Hello
It might be wrong or corrupted BIOS. First of all I would check what is in the BIOS chip (just read by a programmer and compare) or write the right BIOS image to be sure.

Kami27 wrote:

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I noticed just one thing by touching a bit everywhere the mobo when it was on that the chip made by ICS near the AGP slot (which is the ICS 9148BF-53 a frequency generator, looking at its datasheet here ) was quite hot to the "finger test" (I could let my finger about 3 seconds before burning it, I'll probably test the temp later and edit this post). I was quite intrigued by that so I looked around the chip a bit but nothing seemed to be broken, no SMDs missing (there's some space to solder a little amount of them but it's clear that's from factory and not modified) or damaged.
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Yes, PLLs are pretty hot.

If ISA slots are present (and on P5A there are ISA slots) then don't use PCI or AGP display adapter for testing - you will skip alot of potential problematic points as ISA is the most simple and dumb of them all and it just HAS TO work. If you don't have ISA card then at least use PCI display adapter. I'm with Roman555 on the suspection on broken BIOS EPROM. I've seen such issues before although in older motherboards.

No matter if the card works on other boards, just at least try another agp card. Also try cleaning the agp slot (and edge of the card). Try as suggested a pci card, also other/less ram and another psu.

The ICS chip should not bet hot, let alone burn you. Use a multi-meter on continuity buzz to check for a short on the motherboard ATX pins. Put the black lead on any ground pin and try the red on all the voltage pins (12v, 5v etc.) It shouldn't buzz on any of them.

I personally own an Asus P3B-F, which has a really hot ICS chip, however, working flawlessly. It should be normal that the ICS chip is hot.
My friend got two 486 mobo last month, both of which stuck with POST code 41, exactly the same as yours. Both he and I were really confused with this problem, after then I discovered an Asus document which said that 41 has something to do with a corrupt BIOS. He got an ISA video card and, the mobo booted with bootblock BIOS complaining BIOS checksum error. What's more confusing is that after several tries the board finally booted and worked well without any recovery operation. The BIOS chip may have errors, caused by leakage of flash chips or something else. Maybe you can get your hands with a cheap ISA card and see what will happen. Hope your mobo get back to life soon as the P5A with Aladdin V chipset is really a nice board...

Thanks a lot guys for answering to this very weird problem 😀 I'll respond separately to all of you :

@Roman555 ==> I don't currently have a programmer to check that so I'll test what the others suggested beforehand. Anyways I won't throw that board away until I find a solution don't worry :p it's so rare to find them these days...

@HanJammer ==> I don't have any ISA graphics card, just VLB unfortunately, I'll try te get one ASAP 😉 edit: No VLB card worked. I tested just because they have traces from the bios chip to the 8bit ISA and some said on the forum/other topics that it could work displaying POST but... no.

@meljor ==> I already wrote that I tried a few AGP/PCI graphics cards (also tried every PCI slot btw) but nothing new so far 😒 RAM wise also and about the PSU it's a seasonic 650W 80+ gold, nothing wrong about rails (5V, -12V...), said PSU works perfectly with similar boards such as the Aopen AX59Pro, Gigabyte GA-5AX, DFI K6BV3+/66 and others...

@AvalonH ==>I will try that ASAP and tell you, thank you for suggesting 😀

@th1r5bvn23 ==> Thank you for the information. Your post seems to confirm what the others think

Hello guys, I finally managed to get my hands on an ISA graphics card (Trident TVGA 9000i-1). I tested both two ISA slots from the board and the results are the following:

The motherboard displays weird artefacts again, but different: The first screen that normally should show the BIOS of the graphics card shows instead these artefacts, then the screen goes black (normal) in order to display the POST screen but it also shows weird artefacts, more or less the same as the previous one.
The mobo keeps stucking on stepcode 41 and at that moment the speaker keeps doing short beeps... endlessly. I didn't let the mobo running more than 30 seconds because these beeps are really annoying.

... So with all of this I guess @Roman555 and @HanJammer are correct and the BIOS is corrupted. Should I try to get another EPROM for it ? Or just externally flash the one that's already in the mobo ? Maybe something else ?

You can try and use uniflash and flash the rom on another board by hotflashing it. I've done this numerous times and used a s7 board with an intel TX chipset for it, worked like a charm.

I have btw seen a few Asus boards that started working again after a fresh bios. So yes, corrupted bios can very well be the problem.

No idea about your problem, but the weird patterns from your first post are strikingly similar to what I experienced (on a very different motherboard though). Second and third image here, more about it here.

Hello guys, sorry to reply after all this time. I put the mobo aside for a moment. It was indeed a corrupted BIOS ! I'm really glad that it wasn't that complicated of a repair 😀

First, I was a little apprehensive as I hadn't any chip programmer and I finally decided to do a hotflash. I used another S7 board (MSI MS-5169) to do that and flashed the last BIOS from Asus' website in the original P5A's chip. I first tried uniflash but it didn't work and then used aflash which was successful. Then, I put the chip back in the P5A and power it on. It directly came back to life and rocking with a superb K6-III+ 450 @550MHz ! 😁

Thank you very much to everyone for your help and suggestions 😀