Most systems do not have 5 minute POST times. That’s an extreme outlier.
Linux runs all over, including embedded systems where boot time is important.
Optimizing for edge cases on outliers isn’t a priority. If you need specific boot ordering, configure it that way. It doesn’t make sense for the entire Linux world to sacrifice boot speed.
Old machines probably didn't, no, but I have absolutely seen machines (Enterprise™ Servers) that took longer than that to get to the bootloader. IIRC it was mostly a combination of hardware RAID controllers and RAM... something. Testing?
Yeah, it was somewhat understandable. I also suspect the firmware was... let's say underoptimized, but I agree that the task is truly not trivial.
One thing I ran across when trying to figure this out previously - while some firmware is undoubtably dumb, a decent amount of it was that it was doing a lot more than typical PC firmware.
For instance, the slow RAM check POST I was experiencing is because it was also doing a quick single pass memory test. Consumer firmware goes ‘meh, whatever’.
Disk spin up, it was also staging out the disk power ups so that it didn’t kill the PSU - not a concern if you have 3-4 drives. But definitely a concern if you have 20.
Also, the raid controller was running basic SMART tests and the like. Which consumer stuff typically doesn’t.
Now how much any of this is worthwhile depends on the use case of course. ‘Farm of cheap PCs’ type cloud hosting environments, most these types of conditions get handled by software, and it doesn’t matter much if any single box is half broken.
If you have one big box serving a bunch of key infra, and reboot it periodically as part of ‘scheduled maintenance’ (aka old school on prem), then it does.
Look at enterprise servers.
Competing POST in under 2 minutes is not guaranteed.
Especially the 4 socket beasts with lots of DIMMs.
I don't even think my Pentium 166 took 5 minutes to POST. Did computers ever take that long to POST??