Cheapest ARM with an MMU

The Atmel AT91SAM9260B comes in a LQFP package and may be a little bit lower in price than the SAM9G20. It has a MMU and the same peripherals as the SAM9G20 but runs at 200 MHz rather than a max of 400 MHz. Pay attention to the details in the Atmel Application note Schematic Checklists and you will be successful.

You could also try the AT91SAM9XE512 with flash on-chip. But 512KB isn't going to be enough even for uCLinux, so the most cost effective thing to do is use the flash-less SAM9G20 or SAM9260B with external flash and SDRAM.

http://www.atmel.com/at91

I think the answer is chips in the ARM926EJ-S family, like the AT91SAM9G20. The G20 costs around $10 in relatively low quantity, and it has an MMU. Unfortunately, it's only available in a BGA package, and you'll need external memory.

The good news is that the ball pitch on the G20 is 0.5 mm (edit: there's a 0.8 mm pitch version too), which is just within the limit of what most assembly houses will do without a surcharge. If you go to an ARM Cortex A8, like the OMAP35xx, you have to deal with 0.4 mm ball pitch.

There are at least 5 companies that are making SBCs using the G20. Here are a few:

• Emac SoM-9G20, Illinois, USA
• Taskit Stamp9G20, Berlin, Germany
• Propox MMnet1002, Poland

(I'm actually working on an open hardware board based around this chip, but it won't be ready for a few months at least. But that at least explains why I have all this crap in my head!)

The AT91RM9200 used to be a popular choice (ARM9 + MMU). It's non-BGA, but doesn't have integrated RAM/Flash.

http://opencircuits.com/Linuxstamp