On Wed, Feb 23, 2011 at 6:33 AM, Tony Firshman <[email protected]> wrote:
> The one that rescued a vast number of QLs I repaired was his ram check and > error display. The ram check is writing rom images into ram, and reading > back. He seeded this. Why? Well if a zero is written to a dead ram bit, > zero is *always* read back, even if the bit is dead. > The correct, proper and full way to check dynamic RAM, learned from my mainframe-supporting days, is this: Write %00000000 to each location and read back. Write %11111111 to each location and read back. Write %00000000 to each location and read back. Write %10101010 to each location and read back. Write %01010101 to each location and read back. Write %11111111 to each location and read back. Write %00000000 to each location and read back. Write %11111111 to each location and read back. That's the quick way. The long form is also to write: %11011011 %10110110 %01101101 (ie: 11011011 rotated left each position) Then repeat rotating to the right each position, while writing complimentary and opposing data in adjacent bytes, noting that "adjacent" means physically adjacent, so you need to know something of the organization of the memory in the core/die. Shortcuts: %00000000 = 0 %01010101 = 85 %10101010 = 170 %11111111 = 255 Fun times! Dave _______________________________________________ QL-Users Mailing List http://www.q-v-d.demon.co.uk/smsqe.htm
