BIOS updates and CPU compatibility

A processor that fits the socket will not necessarily start. If the chip was released after the board was made, the board's BIOS may not recognise it, and the PC will power on to a black screen. Most boards in the shops have been updated at the factory by now, but older stock and open-box boards may not have been. The fix is a BIOS update, and the easy way to do it is a flashback button, which updates the board from a USB stick with no processor fitted. Check for that feature before buying an older board for a newer chip.

Why a newer processor needs a newer BIOS

The BIOS holds the code that identifies and sets up the processor at power-on. AMD and Intel both keep a socket in use for several processor generations, and each new generation needs new code that did not exist when earlier boards were built. The socket and the chipset are compatible; the software on the board is just out of date. Until it is updated, the board cannot start the processor, which means you cannot get into the BIOS to update it. That circular problem is what the rest of this guide is about.

The combinations that need checking

The general rule behind the table: any processor launched after the board's chipset generation is a candidate. The same applies within a generation, because chips released late in a platform's life, the X3D models for example, can need a newer BIOS than the first chips of the same family did. On LGA1851, 800-series boards and Core Ultra 200S arrived together, so there is little to check today, but the rule will apply to any later processors for that socket.

On AM4, the oldest boards are a special case. B450 and X470 boards launched in 2018, two years before Ryzen 5000, and gained support for it only through later BIOS updates; support on the 300-series boards before them was added later still and depends on the individual board. On some AM4 boards the update that adds new processors also removes support for the very oldest ones to make room, so read the notes on the download page if you might ever refit an early chip.

How to check before you buy

1. Find the board's CPU support list on the maker's website. It names every supported processor and the minimum BIOS version each needs. Make sure you are looking at the right hardware revision of the board.
2. If your processor needs the board's original BIOS or one from before the board was likely made, you are safe.
3. If it needs a later version, you cannot know from a listing what the board in the box has. Some boxes carry a sticker saying the board is ready for a given processor series, which settles it, but most say nothing. Assume an update is needed and check the board has a way to do it without a working processor.

With new stock of a board still in production, the odds are good, since makers ship current BIOS versions from the factory. With end-of-line stock, marketplace sellers and Warehouse boards, which may have sat on a shelf or in someone's cupboard, assume nothing.

Updating with no processor: the flashback button

Each of the four main makers has the same feature under a different name.

The procedure is the same in outline for all of them, and the manual gives the exact details for your board:

1. On another computer, download the latest BIOS for your exact model and revision from the maker's support page and unzip it.
2. Rename the BIOS file as the manual instructs and copy it to the top level of a USB stick formatted as FAT32. A small, plain USB 2.0 stick is the most reliable choice.
3. Connect the power supply to the board: both the 24-pin and the 8-pin CPU connectors. No processor, memory or graphics card is needed.
4. Put the stick in the specific rear USB port marked for the feature. Only that port works.
5. Switch on the power supply and press the flashback button. A light flashes while the update runs, typically for several minutes.
6. When the light stops or the board powers off, the update is done. Do not interrupt it before then.

If the light flashes briefly and stops after a few seconds, the board did not find a file it liked. The usual causes are the wrong file name, the wrong port, a stick that is not FAT32, or a file for a different board revision.

Not every board has the feature. It is common on mid-range and better boards and often absent from the cheapest models. Look for the button on the rear panel in the product photos, or for the feature name in the specification. If you are buying an older-generation board precisely because it is discounted, this one feature can decide whether the bargain is usable. Our brand guides for ASUS, MSI, Gigabyte and ASRock say more about which ranges have it.

If the board has no flashback button

• Borrow or buy an older processor that the existing BIOS supports, fit it, update from within the BIOS, then swap. A used low-end chip for the socket is often cheap and can be resold.
• Ask a shop. Many independent PC shops, and some online retailers at the point of sale, will update a board for a small charge.
• Return it. If it is an Amazon purchase inside the returns window and you have no other route, sending it back and choosing a board with a flashback button is a reasonable answer.
• Choose a different board. If you have not bought yet, this is the simplest fix. A newer chipset generation that launched with or after your processor avoids the question.

Updating when the PC already works

If the board starts with your processor, update from inside the BIOS using the built-in tool: EZ Flash on ASUS, M-Flash on MSI, Q-Flash on Gigabyte, Instant Flash on ASRock. The same FAT32 stick and the same downloaded file apply, without the renaming.

It is worth doing on any board you have just bought, new or used. Updates carry more than processor support. In 2023, for example, AM5 boards received updates limiting a processor voltage after reports of damaged Ryzen 7000X3D chips, and in 2024 Intel boards received updates with revised default power settings for 13th and 14th gen processors. A board that has been in a box since before those dates does not have them.

Three cautions. Do not update during a storm or on a supply you do not trust, because a power cut mid-update can leave the board unable to start, although a flashback button will usually recover it. Expect all BIOS settings to return to defaults, so re-enable your memory profile afterwards. And if your Windows drive is encrypted with BitLocker, have the recovery key to hand before you begin, because an update can reset the firmware security module that holds the key.

The update is one step in a longer routine for any open-box board. The full sequence is in our used motherboard checklist.