Archived from groups: alt.comp.periphs.mainboard.asus (
More info?)
In article <cq0p27$2r6m$1@otis.netspace.net.au>, "Blaedmon"
<ass@beamer.com> wrote:
> BIOS? If youve the stomach for it, you could try a hotflash if youve another
> a7n8xx handy. Or badflash.com could help. You could also try the old 'remove
> everything except ram and cpu with autoexec bios on floppy' trick.
Unfortunately, the red LED is driven by a simple hardware circuit
and not by the BIOS.
There is a pin on the AGP slot. It is pin A2, and its name is TYPEDET#.
When a video card makes no connection to the pin, it is the video
card's way of saying it prefers 3.3V operation. If a video card
grounds that pin, it means the video card prefers 1.5V operation.
The 1.5V supply is suitable for operating both 4X and 8X AGP rate,
as even though signal levels on the I/O are 0.8V when running 8X,
the actual power used on the chips is still 1.5V. That is why this
pin only has to indicate two voltage preferences.
At some point several years ago, Northbridge chips started being
introduced, that could only run the AGP interface at 1.5V or less.
The Northbridge would be damaged, if it was ever put in a situation
where 3.3V was used on the AGP interface. Asus introduced the simple
transistor circuit, to monitor pin A2 TYPEDET#, to make sure that
only a "1.5V preferring" video card is being used.
One way your symptom could be caused, is if pin A2 was no longer
making contact with the video card. For example, if the video card
is not "bottoming out" in the AGP socket, that would be enough to
do it.
I would recommend the cardboard test. Remove motherboard and PSU from
the computer case, and reassemble the system on your table. Place
a piece of cardboard and a large book underneath the motherboard, so
the motherboard does not get bent when you insert components. It must
be properly supported mechanically while you work on it.
(A little less work, would be to loosen the screws holding the
motherboard, and realign the motherboard so that the AGP video cards
can get in and out of the slot easily. I have a fair amount of
trouble with alignment on my computers here, so that is worth a
shot. Also, if you are using brass standoffs from another computer,
be aware that the height of the motherboard above the motherboard
tray is critical to the video card faceplate fitting the computer
case properly. You don't want the video card "tilted" in the
AGP slot, with one end of the video card sinking deeper into
the AGP slot than the other end. Misalignment will cause the
wrong pins to mate.)
With the motherboard outside the case, it should be easier for you
to examine what is going on around pin A2. The pinout of the card
is on page 50 here:
http://web.archive.org/web/20030314013601/http://developer.intel.com/technology/agp/downloads/agp30_final_10.pdf
and the location of the pins is on page 15 of this document:
http://web.archive.org/web/20000815090340/http://www.agpforum.org/downloads/apro_r10.pdf
I believe the A7N8X Deluxe has an AGP Pro slot, so in the figure on
page 15, you'll have all the pins shown. For a non-AGP Pro slot, only
the Axx and Bxx pins exist. The "A" pins are on the backside of the
card, and A1 is on the I/O plate end of the card, while A66 is on
the end furthest from the I/O plate. When the video card grounds pin
A2, that allows the power switch to work, and turns off the red
LED.
HTH,
Paul
>
> <grantb@dahat.com> wrote in message
> news:1103346181.811196.184450@c13g2000cwb.googlegroups.com...
> > This evening I went to upgrade my A7N8X Deluxe based living room PC to
> > have an ATI 9200SE from a GeForce 3.
> >
> > After shutting down the system and swapping the cards, I found that it
> > would not power on at all. I quickly discovered that the red AGP
> > warning LED was illuminated, so I swapped back in the GF3, and applied
> > power, only to find the LED was illuminated again.
> >
> > I've tried resetting the bios, even unplugging everything from the
> > motherboard except for the CPU, it's fan and the PSU and still no
> > because the red LED is on now when ever the motherboard has power.
> >
> > Short of declaring the motherboard dead and beyond repair, would anyone
> > have any ideas?
> >
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