> ECC wasn't pervasive in mainframes also. I remember hearing of a problem with a 3081 which turned out to be cosmic rays (really) which occaisionally changed bits in a channel buffer cache... which had neither parity nor ECC.
The first machine I know of that detected single bit errors throughout the system was the Hitachi S7 - roughly equivalent to the 3083. You can get single bit errors with no external influence at all - just from quantum mechanics. You never know where an electron realy is - it's a probability thing. There is a chance that all of the electrons constituting a charge will jump to the left at once - creating a false zero or one at the output to the gate. I remember a discussion with a CPU designer. "How often does this happen?" "Every million years or so with these transistors, more often with the smaller ones we plan in the future." "Uh huh. So why is it a problem?" "Nineteen transistors per bit, eight bits per byte, 64MB. One single bit every couple of hours." That was about 1985. I liked the microcode store recovery system. There were two banks with identical contents, interleaved for speed. If a single bit error occured, the machine just waited for the next half-cycle and took the value from the other bank. -- Phil Payne http://www.isham-research.com +44 7785 302 803 +49 173 6242039
