Got new Sapphire RX 470 Nitro+ 4Gig card - slightest BIOS mod bricks the card

[bobben2]

I am trying to BIOS mod my brand new RX 470 card ever so slightly with Polaris bios editor (just reduced Max. Mem Freq from 2100 to 1750 in the Powerplay menu).  
After cycling power the rig wont boot.   Brick..  
I have to switch to the 2nd BIOS to boot, then switch back to flash card with original BIOS.
Driver is Crimson 16.10.3, on Win 8.1.
Has anybody else had this problem and managed to resolve it?
I had no problem doing the BIOS mods on my other RX 470 cards (which are all 8Gig variant).


EDIT:
I wonder if Polaris BIOS editor has problem with the BIOS of the 4Gig model?
I can see the memory info is f.. up in the editor - because of mem straps for both Elpida,Hyunday,Samsung mem types?
Ow well, I guess I will have to try to mod using a hex editor instead and fix the check sum manually.

[bobben2]

After a bit of back and forth I found a version of the Polaris BIOS editor that can handle BIOS files with memory timings for multiple memory types.
The version I found is version 1.4.1 - Epsylon3.
So now I can modify and flash the BIOS successfully 

[_ZET_]

Better to use hex editor and be safe, but PBE is also nice

[bobben2]

For those that have the same problem I had, namely that the *regular* version of Polaris BIOS editor cant handle mem strap entries for multiple memory types:
Here is the thread that mentions the updated version of Polaris BIOS editor with download link.

https://bitcointalk.org/index.php?topic=1679847.0

[Jinx99]

Do not use PBE, if your card have Elpida memchips.

[bobben2]

Do not use PBE, if your card have Elpida memchips.

Please read my previous post carefully

[fr4nkthetank]

if you have the 4g card, then, (or the 480), just go to the bottom of the page there are links to bios mods that are appropriate.  althoughthis doesnt help you mod them yourself...
http://www.cryptominingtalk.com/flashing-bios/