>I realize what you're saying, but generally speaking most systems will
>not have more than the maximum of four physical devices attached to any
>given PCI bus....

Here's one of my systems.  In the aic7880 configuration, we have 8 aic7880s
per bus where here we use 5 aic7895s per bus.  Just wanted to show that
this isn't as uncommon as you might think.

Copyright (c) 1992-1997 FreeBSD Inc.
Copyright (c) 1982, 1986, 1989, 1991, 1993
	The Regents of the University of California. All rights reserved.
FreeBSD 3.0-CURRENT #0: Fri Oct  2 13:35:03 MDT 1998
    ken@roadwarrior.plutotech.com:/a/perforce/FreeBSD-pluto/src/sys/compile/WONDERBOY2
CPU: Pentium Pro (300.01-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0x634  Stepping=4
  Features=0x80fbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,MMX>
dedicated mem= 2097152 (2048K) from 65011712 (63488K) to 67108864 (65536K)
real memory  = 65011712 (63488K bytes)
avail memory = 61030400 (59600K bytes)
Probing for devices on PCI bus 0:
chip0: <Host to PCI bridge (vendor=8086 device=7192)> rev 0x02 on pci0.0.0
chip1: <Intel 82371AB PCI to ISA bridge> rev 0x01 on pci0.7.0
ide_pci0: <Intel PIIX4 Bus-master IDE controller> rev 0x01 on pci0.7.1
chip2: <Intel 82371AB USB host controller> rev 0x01 int d irq 255 on pci0.7.2
chip3: <Intel 82371AB power management> rev 0x01 on pci0.7.3
vga0: <VGA-compatible display device> rev 0x64 int a irq 255 on pci0.12.0
fxp0: <Intel EtherExpress Pro 10/100B Ethernet> rev 0x05 int a irq 11 on pci0.13.0
fxp0: Ethernet address 00:20:13:44:bd:56
bridge0: <DEC 21150 PCI-PCI bridge> rev 0x03 on pci0.17.0
bridge1: <DEC 21150 PCI-PCI bridge> rev 0x03 on pci0.19.0
bridge2: <DEC 21150 PCI-PCI bridge> rev 0x03 on pci0.20.0
Probing for devices on PCI bus 1:
bridge3: <DEC 21150 PCI-PCI bridge> rev 0x03 on pci1.12.0
bridge4: <DEC 21150 PCI-PCI bridge> rev 0x02 on pci1.14.0
Probing for devices on PCI bus 2:
ahc0: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci2.2.0
ahc0: Using left over BIOS settings
ahc0: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc1: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci2.2.1
ahc1: Using left over BIOS settings
ahc1: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc2: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci2.6.0
ahc2: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc2: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc3: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci2.6.1
ahc3: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc3: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc4: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 11 on pci2.9.0
ahc4: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc4: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc5: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 14 on pci2.9.1
ahc5: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc5: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc6: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci2.10.0
ahc6: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc6: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc7: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci2.10.1
ahc7: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc7: Host Adapter Bios disabled.  Using default SCSI device parameters
acv_probe: cannot match device_id 0xa
eram0: <MOAB External RAM> rev 0x00 int a irq 11 on pci2.13.0
	eram0: phys_size = 64 MB
	set 9080 threshold register to 0x800
ahc8: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci2.14.0
ahc8: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc8: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc9: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci2.14.1
ahc9: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc9: Host Adapter Bios disabled.  Using default SCSI device parameters
Probing for devices on PCI bus 3:
ahc10: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci3.0.0
ahc10: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc10: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc11: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci3.0.1
ahc11: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc11: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc12: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci3.4.0
ahc12: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc12: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc13: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci3.4.1
ahc13: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc13: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc14: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci3.8.0
ahc14: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc14: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc15: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci3.8.1
ahc15: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc15: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc16: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 11 on pci3.11.0
ahc16: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc16: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc17: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 14 on pci3.11.1
ahc17: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc17: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc18: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci3.12.0
ahc18: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc18: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc19: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci3.12.1
ahc19: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc19: Host Adapter Bios disabled.  Using default SCSI device parameters
acv_probe: cannot match device_id 0xa
eram1: <MOAB External RAM> rev 0x00 int a irq 11 on pci3.15.0
	eram1: phys_size = 64 MB
	set 9080 threshold register to 0x800
Probing for devices on PCI bus 4:
acv_probe: cannot match device_id 0x9
eram2: <MOAB External RAM & Parity Engine> rev 0x00 int a irq 11 on pci4.15.0
	eram2: phys_size = 64 MB
	set 9080 threshold register to 0x800
Probing for devices on PCI bus 5:
ahc20: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int a irq 14 on pci5.1.0
ahc20: aic7895 Single Channel A, SCSI Id=7, 16/255 SCBs
ahc20: Host Adapter Bios disabled.  Using default SCSI device parameters
ahc21: <Adaptec aic7895 Ultra SCSI adapter> rev 0x04 int b irq 15 on pci5.1.1
ahc21: aic7895 Single Channel B, SCSI Id=7, 16/255 SCBs
ahc21: Host Adapter Bios disabled.  Using default SCSI device parameters
acv_probe: cannot match device_id 0x9
eram3: <MOAB External RAM & Parity Engine> rev 0x00 int a irq 11 on pci5.12.0
	eram3: phys_size = 64 MB
	set 9080 threshold register to 0x800
Enabled SERR# and IOCHK# NMIs
Probing for devices on the ISA bus:
sc0 at 0x60-0x6f irq 1 on motherboard
sc0: VGA color <16 virtual consoles, flags=0x0>
psm0 not found at 0x60
mbintr0 at ? irq 9 on isa
wdog0 at ? maddr 0xdfff0 msize 16 on isa
iic0 at ? maddr 0xdfff0 msize 16 on isa
weather0 at ? maddr 0xdfff0 msize 16 on isa
power0 at ? maddr 0xdfff0 msize 16 on isa
	Power Supply 1: DC good
	Power Supply 2: DC bad
dled0 at ? maddr 0xdfff0 msize 16 on isa
sysstat0 at ? maddr 0xdfff0 msize 16 on isa
	wdog_reset = 0, forced_reset = 0
sercon0 at ? maddr 0xdfff0 msize 16 on isa
smpte0 at ? maddr 0xdfff0 msize 16 on isa
xilinx0 at ? maddr 0xdfff0 msize 16 on isa
nvram0 at ? maddr 0xd0000 msize 1008 on isa
nvram0: size is 8192 bytes
bpeeprom0 not found
wdc0 not found at 0x1f0
npx0 on motherboard
npx0: INT 16 interface

--
Justin