Hi there,

I have an ECS s478 board I'm trying to get running (P4VMM2 V7.3). Physically it looks good, I know this card is notorious for its bad caps so a full recap will be in order, but right now everything looks good, no bulge, no leak, super clean - even if I know good looking caps can fail without any obvious physical damage. BIOS is AMI.

Good news: it starts.
Bad news: it freezes on "Checking NVRAM..."

Using my BIOS POST diagnostic card, all LED's and power rails look good, and I'm getting these 2 last step codes:

137= display mode set, display the power on message next
238= Initialize the bus input, IPL, general devices next, if present.

And that's where it stops. Looking at the BIOS string ID, it looks like the previous owner somewhat managed to get a BIOS for the wrong board revision on this thing which had at least 9 revisions. It's the BIOS release 06/27/2002, that after some research I found was meant for the rev 1.3 of the board. Looking at both boards, they have quite some differences. Not sure if that's the boot freeze problem, but one thing is sure, I'd like to put an official BIOS for that particular board as the very first step. But next problem is, I'm having issues with that now.

The BIOS chip is a PLCC surface-mounted chip, no socket unfortunately 🙁

After some research I found info about AMI BIOS recovery procedures. It's preatty easy on paper:

- Grab the desired ROM file, rename it to AMIBOOT.ROM, put it on a freshly formatted 1.44MB floppy.
- Boot the computer while holding Ctrl+Home
- Wait for the BIOS update to finish.

Thanks to the POST card, when booting with ctrl+home I see that it's somewhat working and getting into the right routine trying to initialize the floppy.
If I have no floppy connected, I get last code :

1ED= initialize floppy drive

...and sequences of 8 short beeps looping. If I connect a floppy, it goes further - as soon as I reach first EC code, I get a single beep, and the floppy lights up and the head starts seeking. Then it goes:

1EC= <nothing documented> 
2ED= initialize floppy drive
3EE= Look for a floppy in diskette in drive A:, reading the first sector of the diskette

Then it will keep trying several EC-EE cycles, then fails to EF:

1EF= a read error occurred while reading the floppy drive in drive A

...and restarts the whole thing. Floppy LED stays on and head keeps seeking throughout. But it never gets to F0 which is "search for the AMIBOOT.ROM file in the root directory".
So...yeah, it has trouble finding the floppy. I have tried everything I could think of:

- Many known good floppy drives, both 3.5 and 5.25
- All kind of diskettes, some being NOS, formatted in DOS, in Windows, 360K, 720K, 1.44MB..
- Many known good floppy cables, single floppy, dual floppy. It looks like this low-level routine always address drive A and I tried all permutations of drives on the ribbon cables.
- By hex-editing the BIOS file I see a mention of AMIBOOT.ROM near the end, so I'm pretty sure this is the expected filename. But as it's not reaching F0, I don't think the issue is with the file itself.
- If I voluntarily mess the config (let's say set a 5.25 drive as D1 when on a single cable), I get the same 8 beeps and ED error as when I don't have a floppy drive at all. So to me it looks like the floppy initialization routine works fine, and the fact the LED ligts up and head starts seeking confirms it. It's actually detecting and reading a floppy that fails and I have no idea why.
- I have tried many other BIOS files, even the original wrong one that is currently installed, and the same behavior happens in every single case, but again I don't think the file itself is the problem.

Would anyone have any idea or insight I haven't thought about, or other tests I could run? Could it be still linked to potentially bad caps?
Otherwise at this stage, I think my next step would be to desolder the BIOS chip and ideally install a socket...

Thanks for any help or ideas!