Howdy. So I was testing this "https://theretroweb.com/motherboards/s/ecs-n2u400-a" motherboard yesterday, and initially everything was looking good.

It would post with both an AGP and PCI graphics cards, and it seemed to have no issues save one. I noticed that the DDR memory I had installed was showing in the boot screen as 200mhz instead of 400. Going in the bios I noticed that the available FSB frequencies were from 100 to 200 instead of 200 to 400. Anyway, I set the FSB to 200, but that caused the computer to stop posting. I removed the CMOS Battery to reset the settings and the mobo would start posting again(that was before I found out it had jumpers for that), but like before, at 100mhz FSB.
After looking around for a bit I found out that this might be due to the fact that the Heatsink is not seated properly on the CPU(Mine's an Athlon XP 2000). As I was doing a general, quick test, I didn't clip the cooler on the socked, and generally I had no issues when testing other boards with different sockets. I just had it sitting on the processor. From the bios the temps were hovering around 26c to 27c. So it was pretty cool. But I thought it was something that might not be immediately apparent, so I clipped the cooler on the socket. Now I expect people here to be aware of what short of cooler the 462 takes. You really need to be careful when trying to clip it on. I did my best and the latches were in place without much fuss.
So, now it is the moment of truth. I sort the power button pins, and now.........it doesn't post at all. It just repeats a single loooong beep.
Needless to say I was certain I obliterated the Athlon while trying to install the cooler. I am still reeling after some time ago I got careless and fried another Athlon( I mean literally. It smelled and the cpu got burned)
I tried to look up what that meant, but I found conflicting info. Some said, it's the CPU others it's the memory, and I wasn't able to find a list with the beep codes for the motherboard. I tried different CPUs(a duron 800, athlon 1900 and athlon 2500. Yes, I like my Athlons), and it still gave me the long beep. Now, it would be a bummer if the mobo's busted, but I was relieved the Athlon is probably not the issue. So now I was left with the memory. I tried changing it, but the only thing I managed was to make it beep differently, one long beep and three small ones, after installing a dead stick of ram to see what it does. Still, I get the long beep on good sticks.