RAM-Disk Firewall/Router

[faulkner132]

Just a thought, but I would like to built a machine which boots off a USB-FlashDrive and runs completely in memory to do the following:

Firewall
DHCP Server
NAT
Wireless AP (would plug into switch)

The machine would have an incoming 10/100 card and a 10/100/1000 local network card connecting to a gigabit switch... I am going to be running video across the network.

I was thinking of using Damn Small Linux and modifying it to suit the needs above.

I know there are wireless gigabit routers you can get which are around $125, but my main reason for doing this is:
1 - to learn
2 - can update components instead of the entire device
3 - infinite configurability

As for hardware, I would want it to be as bare as possible. I want the machine to be silent. The processor requirements will not be anything demanding (could be a Pentium 1), but the only thing I am worried about is finding an old board to support the memory requirements (512 probably) and is capable of booting off of USB. I don't want to go CD boot, because if I update the firewall/router config I have to reburn a CD.

Anybody have any experience doing this?
Also, could you think of anything else you would add?
Other thoughts?

General comments welcome!

[glc]

You can go as far back as the Intel BX slot 1 or the Via Apollo super socket 7 chipsets for 512+ SDRAM support, but I don't know about USB boot support - probably not. You are probably going to have to use a modern motherboard, but Celerons and Durons/Semprons are plenty cheap as are micro ATX integrated boards and DDR ram. The 845G/GL/GV series Intel onboard graphics can be set to use as little as 512k shared ram, I think the Via-based AMD's need 8 megs with the S3 Unichromes.