Ah cause a part of POST is link training/etc, which can make some rough approximation of error rate from SERDES eye reports. Its the same problem with computers that lack ECC, without actual hardware tests (be that POST, or HW/SW error detection) your simply praying to the data corruption and crash gods that nothing goes wrong. And frighteningly a lot of things can actually be going wrong long before you will notice the data corruption or happen to have an application crash. Thankfully HW doesn't tend to just go bad as frequently as it just has errors that can be detected consistently given sufficient error detection/testing.
But even on PC's one is generally doing the same thing the mac is doing and using preprogrammed/saved machine parameters. Its only when you plug in new ram, pcie cards, etc that a full POST sequence is run on a given bus. Something the mac can't do because it doesn't have user upgradable ram/pci cards/etc. And then your average PC also has a diagnostic mode that can be started that runs a more complete system test to report back to dell/hp/etc before they send a tech or issue a RMA.
And things like memory zeroing are frequently simply not done anymore, or there is HW in the memory controller which does it in the background during initial bootup as ranges/banks are first accessed (usually for assuring ECC is set correctly).
Anyway, the point of POST is to do some rudimentary sanity checks to report errors rather than having the OS fail bootup, or the machine acts generally unreliable. Better to see degraded link/fan/etc errors at post than wonder why your machine is just running slow or being a POS like seems to be fairly common with Mac's if you watch Rossman's channel much.
But even on PC's one is generally doing the same thing the mac is doing and using preprogrammed/saved machine parameters. Its only when you plug in new ram, pcie cards, etc that a full POST sequence is run on a given bus. Something the mac can't do because it doesn't have user upgradable ram/pci cards/etc. And then your average PC also has a diagnostic mode that can be started that runs a more complete system test to report back to dell/hp/etc before they send a tech or issue a RMA.
And things like memory zeroing are frequently simply not done anymore, or there is HW in the memory controller which does it in the background during initial bootup as ranges/banks are first accessed (usually for assuring ECC is set correctly).
Anyway, the point of POST is to do some rudimentary sanity checks to report errors rather than having the OS fail bootup, or the machine acts generally unreliable. Better to see degraded link/fan/etc errors at post than wonder why your machine is just running slow or being a POS like seems to be fairly common with Mac's if you watch Rossman's channel much.