What is the B2 bios error code and is it bottlenecking my RX 5700 XT

[Paul_DeBryon]

My son and I have been running a pair of Z420 machines for about six months now and we absolutely love them. They are both V2 machines running e5-1650V2 with 32GBGB 1866 Hynix factory memory, 500GB Barracuda SSD and 2TB Barracuda HDU. My son has a GTX 1660Ti fitted and I have an RX 5700 XT. When my machine boots up there's a B2 (error?) code that instantly pops up in the bottom right of the abbreviated POST screen. What does that signify? To power my RX5700 I am using a 6 to 8 pin adapter and a SATA power to 6 pin adapter since I am blessed with only one 6 pin on my 600W PSU. Both machines boot perfectly from cold to login in about 28 second. My GPU will max out on Heaven with it clocking up to about 2Mhz and the cooling fans desperately trying to cool it down. The card doesn't temp throttle because I 3D printed a duct that goes from the front of the chassis and places the front fan about 5mm from the front of the GPU.

My biggest question is running games, specifically Destiny 2. Dropping down to the tower I'm averaging about 56FPS on 1440p with the graphics setting on high. Now this is the weird bit, my CPU is ticking along at about 30% and my brand new RX5700 XT is running at about 50%. Nothing is bottlenecked as far as I can see but I can't get the FPS up to a reasonable speed. Is the motherboard a bottleneck? Is this what the B2 means at boot? My son's machine runs the same game perfectly at 1080p but mine is jittery as all heck. I know there are a load of parameters to screw around with but nothing is being maxed out and the FPS rate remains stubbornly low. Any thoughts would be gratefully received.

[Brian1965]

I would strongly recommend that you purchase a 6-pin to dual 8-pin PCI Auxiliary power adapter as shown below;

HP do make their own version of this adapter cable, but they can be difficult to source, (and possibly quite expensive). The above cable (from Amazon) uses 18AWG wire, which is rated at 8A, so has more than enough capacity for the RX5700 XT card. I definitely would not use the SATA/Molex connector for additional PCI power, as it is possible to overload the cable providing the single 12V rail. I.e. the Molex plug has only 1 yellow 12v cable, whereas the G1 connector has 3 yellow 12v cables - splitting the load across the multiple cables. The G1 connector is rated at 18A (18A x 12v = 216W). Your GPU is only 225W, and 75W of power is supplied by the PCIe slot, i.e. the G1 cable only needs to supply the additional 150W. This may very well be the cause of the BIOS error and poor GPU performance due to power starvation. 

[Paul_DeBryon]

Thank you for your response. I greatly appreciate it. I've ordered the cable off of Amazon and it will arrive here on the 26th of June so we'll see if that makes a difference. Is that what the B2 indicator on the POST screen means? Also I noticed that A2 shows briefly. I can't seem to find a table anywhere of what these error codes mean. Could they be in the 'Option Rom' and what does that do? My BIOS has it completely disabled and I'm not screwing with it. The last thing I need is a bricked BIOS.

BTW if anybody is interested this is my directed GPU cooling duct. The fan for theZ420 is cheap but the front cooling assembly is about $45 on e-Bay so I designed this to pull cool air directly from the front grill and blow it directly on the GPU. Anybody need the STL file?

Z420 3D printed GPU cooling Duct

[Brian1965]

Briefly caught a glimpse of your last post before it 'vanished'?

There appears to be more than one possible cause for the B2 BIOS error, but a quick google search would show that quite often, the error appeared after a GPU upgrade. i.e. adding a more powerful GPU card in terms of performance, and power consumption. Ironically, the  A2 BIOS error is indicating the BIOS is having trouble reading the attached drives, (which share the same power rail as the Molex connector your currently using to power the GPU).

