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G75VW VBios Help

0neWinged
Level 9

‎06-11-2016 10:04 AM - last edited on ‎03-05-2024 07:50 PM by Community Admin

Alright so I have an Asus G75vw with a GTX 660m. I bought a GTX 780m and heatsink from a G750jh. I did some chassis modifications and managed to get everything to fit. Flashed new bios with vbios of 660 and 780.
I turned off UEFI prior to flash, turned UEFI off prior to card swap. Laptop fired up, but boots to Asus boot logo screen, (where you would normally access bios) but gets stuck. I cannot access bios. Trouble shooted a few things, but still no luck. Even swapped back to the 660m and boots passed the boot screen. So I then re flashed to my stock bios, and tried swapping to 780m to see if it wouldn't show the boot screen, but it does the same thing.
So.. From what I am told it is trying to load the VBIOS onboard of the 780M PCB. Also was told It definitely is a module regarding PEG control. This should be in the unlocked "Chipset" tab, but as I've mentioned a while back, this is where things can bjork the boot block and even the recovery block if a setting you enable is deep BIOS disabled.. (no supported callback module) meaning, ICSP programmer is the only way out of it. (Don't want to brick or have to find a ICSP programmer).
Any insight would be appreciated. I also have this up at WIN RAID forum as well, but figured it can't hurt to have more eyes and brains.
In the end, I just want this thing to recognize the 780 as its card and boot. I already have modified drivers, just need a successful boot.
Anyone willing to help with this modification will be highly highly appreciated.
Thanks!
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jmhdj
Level 10

‎06-12-2016 04:41 AM

Hi. As I remember correctly G75 series has vbios inside of main system bios. Correct me if I am wrong. Did you remove completely 660m vbios from bios or just added 780m vbios on top?
Did you tried 780m with UEFI enabled?
Where did you got 780m vbios you inserted inside bios?
Is it asus 780m vbios?
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0neWinged
Level 9
In response to jmhdj

‎06-12-2016 10:24 AM

jmhdj wrote:
Hi. As I remember correctly G75 series has vbios inside of main system bios. Correct me if I am wrong. Did you remove completely 660m vbios from bios or just added 780m vbios on top?
Did you tried 780m with UEFI enabled?
Where did you got 780m vbios you inserted inside bios?
Is it asus 780m vbios?


Ah the man I've been waiting to hear from!! Lol
Yes G75 does have vbios inside of main system bios.
I have been working with Dreamonic up to this point and talking with him on his site voltground. I dumped my bios and I uploaded to him. Which has 660m and 670m vbios. He removed 670m vbios and replaced with 780m. So the newly modified bios has 660m and 780m vbios.
I did try 780m with UEFI enabled, still same result, stuck at ROG boot logo.
Dreamonic had the 780m vbios and I'm almost positive he used Asus 780m vbios.
Im worried to flash only 780M Vbios as I may get stuck trying to revert due to the fact I cant access bios or boot menu with 780M installed and probably not be able to access bios or boot menu with 660M installed

Ill inform him of this thread so he can pitch in too. Hes smarter than I am on this bios mod subject and would be able to provide better details than me. Ill have out convo points uploaded as they are PM and not a thread so I can provide a link. Ill also provide links for all bios/vbios .rom files that were used.



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jmhdj
Level 10

‎06-12-2016 10:53 AM

Dont know what to say as I havent mod anything beyond asus G73 models. You would have better chance for help from dreamonic if you could take whole bios dump. Only way to get whole dupm is to desolder bios chip and read it with soic reader.
What could be another route is to see if there are different revisions of asus 780m vbios.
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Dreamonic
Level 12

‎06-12-2016 11:05 AM

It is indeed the ASUS 780M VBIOS and no, flashing with just the 780M OROM isn't going to help at this point as the VBIOS onboard the 780M is definitely being used. My guess is it's either PEG control/BUS interface as the system BIOS callback is to the OROM for the GPUs in the G75 unlike the G750. However, with just the 780M installed with nothing else done, the display still actually works too. The fact it's preventing BIOS access leads me to believe it's certain callback modules that the G750 has for read/write (0xFF) access to the BIOS chip onboard its PCB through ASUS MXM structure as faults have been detected. I believe those correct modules are the LegacyRegion2 (G750) and PciExpressDxe (G75) modules and a couple others. It's now getting to a point where it can potentially corrupt the boot block and recovery block should it not succeed (requires HW programmer) through experimentation.

EDIT: Now I understand jmhdj, you've done the G73JH that has only the ATI GPU HW callbacks with the G73SW that has only the NVIDIA GPU callbacks. This I understand. What is strange with our modification is the MXM GPU > OROM > System BIOS in the G75 to the MXM GPU > GPU VBIOS (onboard) > System BIOS (no OROM) in the G750. Since one reads differently than the other yet the display is still being initialized... that's the part I'm trying to figure out. That means the VBIOS is correct but modules in the system BIOS are not configured for it.
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Dreamonic
Level 12

‎06-12-2016 11:12 AM

I wonder if shorting (prior to boot - temporarily) the 780M BIOS chip to bypass it would allow the read of the OROM (VBIOS inserted) instead...
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jmhdj
Level 10
In response to Dreamonic

‎06-12-2016 11:18 AM

Dreamonic wrote:
I wonder if shorting (prior to boot - temporarily) the 780M BIOS chip to bypass it would allow the read of the OROM instead...


It cant hurt at all, as long as he dont short something other 🙂
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jmhdj
Level 10

‎06-12-2016 11:16 AM

Sounds like logical and probably correct diagnosis. As for which modules inside system bios are responsible your gues is better than mine 🙂
Wish you best luck further.
Will watch over this thread and if I get any ideas will post them.
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jmhdj
Level 10

‎06-12-2016 11:21 AM

If I remember long time ago other guy tried to upgrade his G53 with asus 780m gpu and we found that asus 780m is mechanicaly different from standard mxm 3.0 gpu's.
Will check on this as I am not sure my recolection is good.
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Dreamonic
Level 12

‎06-12-2016 11:34 AM

They do have their own proprietary PCB design but the MXM connection shouldn't have changed according to this:

MXM Version 3.0 Technical Brief
MModule Concept

The MXM version 3.0 specification allows system designers the flexibility to customize the module
in a OEM shipping configuration. The MXM version 3.0 specification achieves this goal by allowing
the freedom to use OEM-specific, non-compliant, modules in an MXM version 3.0 compliant system.
Common scenarios are:

Form Factor

OEM modules are allowed to use non-standard form factors as long as the system can
accommodate MXM version 3.0 standard modules.

VBIOS ROM

OEM modules are not required to have a ROM chip as long as the system can correctly
operate using a standard MXM version 3.0 module with on-board VBIOS ROM.

Power

OEM modules can rely on additional voltages supplied by the motherboard. OEM reserved
pins are provided by the specification. All MXM version 3.0 compliant modules will not connect
these pins.

Extra Signals

OEM modules are allowed to use extra signals provided by the motherboard. OEM
reserved pins are provided by the specification. All MXM version 3.0 compliant modules will not
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