[SOLVED] What happens to the old motherboard BIOS version after updating it?

[Iver Hicarte]

Greetings,

I just got this air of thought about what happens to the old BIOS version of a motherboard, does it get sandwiched? Like does the new version of a BIOS lays itself on top of the old one? Or does the old BIOS version and everything about it gets deleted and gets completely replaced by everything the new BIOS version has once it gets installed? For example, let's say I have a motherboard version called "BIOS version 1", then I updated it to "BIOS version 2". Does BIOS version 1 together with its settings, content etc. get completely erased, and everything on BIOS version 2 is put on the whole firmware and software of the motherboard? Or does it just "sit "on top of the old BIOS version, kind of like an update and just improves whatever can be improved and refined on the previous BIOS version (sorry for the poor analogy, this is the only clear way I can think of to convey what I'm asking) Just thought this was an interesting topic of discussion so I decided to post it here, and hopefully some knowledgeable people here, especially motherboard enthusiasts, can shed light on this subject.

Thanks.

 

[falcon291]

The new version overwrites the older one, and you may need to adjust settings again.

 

[DRagor]

The system can't run with two different versions of BIOS at same time so it would be completely pointless to keep previous version. Well there actually is one reason to do that - safety: in case update goes wrong you could use old BIOS to recover. However to do that BIOS chip would need to have enough memory to keep both versions at same time. That actually did happen few generations on motherboards ago, but now this is replaced with BIOS flashback systems as they are simpler (for user) solution for failed updating problem.

 

[drea.drechsler]

Greetings,

I just got this air of thought about what happens to the old BIOS version of a motherboard, does it get sandwiched? Like does the new version of a BIOS lays itself on top of the old one? Or does the old BIOS version and everything about it gets deleted and gets completely replaced by everything the new BIOS version has once it gets installed? For example, let's say I have a motherboard version called "BIOS version 1", then I updated it to "BIOS version 2". Does BIOS version 1 together with its settings, content etc. get completely erased, and everything on BIOS version 2 is put on the whole firmware and software of the motherboard? Or does it just "sit "on top of the old BIOS version, kind of like an update and just improves whatever can be improved and refined on the previous BIOS version (sorry for the poor analogy, this is the only clear way I can think of to convey what I'm asking) Just thought this was an interesting topic of discussion so I decided to post it here, and hopefully some knowledgeable people here, especially motherboard enthusiasts, can shed light on this subject.

Thanks.

A few things to consider:

A new BIOS will completely replace an old BIOS...except in some circumstances. Some BIOS's are built in modules or blocks and a new BIOS may have changes only to certain blocks. The update routine will only replace the affected blocks, leaving the others unchanged. This is why you have to follow update notes when they indicate not to skip versions (as going from ver. 1 to ver. 5, update to versions 2, 3 and 4, THEN 5) in order to ensure all the changed blocks in the intermediate versions are also updated.

And also: most BIOS updates erase old settings during the update. But sometimes they don't and they may also not completely reset all CMOS memory locations to optimized default values. That's why it's usually a good idea to do a CMOS reset or Reset to Optimized Defaults (in BIOS) to ensure that happens. Otherwise, there could be random settings in locations the new BIOS uses that leads to problems. It may not matter, it's just good insurance and not hard to do.

 

[Roland Of Gilead]

A few things to consider:

A new BIOS will completely replace an old BIOS...except in some circumstances. Some BIOS's are built in modules or blocks and a new BIOS may have changes only to certain blocks. The update routine will only replace the affected blocks, leaving the others unchanged. This is why you have to follow update notes when they indicate not to skip versions (as going from ver. 1 to ver. 5, update to versions 2, 3 and 4, THEN 5) in order to ensure all the changed blocks in the intermediate versions are also updated.

And also: most BIOS updates erase old settings during the update. But sometimes they don't and they may also not completely reset all CMOS memory locations to optimized default values. That's why it's usually a good idea to do a CMOS reset or Reset to Optimized Defaults (in BIOS) to ensure that happens. Otherwise, there could be random settings in locations the new BIOS uses that leads to problems. It may not matter, it's just good insurance and not hard to do.

Just to add to @drea.drechsler excellent answer, you can also do a 'hard reset' as is outlined by @Darkbreeze in this thread: [SOLVED] - PC Constant Restarts (NO BSOD) | Tom's Hardware Forum (tomshardware.com)

 

[drea.drechsler]

The system can't run with two different versions of BIOS at same ...

And one other point to make!
SOME boards have two BIOS's...dual BIOS boards like some of Gigabyte's Ultra Durable line. What I've never understood is exactly how the "back-up" BIOS gets updated on those boards. It seems an especially relevant concern for the AM4 boards that have seen so many CPU generations supported.

A particularly evil situation: what happens if you have an Zen 3 CPU on a B350 board (that had the primary BIOS updated to support it) and it finds cause to use the backup BIOS...but it was never updated to one that supports the CPU? Is it now a brick?

 

[DRagor]

What I've never understood is exactly how the "back-up" BIOS gets updated on those boards

That's because such info is just not available. Even information on how to boot from secondary BIOS is not easy to find while logically it should be in motherboard manual of any mobo equipped with dual BIOS. Cool feature that was completely user unfriendly because of such little details.

 

[drea.drechsler]

... Cool feature that was completely user unfriendly because of such little details.

And one, it seems to me, is nearly useless even so. To me, a better feature is a "backup CMOS". That would be optimized default settings that automatically kick in after one or two failed POST's.

Some do that, but they erase the existing settings and replace them with default settings. A "backup CMOS", as I envision it, would retain the settings so you didn't have to re-enter all the changes you might be in the midst of, and therefore haven't saved to an OC profile yet.