Comparisons · ASUS support FAQs (how to use USB BIOS FlashBack, and updating the BIOS including a different generation CPU), MSI's support document on refreshing the BIOS via the Flash BIOS Button, and the rear-interface lists on four ASUS and MSI product specification pages (all read 2026-09-21)

Before dropping in a newer CPU: check the specification for a button that flashes the BIOS with no CPU fitted

Keep the board, change only the processor for a newer generation, and the machine can power up without ever producing a picture. Where the cause is the motherboard's BIOS version, an update fixes it — but the usual update procedures assume the machine can boot. The new CPU will not boot it, and the old CPU has often already been sold. That is the circle. ASUS and MSI each provide a way out on some of their boards: a button that writes the BIOS from a USB flash drive with no processor fitted. This guide was written on 2026-09-21 from both vendors' support documents and product specification pages, and sets out where to check for support, what differs between the two vendors, and how four real boards came out when their specifications were read.

Published 2026-09-21 · Updated 2026-09-21 · FaultNote editorial policy

An overview of this guide’s steps and checks, not a screenshot of the app.

Who this guide is for and what to prepare

Anyone keeping an existing motherboard and buying only a newer-generation CPU
Anyone buying a motherboard now who may change the CPU later
Anyone whose machine stopped producing a picture after a CPU swap and is narrowing down the cause

What you need

Note the board's exact model name (specifications differ between models in the same series)
Check, in the vendor's CPU support list, the BIOS version from which the CPU you want is supported
Establish whether the machine can still boot at all (if it can, the ordinary update procedures apply)

1. Where the circle comes from

ASUS's FAQ carries this situation as a question in its own words: The newly purchased CPU can't power on, confirm the support list in ASUS official website indicates that need to update, how to deal with it? A newly bought CPU will not power the machine on, and the vendor's support list says the BIOS needs updating.

The answer names three methods. The first is If you have the old CPU that is listed in support list in ASUS official website and can power on, please update BIOS to the latest version and use new CPU — boot with the old, supported processor, update, then swap. That route disappears once the old CPU has been sold.

The second method is the subject of this guide: Please confirm whether your motherboard support USB BIOS FlashBack. If support, you can use USB BIOS FlashBack to update BIOS under the shutdown status. Note the order — confirm support first.

The third is If you can't update BIOS by above two methods, please contack ASUS service center for update service; the spelling is the source's. That route costs time and shipping, and whether it can be avoided is a purchase-time decision.

2. Both vendors state plainly that it is only some models

This capability is present on the board or it is not. It cannot be switched on in software: it needs a physical button and a dedicated USB port.

ASUS splits updating into two methods and attaches this to the second: Update BIOS under the Shutdown or uninstall CPU status (USB BIOS FlashBack), it's only applicable to some models. Only some models, stated outright.

MSI says the same thing in two places. It opens with you may need to refresh the motherboard BIOS using the Flash BIOS Button without a CPU and RAM, describing a write with neither processor nor memory fitted. It then states This feature is only available on models with the Flash BIOS Button. and adds Not every model supports this feature. You can check on the official website or look for markings on the motherboard.

Both also say where to look. ASUS: You can check the official website product specifications or user manual instructions. MSI names the official website or the markings on the board. So the place to check is the specification section of the product page — which is what the next section does, for four boards.

3. What reading four specification pages produced

On 2026-09-21 the product specification pages of two ASUS and two MSI boards were read, checking whether the rear-interface list names the button. The four are comparable in class and chipset generation. The results were not the same.

The two MSI boards diverge. The rear-interface list for the PRO B650M-A WIFI names Flash BIOS Button. The same list for the PRO B860M-A WIFI names Clear CMOS Button, with no Flash BIOS Button entry. The names look alike; the functions are not. Clearing CMOS returns settings to their defaults and does not rewrite the BIOS itself.

So neither "it is the newer generation" nor "it is the higher model number" predicts the answer. There is no substitute for reading the specification of the specific model.

This is what this site read on the specification pages on 2026-09-21. No hardware was examined here. As MSI notes, the markings on the board are a second way to check.

Scroll horizontally to see the full table →

3. What reading four specification pages produced
Board	What the specification names	Update with no CPU	Section read
ASUS PRIME B650M-A II	BIOS FlashBack button	Listed	Rear interface, and the EZ DIY items
ASUS TUF GAMING B850M-PLUS WIFI	BIOS FlashBack button	Listed	Rear interface, and the EZ DIY items
MSI PRO B650M-A WIFI	Flash BIOS Button	Listed	Rear interface
MSI PRO B860M-A WIFI	Clear CMOS Button only	Not listed in the specification	Rear interface

4. Where the board does have it, the two vendors differ

The purpose is the same, but the flash drive, the power connections and the button press are all different. Applying one vendor's procedure to the other's board will fail.

On the drive, ASUS states Prepare a USB flash drive with a capacity of 1GB or more. and adds the condition Requires a single sector USB flash drive in FAT16 / 32 MBR format. On the file: Extract the compressed BIOS file, which contains a BIOS file (.CAP) and a BIOS rename tool (BIOSRenamer). — the bundled tool does the naming. On power: Please shut down before using the USB BIOS FlashBack tool, but do not remove the power.

MSI states Prepare a USB flash drive and format it to FAT32 format. and names the file itself: Rename the unzipped BIOS file to "MSI.ROM" and click "Yes". Copy the renamed file to your prepared USB flash drive. Power is two connections, Connect the CPU power to the CPU_PWR1 position. and Connect the 24-pin power connector to the motherboard., and the port is specified: Insert the USB flash drive containing the MSI.ROM file into the USB port labeled "BIOS" on the rear I/O panel.

