I was googling around for some external RAM solutions, and came across this company called Ramtron, making what they push as F-RAM. It's similar to flash or eeprom (nonvolatile) but written at low voltage and high speed. They've got I2C and SPI varieties available. Mouser and Newark carry them, but Digikey doesn't.
Anyone tried playing around with these, or other external RAMs?
I've heard good things about the Ramtron memories, and I bought one of the NVM microcontroller eval kits a while back (still sitting on a shelf.)
In addition to higher write speed than EEPROM/Flash, the FRAM technology isn't supposed to have any limits on the number of write cycles.
Well, they say it's more robust but they don't claim infinite write cycles. Just orders of magnitude better than the flash/eeprom inside the ATmega.
Their specs for the number of write cycles keep going up. I think it jumped about 3 orders of magnitude from the first time I looked I think they claimed 109 writes; now it's 1012. FLASH tends to be in the 105 to 106 write cycle range. I'd like to play with some, just haven't placed an order with anyone that stocks them yet.
The Atmel dataflash line looks interesting, too. With two SRAM buffers, one can write at bus speed pretty much continuously and let the internal architecture absorb the FLASH delays.
-j
Just noticed this: Parts: 32KB SPI SRAM Memory (23K256) | Hackaday
I have previously looked at using something like these (both available as DIP) via a I/O expander but haven't gotten to implementing anything yet:
--Phil.
Yeah, I saw those yesterday. If they ran on 5V (or had 5V tolerant inputs) I'd have some on the way already. I'm surprised they put them in DIP packages - looks to me like they're remembering us hobbyist types.
-j
You should be able to find plenty of "NV SRAM" modules in dips or other parallel access packages, in 5V as well as 3V versions. They were/are pretty common in large embedded systems for storing configurations and such. I must have dozens pulled from cisco Routers in the dumpsters (although, come to think of it, many of those are probably getting close to their expected battery lifetime.)
The parallel address and data buses are a real pain to deal with in a modern microcontroller-centric world 
Yeah, there are lots of parallel versions - got a tube of milspec parts someone donated at work.
The new Microchip part is serial (SPI) interfaced, though - much more Arduino friendly (other than the 3.3V thing).
-j