I'm dealing with some really old point-of-sale machines that run a point-of-sale flavour of SuSE 9. It turns out that its kernel is affected by an old bug that makes USB 2.0 functionality unstable （hotplugging of devices may result in "control timeout on ep0out" messages in /var/log/messages, and the hotplugged device becomes unusable). I first tried to work around it by unloading the ehci-hcd module, so that the USB 2.0 devices just fallback to USB 1.1. But now I discover that an HP laser printer connected to the POS machine prints extremely slowly in USB 1.1 mode.
Some more search on Google suggests that the alternative solution is to put the noapic option in /boot/grub/menu.lst.
But what kind of bad things can I expect to happen if I disable APIC, besides performance degradation? I hear that ACPI is closely related to APIC, but I'm not concerned about ACPI because we explicitly turn it off in GRUB anyway. In theory, would some devices simply not work when APIC is disabled?
- single CPU, single core system (some Celeron 2.5 GHz)
- kernel 2.6.5-something-something