Keep Bricking my Dell T7820 [Modding Rebar]

[pk223]

I am not sure exactly what is going on, I have tried this over weeks multiple times, and bricked a whole motherboard already; BIOS chip got fried on that one.

I got a replacement motherboard, and still trying to patch ReBar into my system (I really need to use my A770 GPU to its fullest for some projects) but I keep soft bricking it (Can recover with a USB and rcv file).

Here is my process:

• Unlock FD by jumping service pins
• Dump BIOS region
• Modify RebarDXE.ffs into BIOS dump using UEFITool (Old Engine; An error about non-uefi data in volume's free space)
• Patch using UEFITools (apparently my BIOS doesn’t need patches according to the tool)
• Using FPTW64 to flash BIOS region
• Reboot after successful flash

Unfortunately after the reboot the system bricks and won’t POST. I am attaching my settings below.

BIOS Version: 2.42.0
Intel ME FW Version: 11.22.96.2588
Intel CSME Tools Version: 11.8

I am suspecting it might have something to do with BootGuard? Is there a way to bypass this?
It could also have something to do with the "non-uefi data found in volumes free space"

Attaching a screenshot of a “successful” flash below. I would be so extremely grateful to anyone who can help me out with this/point me in the right direction. It has been a month since I have been trying to figure this out, and I have already bricked a motherboard and BIOS chip (not recoverable with CH341a as there was a short somewhere)

I can also upload my BIOS & patched .bin files for anyone to go over

 

[eidairaman1]

Build a rig.

 

[pk223]

Build a rig.

That wouldn't be any fun. I do have a "normal" rig. I like my system, would not have bought a replacement board otherwise.

 

[silentbogo]

Can you attach your old BIOS and whatever's on the output after all manipulations? I'll have a look at it.

 

[Bill_Bright]

And bricking motherboards is fun?

Dell and other factory computer builders are notorious for making proprietary modifications to both hardware and firmware. They do this for several reasons, including to cut costs and increase profits for them. This includes greater profits at the time of sale, but also with after sells support as it often forces their customers into very limited support and parts upgrade channels provided only by the computer maker. Apple is infamous this too.

Another reason is to keep people from dinking their systems to death.

So yeah, if you build your own, you can get a motherboard that complies with industry standards and thus allows user modifications that don't brick the system.

As a tinkerer myself, I do see the challenge. And for sure, taking risks (gambles) when potentially, substantial gains that might be won can be fun. But there are practical limitations too. The odds need to be in my favor - or at least even. Modifying parts that have had proprietary changes to them at the factory rarely pays off in terms of success, or in beneficial gains. And certainly voids any warranties.

Throwing money down the drain is not fun - at least not for me.

(not recoverable with CH341a as there was a short somewhere)

I doubt that. A "short" implies the path for current flow was physically re-routed causing a voltage from one circuit to be applied to a different, lower resistance circuit (typically ground). In a DC circuit, Ohm's Law dictates if the resistance goes down while the voltage remains the same, current MUST go up. And an unwanted increase in current often results in excessive heat, and potential fire.

More likely, dinking with the firmware resulted in a change to the firmware programming that blocked further changing.

 

[pk223]

And bricking motherboards is fun?

Dell and other factory computer builders are notorious for making proprietary modifications to both hardware and firmware. They do this for several reasons, including to cut costs and increase profits for them. This includes greater profits at the time of sale, but also with after sells support as it often forces their customers into very limited support and parts upgrade channels provided only by the computer maker. Apple is infamous this too.

Another reason is to keep people from dinking their systems to death.

So yeah, if you build your own, you can get a motherboard that complies with industry standards and thus allows user modifications that don't brick the system.

As a tinkerer myself, I do see the challenge. And for sure, taking risks (gambles) when potentially, substantial gains that might be won can be fun. But there are practical limitations too. The odds need to be in my favor - or at least even. Modifying parts that have had proprietary changes to them at the factory rarely pays off in terms of success, or in beneficial gains. And certainly voids any warranties.

Throwing money down the drain is not fun - at least not for me.


I doubt that. A "short" implies the path for current flow was physically re-routed causing a voltage from one circuit to be applied to a different, lower resistance circuit (typically ground). In a DC circuit, Ohm's Law dictates if the resistance goes down while the voltage remains the same, current MUST go up. And an unwanted increase in current often results in excessive heat, and potential fire.

More likely, dinking with the firmware resulted in a change to the firmware programming that blocked further changing.

I appreciate your response, and you make fair points. I guess for me I really need a rebarred A770 (ARC GPU's really struggle without ReBar) since the use case for this project is CPU-heavy first, and then GPU intensive as well. My other machines cannot keep up with the Dual Xeons & 128GB RAM. Regarding warranty, this system was a used shell I bought with warranty on it so it wasn't that big of a deal.

The info about the short is much appreciated, someone pointed me in that direction since I could not get a read on the chip without desoldering at least half of it. I did dig further into it and looks like BootGuard is preventing the system from booting due to a hash mismatch, there probably are ways to bypass this.

I didn't totally brick the other motherboard, I am planning to replace the BIOS chip sometime in the future, and got a replacement motherboard for pretty cheap since my system was still in warranty (albeit I bricked it). The only reason I am doing this is because I know of a couple people who have managed to do this, but some unreachable. Regardless, it is very fun and I am learning a lot. I have learned a lot making mistakes, and that is what brings the fun in tinkering for me. Anyone can really build a rig. Also, Apple computers/devices have been some of the most difficult, and rewarding "tinkering" experiences in the past for me, but I wouldn't daily drive them.

 

[pk223]

Can you attach your old BIOS and whatever's on the output after all manipulations? I'll have a look at it.

Thank you for taking a look! Attaching the original & modded BIOS files. Also attaching some screenshots from the UEFITool NE, & others which show some interesting information; BootGuard keys & something about AMI preventing boot due to hash mismatch - suspecting this is the hiccup.

 

[silentbogo]

Yep, you are trying to add the module into one of protected section, which breaks the BootGuard verification.
Not sure if it's even possible to do with desoldered chip and programmer, cause you still need to disable boot guard(which is only doable on much older ME versions).
Basically it's a dead-end and you have 3 options:
1) Sell A770 and replace it with NV/AMD equivalent
2) Sell T7820 and build a rig
3) Use it as-is
First and third are probably the most realistic.

 

[Bill_Bright]

Anyone can really build a rig.

This is so true. If users know the difference between a left-handed #2 Philips screwdriver and a right-handed #2 Philips screwdriver , and know how to use it, they can assemble a computer.

I wish more people understood this but sadly, too many are intimidated by the thought out of fear they might mess it up. If more users built their own, then perhaps the self-build/upgrade industry would thrive again (instead of its declining trend) with even more options for us consumers.

I note another HUGE advantage to building our own is we don't have to put up with all the crapware and extra junk and features factory builders preinstall and foist on us.

Oh well. That's for a different discussion.

I have learned a lot making mistakes, and that is what brings the fun in tinkering for me.

I agree totally. But when such mistakes become costly, that takes the fun out of it for me. I would much rather learn from other's mistakes in those situations. That's where forums like TPU come in - at least when those who made the mistakes are willing to share their experiences before I do the same.

I could not get a read on the chip without desoldering at least half of it.

I am planning to replace the BIOS chip

Been there, done that. But just keep in mind that many ICs have been destroyed by heat from improper desoldering and soldering techniques. And many more destroyed by ESD.

Anyway, it sounds like you have thought this through so that is good.

Good luck.