A7N8X-UAYZ MB

[Kevin]

I have had problems with the computer shutting down. I have a A7N8X-UAYZ MB
with fans everywhere, 512MB RAM, a 500 watt PSU, AMD 3000+ CPU that works
best at 1300 and an 8X AGP video card with its' own fan.

I've changed the BIOS to get it up to 2800 and it may come up. When it
does, it only lasts a short time then I get a high pitched sound for about 3
seconds and it crashes. It will not start back up for five minutes and then
only at 1300. It seems like it might be a heat problem but I swear I have a
wind tunnel with all the fans and the cross-ventilation. Hugh heat-sink on
the CPU with a fan (naturally.) Using ASUS probe the CPU temp maxed at 126
F and memory was below 122F - not hot for the equipment.

Any help or suggestions appreciated,
Kevin

 

[Paul]

I have had problems with the computer shutting down. I have a A7N8X-UAYZ MB
with fans everywhere, 512MB RAM, a 500 watt PSU, AMD 3000+ CPU that works
best at 1300 and an 8X AGP video card with its' own fan.

I've changed the BIOS to get it up to 2800 and it may come up. When it
does, it only lasts a short time then I get a high pitched sound for about 3
seconds and it crashes. It will not start back up for five minutes and then
only at 1300. It seems like it might be a heat problem but I swear I have a
wind tunnel with all the fans and the cross-ventilation. Hugh heat-sink on
the CPU with a fan (naturally.) Using ASUS probe the CPU temp maxed at 126
F and memory was below 122F - not hot for the equipment.

Any help or suggestions appreciated,
Kevin

There are two AMD 3000+ rated processors. A 10.5x200=2100MHz and
a 13x166=2167MHz. Your processor is the second of these.

You are using a 100MHz clock and with the 13 multiplier,
getting 1300MHz. The proper speed would be 166MHz clock.

You don't say whether this is the retail AMD HSF that comes
with the processor, or some third party design. The AMD
heatsink has a contact area on the bottom of the heatsink
that is off-center. If you rotate the heatsink 180 degrees
and install it, the contact patch does not completely
cover the silicon die. The uncovered section of silicon
die gets really hot, and that will make the computer
unstable. You should remove the heatsink and verify it
is installed so that the contact patch is covering the
whole silicon die. A thin coating of thermal paste
will help fill any air gaps between the heatsink and
the silicon die (not so much paste, that it gushes all
over the place).

All the fans in the world won't help, if the heatsink
is not making good contact with the silicon die.

In terms of power supplies, I recommend that the power
supply have a 5V rating of at least 25 amps. The 500 watt
rating of the supply is meaningless, if the power is not
available on the output rail used by the processor. On the
A7N8X family, I believe this is the 5V supply. I have
measured heavy consumption on the 5V rail of my A7N8X-E
with 3200+ in it, and that is where my recommendation for
the 25 amp rating on +5V comes from. A little more rating
doesn't hurt. The currents on +3.3V and +12V are much less
than the requirement on +5V. (P4 boards are the opposite, and
they get their processor power from the +12V rail. In that
case 15 amps is a basic rating, with a larger rating helping
to give the PSU a longer life.)

HTH,
Paul