[Brian1965]

With regards to BIOS settings, I have my BIOS set as follows;

Advanced\Slot Settings - DO NOT DISABLE THESE !!!
     Slot 1 Option ROM Download: Enable
     Slot 2 Option ROM Download: Enable
     Slot 3 Option ROM Download: Enable
     Slot 4 Option ROM Download: Enable
     Slot 5 Option ROM Download: Enable
     Slot 6 Option ROM Download: Enable

Advanced\Device Options
     Multi-Processor: Enable
     Active Processor Cores: All
     Hyper-Threading: Enable
     CECP Mode: Disable
     PCIe Performance Mode: Disable
     Num Lock State at Power-On: On
     S5 Wake on LAN: Enable
     Internal Speaker: Disable
     NIC Option ROM Download: Disable - THIS CAN BE SAFELY DISABLED
     NIC1 Option ROM Download: Disable - THIS CAN BE SAFELY DISABLED
     VGA Configuration: *Slot 2 Nvidia, Slot 5 Nvidia
     PXE Option ROMS: EFI - DON'T CHANGE YOUR CURRENT SETTING !!!
     Mass Storage Option ROMS: EFI - DON'T CHANGE YOUR CURRENT SETTING !!!
     Video Option ROMS: Legacy - DON'T CHANGE YOUR CURRENT SETTING !!!
     Display Out Of Orom Space Error: Disable - THIS CAN BE SAFELY DISABLED
     Thunderbolt: Unique ID

[Paul_DeBryon]

Thank you so much for all of your inputs and suggestions.

So as per recommendation I replaced the SATA power to 8 pin adapter for the RX 5700 XT with the 6 pin to dual 8 pin from Amazon (https://www.amazon.com/gp/product/B07C35YR6V.

After several boots I still get the B2 error code in the bottom right of the screen. Sometimes I see a flash of a 92 code and an A2 code but it always reverts back to B2 and then it goes into W10 load.

The Z420 has operated flawlessly and I've never crashed out to a black screen or a BSOD.

Here are some of my BIOS settings. Copyright shows it's from 2019.

This is an Image from System Information.

There appears to be a few differences between a Z620 and a Z420 BIOS. Here's my current BIOS settings

OS Power Management

Runtime Power Management Enabled
Turbo Mode Enabled
Idle Power Savings Extended
PCIe Performance Mode Disabled
Unique Sleep State Blink Rate Disabled

Power-On Options

Post Messages Disabled
Press Esc Key for Startup Menu Enabled
Option ROM Prompt Disabled
Mini Option Rom Display Disabled
After Power Loss Off
Post Delay None
Bypass F1 Prompt on Conf Changes Disabled
Remote Wakeup Boot Source Local Hard Drive
Factory Recovery Boot Support Enabled

BIOS Power On

All disabled

Bus Options

Numa Enabled
MMIO Assignment Mode Enabled
PCI SERR# Generation Enabled
PCI VGA Palette Snooping Disabled
PCI Latency Timer 128 PCI Bus Clocks
Legacy ACPI CPU Tables Disabled

Management Operations

AMT Enabled
Unconfigure AMT/ME Disabled
Hide Unconfigure ME Confirmation Prompt Disabled
Watchdog Timer 5
BIOS Watchdo Timer 5

Device Options

Num Lock State at Power On ON
S5 Wake on LAN Enabled
Internal Speaker Enabled
NIC AMT Option ROM Download Disabled
PXE Option Roms Legacy
Mass Storage Option ROMS Legacy
Video Option ROMS Legacy
Multi-Processor Enabled
Active Processor Cores All
Hyper-Threading Enabled
CECP Mode Disabled

Is there something I'm missing Is there an option in my BIOS that is incorrectly set?  Do I need to replace the PSU? I'm loathed to do it since from what I've read this PSU should be up to the job and it's part of this workstation.

Brian1965, your PXE and Mass storage options are set to EFI and mine are set to Legacy and you've included a big bold DON'T CHANGE YOUR CURRENT SETTINGS!!! And I would never dream of going against any instruction that includes three exclamation points 🙂 although I do know where the BIOS reset button is located.

