Paul wrote:
> paulmd@efn.org wrote:
> > faizankhan666@hotmail.com wrote:
> >> I buyed DELL Optiplex GX270 just six months ago.It was intel P4 with
> >> 2.8GHz.When I try to ON my PC yesterday I recieved an orange light on
> >> my monitor and green on my CPU...nothing else...even not "DELL's title"
> >>
> >> .Computer man said that IC is burnt...cannot be replaced...he said all
> >> the processor is
> >> useless now...so what can I do now?
> >
> > Call Dell. These have bad capacitors, dell is replacing them.
> >
> Actual chips have been known to burn up. The ICH5/ICH5R Southbridge
> can go into latchup, and burns a spot on the top of the chip. That
> chip can also fail more silently, and just lose the use of the USB
> ports (which means the burning stopped once it disconnected USB
> power to the USB logic block or pad area).
>
> The failure mode shown here, will cause the machine to fail to POST.
> This is the more violent form of latchup, where the USB pads
> stay connected to the power long enough to fry the chip.
>
> http://www.abxzone.com/forums/intel-...light=usb+port
>
> While latchup can be caused by ESD (static discharge) into the
> USB ports, at least some of the failure scenarios don't involve
> static electricity at the time of failure. It is possible this
> is a design fault with the chip, or a problem with the motherboard
> design. But no company has claimed responsibility, and the warranty
> returns continue.
>
> Latchup is the formation of a parasitic PNPN junction in the silicon.
> The PNPN is the same device type as the SCR or silicon controlled
> rectifier. Like an SCR, if the gate voltage is high enough, the SCR
> turns on. In this case, shorting the power rails through the silicon
> die and heating it. The SCR will not stop, until power is removed,
> and the voltage drops low enough for the SCR to switch off. Since
> the user does not know this is happening, there is no opportunity
> for the power to be switched off, and the device heats until something
> else happens, like a burnout of the power connections.
>
> Paul

I'm hoping it has bad capacitors, which you can blame for causing
damage to whatever chip may have failed.