I have a Via KT266A motherboard with 2 integrated UHCI USB HCD's. On an SMP kernel or with IO-APIC on UP enabled, they fail in the following way: usb_control/bulk_msg: timeout usb.c: USB device not accepting new address=2 (error=-110) hub.c: new USB device 00:11.2-1, assigned address 3 usb_control/bulk_msg: timeout usb.c: USB device not accepting new address=3 (error=-110) hub.c: new USB device 00:11.2-2, assigned address 4 usb_control/bulk_msg: timeout usb.c: USB device not accepting new address=4 (error=-110) hub.c: new USB device 00:11.2-2, assigned address 5 usb_control/bulk_msg: timeout usb.c: USB device not accepting new address=5 (error=-110) With 'noapic', or with the IO-APIC disabled in BIOS, this works fine. This applies to 2.4.20 and 2.5.63 with the same results. The system also generates fairly regular APIC errors 01 and 02, which I posted about in a previous message, but results from other operating systems make me disinclined to believe that the hardware is broken. Some data: 00:00.0 Host bridge: VIA Technologies, Inc. VT8367 [KT266] 00:01.0 PCI bridge: VIA Technologies, Inc. VT8367 [KT266 AGP] 00:09.0 Multimedia audio controller: Creative Labs SB Live! EMU10k1 (rev 05) 00:09.1 Input device controller: Creative Labs SB Live! (rev 05) 00:0d.0 Ethernet controller: Digital Equipment Corporation DECchip 21140 [FasterNet] (rev 22) 00:0f.0 USB Controller: OPTi Inc. 82C861 (rev 10) 00:11.0 ISA bridge: VIA Technologies, Inc.: Unknown device 3147 00:11.1 IDE interface: VIA Technologies, Inc. Bus Master IDE (rev 06) 00:11.2 USB Controller: VIA Technologies, Inc. UHCI USB (rev 23) 00:11.3 USB Controller: VIA Technologies, Inc. UHCI USB (rev 23) 01:00.0 VGA compatible controller: nVidia Corporation: Unknown device 0171 (rev a3) 00:11.2 USB Controller: VIA Technologies, Inc. UHCI USB (rev 23) (prog-if 00 [UHCI]) Subsystem: Unknown device 0925:1234 Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR- FastB2B- Status: Cap+ 66Mhz- UDF- FastB2B- ParErr- DEVSEL=medium >TAbort- SERR-