What kind of bad things can happen if I disable APIC (not to be confused with ACPI)?

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http://unix.stackexchange.com – 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 Goog (HowTos)