I am unable to use the 2.4.19-pre*|rc* series of kernels if 
CONFIG_X86_UP_IOAPIC is enabled for the kernel compile. The dmesg log 
file tells me to email you about the problem, so here it is! The basic 
system components are:
motherboard: LeadTek Research Winfast 7350KDA (based on the SiS 735 chipset)
BIOS: Award Modular Bios v6.00PG
BIOS id: 02/01/2002-SiS-735-7350KDA.C-00
CPU: Athlon XP 1700+

I have attached the following files:
dmesg-IOApic  - the dmesg log file when booting a kernel with IO-APIC 
enabled
lspci-wo-apic  - the output of 'lspci -v -v' when booting a kernel w/o 
IO-APIC enabled
lspci-w-apic  - the output of 'lspci -v -v' when booting a kernel with 
IO-APIC enabled
interrupts-wo-apic  - the contents of /proc/interrupts when booting a 
kernel w/o IO-APIC enabled.
interrupts-w-apic  - the contents of /proc/interrupts when booting a 
kernel with IO-APIC enabled.
config  - the .config file used for compiling the kernel

I am also getting a strange error message displayed on the console, 
which may be related to this situation:
spurious 8259A interrupt: IRQ7.
This occurs even when I run a non IO-APIC enabled kernel.

Also note that while I am using the -ac kernel patches (because of their 
support for the SiS 5513 chipset), the same thing occurs with the plain 
-rc series.

Thanks very much. By all means let me know if I can be of any further 
assistance.

Michael Blum