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by rbanffy
816 days ago
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> Why are we shackled with slow IO port operations that replicate hardware from the era when leaded gasoline was widely available? Some may say this is legacy, yet we still rely on it today!! Does any modern x86 wake up knowing it's a modern x86 or do they all still wake up thinking they are 8086's and progressively wake up from a series of nested nightmares until it realizes the truth that it has more registers, 64-bits and SIMD instructions? Yesterday I was looking at a server board and it had the two-digit POST display. I assume it is updated with those ancient OUT instructions and attached to the last vestiges of an 8-bit ISA PC bus running at 5v TTL levels. |
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Option ROMs still start in real mode (at least for non-UEFI). The system management (SMI) handlers are still launched in real mode but too!
When the OS gets launched, l it brings up the other CPUs in real mode (INIT/SIPI), and has to do all the same gymnastics again…
Even PCI configuration space access is still supported with IO ports and that mode still required for some aspects.
Even today, the serial port still uses IO ports and interrupts just as it did 40+ years ago…
Yep, IO based POST codes are still a thing…