In 2.4.18-17.7.xsmp, hda=noprobe causes an oops on boot:

Uniform Multi-Platform E-IDE driver Revision: 6.31
ide: Assuming 33MHz system bus speed for PIO modes; override with idebus=xx
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
ide-floppy driver 0.99.newide
Unable to handle kernel NULL pointer dereference at virtual address 000000ad
 printing eip:
c01c18fa
*pde = 00000000
Oops: 0000

CPU:    0
EIP:    0010:[<c01c18fa>]    Not tainted
EFLAGS: 00010086

EIP is at idedisk_capacity [kernel] 0xa (2.4.18-17.7.xsmp)
eax: 00000000   ebx: c03e5664   ecx: c03e5664   edx: c03e5664
esi: 00000000   edi: c03e5620   ebp: c10e3de0   esp: c106ff80
ds: 0018   es: 0018   ss: 0018
Process swapper (pid: 1, stackpage=c106f000)
Stack: c01a913e c03e5664 c01a9180 c03e5664 00000009 c03e5620 c03e5960 0008e000
       c0357bbb c03e5620 c0371954 c0343fc0 c03e1a9c c03561ff c0258080 00000030
       0000000c c0256720 c0105000 c035621f c0344778 c106e000 c03447c9 c0105078
Call Trace: [<c01a913e>] current_capacity [kernel] 0x1e (0xc106ff80))
[<c01a9180>] ide_geninit [kernel] 0x30 (0xc106ff88))
[<c0105000>] stext [kernel] 0x0 (0xc106ffc8))
[<c0105078>] init [kernel] 0x28 (0xc106ffdc))
[<c0105000>] stext [kernel] 0x0 (0xc106ffe8))
[<c01072c6>] kernel_thread [kernel] 0x26 (0xc106fff0))
[<c0105050>] init [kernel] 0x0 (0xc106fff8))


Code: f6 80 ad 00 00 00 04 74 11 31 d2 8a 91 c8 00 00 00 8b 81 e0
 <0>Kernel panic: Attempted to kill init!