Couple of things…
asv, knowing your budget a bit better, I’d advise you to check out Core Duo instead of Pentium M. Or if power is really a concern, try the low voltage or ultra low voltage CD/PM (ULV Core Duos can get expensive fast, the Pentium Ms might be better in that regard) variants. Note: Core Duo 2s come in Socket 479 and LGA 775 options. The Socket 479 boards do Pentium M, Core Duo 1, and low voltage as well. The LGA 775s don’t.
That Kontron board was what I wanted to use in my Core Duo 2 setup for months so I could use a low voltage Core Duo 2. It probably would retail for around $300, since most of my boards won’t need the 6 SATA ports, at 4 boards with one SATA RAID card (I recommend HighPoint 2220s at $250) using the Kontron board would be slightly cheaper than the one I eventually picked and Kontron is a good company. Did they finally release the thing? For awhile I checked religously to see if I could buy it anywhere, but with no luck.
The Pentium M board you linked to is okay overall, good for the price. The lack of SATA, only DDR-333, and those odd white connectors (might need a special cable for USB or serial, though they seem to have most on the hood) are my only reservations.
As far as a 4Gb drive. If you are using a Compact Flash card with an IDE adaptor, or some kind of IDE plugin module, you can install Linux directly onto the module. If you’re using a USB thumbdrive or MMC via USB (I won’t do this), you might have to do something more complicated.
I don’t know how much space is needed for a default DSL install, but a minimal Debian install (off the stock netiso) only takes up only 160MB (Not sure if it needs more for the actually installation, I’ve never tried to go as low a 256Mb, worked fine on 1Gb). Once nice thing about Debian is that in the vast majority of cases you can just rsync -auxv / /(where the other drive is mounted), then boot up grub to configure the MBR and you’ve effectively duplicated your boot image. When I upgraded the terminal machines in my lab (they had be designed diskless) to disked 80GB SATA drives, I got one working, then just imaged all the other drives.
As far as power, 60W will be enough for a Pentium M or Core Duo (under 30W) since you’re running from flash and not adding a powerful video card, and PicoPSU is pretty good railwise. If you might use this as a desktop (add a red or green video card) or a server (add a bunch of hard drives), you might want to get the 80W since the price isn’t that different.
Note I’ve used the power simulator before. It’s nice as a rough guide, but things like a 5 1/4 CD-ROM taking 25W are plain wrong, I have DVD burners that don’t pull that much when burning. If power is a real concern and you want a CD drive on the bot, obviously use a slim CD (I think space might be a better reason). Similarly 15W for 3.5" hard drive is also not really accurate, while a correct average. Different drives and different sized drives have different pulls during use/idle and startup (biggest concern). Any new SATA drives has about 6W pull (80Gb Seagates/ WDs/ Hitachis) to 12W pull (200Gb WDs, 250Gb Maxtors, 500Gb or 750Gb Seagates). What kills you is startup. These drives can pull 25W on spinup, so if you’re making a RAID array a controller with staggered spinup is a must. However, since the processor isn’t at full load, you can sneak past boot if you only have one or two drives.
As far as distro, Debian is a good choice since you’re coming from another package distro. If you plan on having tons of programs or data you might want to check out Gentoo just because installing much beyond the base system (mainly anything with X dependencies) on Debian is watseful since they don’t really minimize package dependencies. I.e. to install something like OpenCV (vision recognition) and development libraries on your bot, you’re going to end up using the same space as a minimal KDE configuration (around 3Gb).
I do fully agree with linuxguy that you should install Debian on an extra PC (if you have one) or just do a test install on the bot not worrying about space, as it will help you learn all the administrational stuff first. Granted having used REL breifly, I think you’ll find it much easier.
As far as hardware goes, Debian Etch (testing) uses a 2.6.18 kernel and Debian has really good tools for compiling custom kernels (I know way too much about this, so feel free to ask) so if your hardware is supported at all, it will work. I’m sure you already know the things that don’t work well under Linux, but unless you chose a VIA board with its bizzare chipset hardware accelerator (again for MPEG, AES, and GUI stuff, all CLI stuff should work fine) the biggest issue you’ll encounter is picking the right WiFi card. All but the newest red and green video cards work (though performance might not be as good as it can be), and I doubt you’re using one, a printer/ scanner, or odd RAID card or bluetooth dongle (the other areas where Linux is weak with hardware support) on this project. Red Hat ships a highly patched (and thefore now requiring much more testing) kernels and lag behind. Debian’s kernel is more or less a vanilla one with a few Debian patches and some standard distro defaults applied. The real reason for the Debian patches is more to make sure the kernel works with the package management system, things go in the right place, and if you compile things oddly Debians default tools can handle it. They are not the driver extensions and experimental tools (a la GFS) that exist in the Red Hat world.
As far as your flash drive becoming unusable because of Read/ Writes. This is a very real possibility. The first step is to not use a swap partion/ page file. Make sure your bot has enough RAM. Another reason for Core Duo 2 is you can have up to 48Gb. Unless you really do something to exacerbate the flash wear the vast majority of consumer grade flash should last just fine with this setup it has about (500,000 writes per bit). I’d give a ballpark estimate of 5 years of heavy use. If you’re going to write a lot to the drive, you might want to pay up for industrial grade flash (5,000,000 writes per bit, much better wear-level handling, and more spare bits). dvnation.com/nand-flash-ssd.html At $300 the PQI 4Gb IDE DOM isn’t as cheap as a consumer grade Compact Flash, but it will give you at least 10 years unless you really trash it on purpose. An alternative is to use a filesystem designed for flash. This is what OpenWRT and many other embedded Linux distros do to help minimize flash wear. This makes your root partition JFFS2 or SquashFS (two filesystems designed to operate on mainly in RAM and to rarely write to the filesystem), though you now need even more RAM. I don’t think stock Debian supports this (the installer’s mkfs probably can’t do those), and I’ve never personally tried this, but I’m sure its easy to do as OpenWRT is Debian based.
Finally, I would never rely on Linux being able to do realtime stuff on a PC bot. Using a Pentium M GPIO to do PWM is highly wasteful if not bad for a whole lot of other reasons. If you were running Linux on an embedded ARM where it was the only prcessor in the bot, things would be different. However, using the SCC-32 or other servo and motor controllers which are realtime embedded will be fine, I’m assuming this bot isn’t for use in ultra critical application. Judging by how many serial ports you wanted, I’m guessing you already planned to do this.
Hope this helps…
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I am planning to use a Linux based controller for a robot at some point in the future. Are you absolutely tied to using a mini-itx motherboard?