The press differs too. ASUS requires a hold and a count: Press the BIOS FlashBack button for three seconds until the FlashBack LED blinks three times, indicating that the BIOS FlashBack function is enabled. MSI describes a press, an indicator that flashes, and completion when the light goes off.

On duration, ASUS states The BIOS file size will affect the update time. It can be completed in 8 minutes. Taking longer than a couple of minutes is therefore not a reason to cut the power.

Scroll horizontally to see the full table →

4. Where the board does have it, the two vendors differ
Item	ASUS (USB BIOS FlashBack)	MSI (Flash BIOS Button)
Flash drive capacity	1GB or more	Not stated
Format	FAT16 / 32, MBR, single partition	FAT32
File name	Set automatically by the bundled BIOSRenamer (a .CAP file)	Renamed by hand to MSI.ROM
Power	Shut down first, but do not remove the power	Connect CPU_PWR1 and the 24-pin connector
CPU and memory	Possible with the CPU removed (the source's wording is uninstall CPU status)	Stated as possible without a CPU and RAM
Button	Hold three seconds, LED blinks three times	Press; the indicator flashes, and completion is the light going off
Which port	The FlashBack port (see the model's manual)	The rear port labelled BIOS

5. Conditions attached to updating at all

Having the button does not remove the ordinary cautions. ASUS states them: Updating BIOS may have the risk of not booting up. Please back up your data first before updating the BIOS.

On what not to do while it runs, ASUS states Please do not remove the USB flash drive, unplug the power supply, turn on the power or press the CLR_CMOS button during the execution. MSI puts it in terms of the part at risk: Do not power off or shut down during the BIOS refresh process, as this may cause damage to the BIOS chip.

On skipping versions, ASUS states Without any special Reason, no need to update each version, just update to the latest version. — no need to climb one release at a time. The same answer carries a qualifier, though: Before updating BIOS into the latest one, there is a special Version BIOS that must be updated into on some Models. Some models need a particular intermediate version first, which is why the model's own download page is worth reading before flashing the newest file.

ASUS also addresses Intel 800 series boards, answering whether the ME firmware still needs updating after a FlashBack: Yes, because FlashBack uses CAP files to update, you need to download the ME firmware update. Pressing the button is not always the whole job; check the model's download page.

6. What to settle before buying

First, whether this board is one you may later re-CPU. The longer a socket stays in use, the more likely a newer-generation processor becomes — and that is the moment the button matters.

Second, whether to keep the old CPU. ASUS's first method assumes a supported older processor that can still boot the board. Checking for the button before selling or trading it in keeps both routes open.

Third, that a board's BIOS version cannot be read through the box. Shop stock and used boards give no way to know it in advance. On a board with the button, an old version is recoverable without help.

Fourth, the part this site cannot settle for you: confirm support on the current product page for your exact model. The four results above are what the pages said on 2026-09-21.

7. What this guide does not say

It does not say which BIOS version first supports a given CPU. Those lists are published per model and the version numbers change.

It does not give recovery steps for a failed update. Both vendors direct failures to their support channels, and no update was reproduced on hardware here.

It does not cover the equivalent features from ASRock, GIGABYTE or anyone else. Only ASUS's and MSI's documents and product pages were read, and other vendors' behaviour is not inferred from them.

It does not say a board without the button is a bad buy. If the CPU is never going to change, this condition does not enter the decision.

Limitations and requirements

Support is per model. Of the four boards read here, the rear-interface list for the MSI PRO B860M-A WIFI names Clear CMOS Button and no Flash BIOS Button. The names resemble each other; the functions do not.
ASUS and MSI differ on drive format, file name, power connection and button action alike. Do not carry one vendor's procedure across to the other's board.
The sources state that a BIOS update carries a risk of the machine not booting. Backing up beforehand and not cutting power during the write are common to both vendors.
No update was performed on hardware for this guide. Everything here comes from the vendors' documents and product pages as read on 2026-09-21.

Frequently asked questions

A newer CPU powers the machine up but produces no picture. Is that the BIOS?

It can be. ASUS's FAQ presents exactly this case — a newly bought CPU that will not power on, with the support list calling for an update. Start by checking the BIOS version from which your board's support list covers that processor.

I have already sold the old CPU. Is updating still possible?

Yes, if the board supports updating with no CPU fitted. ASUS tells you to confirm USB BIOS FlashBack support; MSI states the feature exists only on models with the Flash BIOS Button. Where neither applies, what the sources direct you to is the service centre.

Where do I check whether a board supports it?

The specification on the product page, and specifically the rear-interface list. ASUS names it BIOS FlashBack button and MSI names it Flash BIOS Button. MSI adds that the markings on the board can be checked instead.

Will a Clear CMOS button do the same job?

No. Clearing CMOS returns BIOS settings to their defaults; it does not write a newer BIOS. The MSI PRO B860M-A WIFI specification read here names Clear CMOS Button and nothing else of this kind.

Do I have to install every version up to the latest?

ASUS states that without a special reason there is no need to update each version and that going straight to the latest is enough. The same answer adds that some models need a particular version installed first, so read the model's download page before flashing the newest file.

Sources and verification date

Sources checked: 2026-09-21. These sources support the specifications, procedures or prices discussed here. Check each source for applicable conditions and current information.

Related practical guides

ASUS support FAQs (how to use USB BIOS FlashBack, and updating the BIOS including a different generation CPU), MSI's support document on refreshing the BIOS via the Flash BIOS Button, and the rear-interface lists on four ASUS and MSI product specification pages (all read 2026-09-21) troubleshooting

PC will not boot after a CPU swap: check ASUS CPU support and required BIOS

Comparisons: browse all guides →