I've been using an AMD K6 class CPU with 256 M RAM with great success as my firewall since OpenBSD 3.0. It started out as a Windows 98 machine and I was planning to give it away due to it becoming obsolete when Windows 2000 came out. But thanks to OBSD, it has become the guardian of my network and it amazes me still for the uptime. The only issue it had throughout the years was a faulty nic card which was recently replaced. The power supply and everything else is original. The secret for longevity is the adequate cooling in the case. My Soyo board places the CPU at the bottom of the case and I run two fans front and back through it. Unbelievable!
Code:
OpenBSD 4.3 (GENERIC) #698: Wed Mar 12 11:07:05 MDT 2008
deraadt@i386.openbsd.org:/usr/src/sys/arch/i386/compile/GENERIC
cpu0: AMD-K6(tm) 3D+ Processor ("AuthenticAMD" 586-class) 401 MHz
cpu0: FPU,V86,DE,PSE,TSC,MSR,MCE,CX8,PGE,MMX
real mem = 268005376 (255MB)
avail mem = 251092992 (239MB)
mainbus0 at root
bios0 at mainbus0: AT/286+ BIOS, date 05/16/00, BIOS32 rev. 0 @ 0xfb210, SMBIOS rev. 2.2 @ 0xf0800 (33 entries)
bios0: vendor Award Software International, Inc. version "4.51 PG" date 05/16/2000
bios0: VIA Technologies, Inc. VT82C597
apm0 at bios0: Power Management spec V1.2 (slowidle)
apm0: AC on, battery charge unknown
acpi at bios0 function 0x0 not configured
pcibios0 at bios0: rev 2.1 @ 0xf0000/0xb698
pcibios0: PCI IRQ Routing Table rev 1.0 @ 0xfdcd0/112 (5 entries)
pcibios0: PCI Exclusive IRQs: 5 10 11 12
pcibios0: PCI Interrupt Router at 000:07:0 ("VIA VT82C586 ISA" rev 0x00)
pcibios0: PCI bus #1 is the last bus
bios0: ROM list: 0xc0000/0x8000 0xc8000/0x4000!
cpu0 at mainbus0
pci0 at mainbus0 bus 0: configuration mode 1 (no bios)
pchb0 at pci0 dev 0 function 0 "VIA VT82C597 PCI" rev 0x04
agp0 at pchb0: v2, aperture at 0xd0000000, size 0x10000000
ppb0 at pci0 dev 1 function 0 "VIA VT82C598 AGP" rev 0x00
pci1 at ppb0 bus 1
vga1 at pci1 dev 0 function 0 "3DFX Interactive Voodoo3" rev 0x01
wsdisplay0 at vga1 mux 1: console (80x25, vt100 emulation)
wsdisplay0: screen 1-5 added (80x25, vt100 emulation)
pcib0 at pci0 dev 7 function 0 "VIA VT82C586 ISA" rev 0x47
pciide0 at pci0 dev 7 function 1 "VIA VT82C571 IDE" rev 0x06: ATA33, channel 0 configured to compatibility, channel 1 configured to compatibility
wd0 at pciide0 channel 0 drive 0: <WDC AC516800>
wd0: 16-sector PIO, LBA, 16124MB, 33022080 sectors
wd1 at pciide0 channel 0 drive 1: <ST34342A>
wd1: 16-sector PIO, LBA, 4103MB, 8404830 sectors
wd0(pciide0:0:0): using PIO mode 4, Ultra-DMA mode 2
wd1(pciide0:0:1): using PIO mode 4, Ultra-DMA mode 2
wd2 at pciide0 channel 1 drive 0: <IBM-DTTA-350840>
wd2: 16-sector PIO, LBA, 8063MB, 16514064 sectors
atapiscsi0 at pciide0 channel 1 drive 1
scsibus0 at atapiscsi0: 2 targets
cd0 at scsibus0 targ 0 lun 0: <PHILIPS, PCRW404, 1.06> SCSI0 5/cdrom removable
wd2(pciide0:1:0): using PIO mode 4, Ultra-DMA mode 2
cd0(pciide0:1:1): using PIO mode 4, DMA mode 2
uhci0 at pci0 dev 7 function 2 "VIA VT83C572 USB" rev 0x02: irq 10
"VIA VT82C586 Power" rev 0x10 at pci0 dev 7 function 3 not configured
xl0 at pci0 dev 8 function 0 "3Com 3c905B 100Base-TX" rev 0x30: irq 11, address 00:10:5a:6d:a9:c1
exphy0 at xl0 phy 24: 3Com internal media interface
ral0 at pci0 dev 9 function 0 "Ralink RT2661" rev 0x00: irq 12, address 00:14:a5:d9:0f:61
ral0: MAC/BBP RT2661D, RF RT2529 (MIMO XR)
rl0 at pci0 dev 10 function 0 "Realtek 8139" rev 0x10: irq 5, address 00:14:d1:15:81:d2
rlphy0 at rl0 phy 0: RTL internal PHY
isa0 at pcib0
isadma0 at isa0
pckbc0 at isa0 port 0x60/5
pckbd0 at pckbc0 (kbd slot)
pckbc0: using irq 1 for kbd slot
wskbd0 at pckbd0: console keyboard, using wsdisplay0
pcppi0 at isa0 port 0x61
midi0 at pcppi0: <PC speaker>
spkr0 at pcppi0
lpt0 at isa0 port 0x378/4 irq 7
npx0 at isa0 port 0xf0/16: reported by CPUID; using exception 16
pccom0 at isa0 port 0x3f8/8 irq 4: ns16550a, 16 byte fifo
pccom1 at isa0 port 0x2f8/8 irq 3: ns16550a, 16 byte fifo
fdc0 at isa0 port 0x3f0/6 irq 6 drq 2
fd0 at fdc0 drive 0: 1.44MB 80 cyl, 2 head, 18 sec
usb0 at uhci0: USB revision 1.0
uhub0 at usb0 "VIA UHCI root hub" rev 1.00/1.00 addr 1
biomask e745 netmask ff65 ttymask ffe7
mtrr: K6-family MTRR support (2 registers)
softraid0 at root
root on wd0a swap on wd0b dump on wd0b