1. Minimum Requirements
The minimum system to run LinuxCNC and Ubuntu may vary depending on the exact usage. Stepper systems in general require faster threads to generate step pulses than servo systems. Using the Live-CD you can test the software before committing a computer. Keep in mind that the Latency Test numbers are more important than the processor speed for software step generation. More information on the Latency Test is here.
Additional information is on the LinuxCNC Wiki site:
LinuxCNC and Ubuntu should run reasonably well on a computer with the following minimum hardware specification. These numbers are not the absolute minimum but will give reasonable performance for most stepper systems.
700 MHz x86 processor (1.2 GHz x86 processor recommended)
384 MB of RAM (512 MB up to 1 GB recommended)
8 GB hard disk
Graphics card capable of at least 1024x768 resolution, which is not using the NVidia or ATI fglrx proprietary drivers, and which is not an onboard video chipset that shares main memory with the CPU
A network or Internet connection (not strictly needed, but very useful for updates and for communicating with the LinuxCNC community)
Minimum hardware requirements change as Ubuntu evolves so check the Ubuntu web site for details on the LiveCD you’re using. Older hardware may benefit from selecting an older version of the LiveCD when available.
2. Problematic Hardware
Laptops are not generally suited to real time software step generation. Again a Latency Test run for an extended time will give you the info you need to determine suitability.
2.2. Video Cards
If your installation pops up with 800 x 600 screen resolution then most likely Ubuntu does not recognize your video card or monitor. Onboard video many times causes bad real time performance.