A few extraneous bits of information. In slot one is a two port SATA3 interface card that's connected to a disk caddy that I use to image my 500GB SSD on a weekly basis. In slot 6 (the PCI slot) I have an old(ish) 4 port USB extention card for my music controllers (I write music as a hobby). I'm not sure if this is pertinent but I thought I'd add it for completeness.

BTW What are you using to overclock your CPU? Is it XTU?

Once again any insight into this issue would be gratefully received.

[Brian1965]

Sorry to hear you're still having the BIOS errors, but I am happy to hear you are no longer powering the GPU card from the SATA/Molex power rail. Especially since I didn't realize it was the XT version, (225W card as opposed to the RX5700 180W card). I have also had a look at the HP Z420 quickspecs and see that the Z420 supports the Quadro K6000 card, which is also a 225W card, so powering the card correctly can now be eliminated as a possible cause, (and fire hazard).

One thing to consider, (before pulling your system apart, or consider more drastic action, e.g. a clean OS install), is the fact that your Z420 appears to be booting into Windows okay, and these debug codes could be simply BIOS POST status codes, i.e. not error codes? Most of the individuals on other forums reporting these issues, are because their motherboards are freezing during the BIOS POST stage, which is clearly not the case here?

With regards to the BIOS codes;

https://www.evga.com/support/faq/FAQdetails.aspx?faqid=59363 

https://forum-en.msi.com/index.php?topic=263610.0 

To quickly summarize the BIOS codes you're seeing, (and some suggestions to try);

92 - PCI Bus initialization is started

Try removing the other PCI cards, and re-seat the GPU card, and see if the error is still present during POST? If not, add one PCI card at a time to try and identify the culprit? Do you have any other GPU card you could test? Do you have the latest RX5700 XT driver installed? (Released 10th Jun 2020). https://www.amd.com/en/support/graphics/amd-radeon-5700-series/amd-radeon-rx-5700-series/amd-radeon-... 

A2 - IDE Detect

I would check your current boot order, making sure it is set to the OS drive first, not a USB or CD/DVD drive. Check all the drive cabling - both ends. If you have various USB devices plugged in, this will increase the time to complete this stage of the BIOS POST process.

B2 - Legacy Option ROM Initialization

There are many components in a computer that contain their own BIOS (ROM) codes, (this enables them to communicate with the motherboards BIOS and CPU), such as GPU's, I/O or RAID cards, CPU + DIMMS (Microcode), DVD drives, etc., etc. Basically, almost everything. I would try stripping the computer back to the basics, leaving just the CPU, RAM, GPU and OS drive installed. Try removing the RAM modules and give the contacts a quick clean before re-seating. Also, don't forget to check all the cable connections to the motherboards are secure. Again, is this really an error code, or status code?

I can't see any issue with your BIOS settings. The reason my PXE and Mass storage options are set to EFI is due to the method of installing Windows. In very brief terms, a UEFI (EFI) installatation of Windows can significantly improve system performance, especially for newer hardware, e.g. newer GPU's, PCIe M.2 SSD's, etc. It might be easier if you have a look at this post; https://phoenixts.com/blog/uefi-vs-legacy-bios/

You can't simply switch your current legacy Windows installation to UEFI, you would need to perform a clean install of WIndows. In one of the posts I read, (with the same GPU - but different motherboard), reported that a clean UEFI installation of W10 sorted his B2 error, (freeze at POST with legacy W10 install)?

Re-overclocking, yes I'm using XTU with custom liquid cooling on my 1680 v2 CPU and GTX 1080 ti card. Just search the forum for more information. Myself and several other forum members have written detailed posts on our overclocking and modding endeavours.

You might want to bookmark;

https://support.hp.com/gb-en/product/hp-z420-workstation/5225033

[Brian1965]

I have just checked my own system during the POST screen and noticed that the codes B4, 99 and A2 appear briefly in the bottom right hand carner of the screen. If this is what you are seeing then these ARE in fact just debug status codes, and not BIOS errors.

B4 - USB hot plug

99 - Super IO Initialization

A2 - IDE Detect