fri, 08 Nov 2002 18:06:20 MET
Organization: Slovenija OnLine - SiOL
I would say that mobo relies on the PWGOOD signal form PSU to do that.
After PWGOOD is generated, some RC constant deep inside chipset makes some
additional delay and releases the signal.
My bet for that behaviour (need for delayed reset on pwup) would go to
something badly designed inside PSU. Either there are glitches in PWGOOD, or
voltages rise too slowly or maybe pwgood is not steep enough...
"A E" wrote in message
> Before I start reading up on every chipset out there, what circuit is
> responsible for power up reset on a PC? In the good old days of the C64,
> there was a 556 monostable that generated a ~1 second reset pulse on
> power up or reset.
> More and more people, myself included, are having strange intermittent
> reset failures in that the PC doesn't go past the memory self test, but
> a hard reset gets it going again.
> Yes, I've seen the designs with the relay that closes the reset switch
> longer, I'm not interested in that.
> There has to be a simple explanation. I don't know about the power
> supply theory, since there isn't much in my PC, yet it still has the
> Could a simple cap be drifting and changing a RC time constant
> Anyways, I guess in the meantime I'll research chipset datasheets.