Rpi 3 - damaged processor replacement

[twizzter]

Rpi IOs are not well protected. My board was damaged - HDMI port failure and stopped working at all after while.
Decided to take a risk, go into adventure and bought new processor from our chinese friends.
I've replaced chip. No shorts on PMIC, voltages are OK, chip is cold.
Did fast check on card area - no shorts, VCC ok, i see signals on SD clk and data pins.
Managed to enter "rainbow" screen when booting from card taken from RPI4. Fresh burned image does nothing - black screen, no green led activity.
Assuming that chip was a geniune/new and i did my resolder part correctly, is there additional configuration (like ram info?) which is required to be done on BCM2837 in order to boot?

In other words - is "factory" first OTP bootloader capable of booting from SD out of the box?

[wraper]

There is virtually zero possibility of a new chip, unless it was stolen from factory. I'm surprised you managed to find where to buy it at all. If there are no faulty components on PCB, it should work right away. If voltages are OK, and CPU is known good, I would suspect bad RAM. But from my experience symptoms are more like a bad CPU or soldering issue. Measure current current consumption without a memory card inserted.

[twizzter]

Bare board consumes about 50mA on start and stays at 80mA after few seconds.
You're right, i can't be sure about chip quality. Especially from ali shady sellers.
I'll try to poke chip under hotair and i guess that's last thing i can do before trash slam dunk 

[wraper]

Bare board consumes about 50mA on start and stays at 80mA after few seconds.

That's about what should be normally.

[YetAnotherTechie]

there is otp fuse in the cpu, you need to check that they match what rpi uses. plenty of info on rpi site. i don't know how you would program it if you can't boot 

[wraper]

there is otp fuse in the cpu, you need to check that they match what rpi uses. plenty of info on rpi site. i don't know how you would program it if you can't boot 

That OTP discussed on the forums is about USB boot. It does not prevent booting from SD.