Description of Problem:

I received my RX 470 last week and after some normal tweaking, I downloaded the Polaris Bios Editor, dumped my current card’s bios using GPU-Z and copied the card's 1500 Mhz memory timings into the 1750 and 2000 Mhz speed slots. I flashed the new bios in an elevated CMD with command "ATIWinFlash -f -p 0 MOD.ROM". The flash and the new timings work great, are stable and there is definitely a sizable performance increase in both games and mining when the memory is running at 2000 Mhz with the tighter timings.

Unfortunately, there are some side effects. My motherboard long beeps 3 times during boot-up, and the Debug led for a VGA problem is lighting. Furthermore, there is no image coming from the video card until the Windows log-on screen, meaning I can't go into my motherboard's BIOS and change settings.

Troubleshooting:

Thankfully, flashing my original backed up GPU BIOS, the problem goes away.

One possible solution I found was making sure the checksum of the modded GPU bios was the same as the original one. By changing the fan’s RPM Max in the bios from 2400 to 2500 I was able to get the checksums the same, but it did not fix my issue.

Note: when dumping the newly flashed bios again using GPU-Z, I compared the two checksums in HeX editor using Checksum-32bit and they were different, maybe this is a clue to what’s happening here?

I greatly appreciate any help!!

Fixed it! By accident because I have no idea why this worked:

Went into HEX Editor, changed the timings on the original bios exactly like the modded bios. After doing this, the only difference between the MOD.ROM and the HEXMOD.ROM was one value in the beginning. This value corresponded to the checksum value being displayed in Polaris Bios Editor when opening up each of these roms. The HEXMOD.ROM got an invalid checksum error when opening it in Polaris Bios Editor.

I left the 'error' and because I had read somewhere to not care about it, flashed the 'invalid' HEXMOD.ROM into my GPU. ATIWinFlash gave me confirmation of the flash but on the confirmation screen the vendor ID and other crucial information was empty or error.

I did not trust it and, without restarting, immediately flashed back my original MOD.ROM, the one with the valid checksum.

I rebooted my computer for good measure and suddenly realized: no beeps! I can get in the bios AND have the tighter memory timings for mining and gaming. No idea why that worked, I guess GPU ROMS are kind of finicky...

Anyway, thanks for anyone reading my post, hope this helps someone.