for you it's possible to connect some pc ram with arduino and some electronics?
Stefano
You probably wont have enough pins unless it is really small or uses a serial interface which in turn becomes slow.
On some of the XMEGA's you have dedicated ports for memory, as used in the AVR Xplain.
ok thank you
You can get some smaller parallel RAM chips from digikey - designed for microcontrollers.
Its much easier than that. The 1280/2560 supports extra ram directly.
The cerebotPlus board comes with an extra 128K RAM on board (its not an Arduino board but I have written an Arduino library and bootloader for it).
http://www.digilentinc.com/Products/Detail.cfm?NavPath=2,396,611&Prod=CEREBOT-PLUS
The RAM is contiguous above the on-chip RAM and works perfectly.
Refer to page 27 of the 2560 manual (doc2549) and it explains the external memory interface.
Once you have the Ram hooked up, its a simple 2 lines of code to enable it. Of course you loose some I/O lines (Port A).
Mark
If the 1280 supports RAM are the ports availible on the Arduino MEGA and does it use many?
If the 1280 supports RAM are the ports availible on the Arduino MEGA and does it use many?
That is a good question. The Arduino mega does not bring out traces for 16 of the chip's I/O pins. T'm sure the datasheet for the 1280 chip covers external memory and what pins are used to support that feature, just takes time to analyze it Vs the Arduino board.
Lefty
The ram connects to all of port c then a couple of pins out of each of the other ports by the look of it. I'll inspect the wiring diagram of the mega and get back to you. Damned curiosity. 
Right here it goes:
RAM,atmega,arduino
RD, PG1, Pin 40
WR, PG0, Pin 41
ALE, PG2, Pin 39
A0-7, PA0-7, pins 22 - 29
D0-7, PA0-7, pins 22-29
A8-15, PC0-7, pins 37-30