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Ionizing dose-rate and total dose tests have been performed on the Sperry Rand 256-MNOS (SR 2256) RAM array. Results from these tests have shown that the devices can survive dose-rate levels as high as 1.0 Ã 1012 Rad(Si)/sec (in a 2 MeV electron-beam environment) with no loss of memory data or permanent degradation in device operation. However, under certain test conditions, the "Read" and "Write" modes of the arrays can be temporarily interrupted. In the Read mode, this interruption can be induced at dose-rate levels of 4 Ã 108 Rads(Si)/sec and higher if the radiation burst is applied approximately 1 microsecond in time before the start of the "Data Output" signals. In the Write mode, disturb mechanism can be generated in a 2 MeV electron beam at dose-rate levels of 2.4 Ã 1011 Rad(Si)/sec and higher if the burst is applied at the start of the "Memory Enable" signal. Also, the total dose tests have shown that the memory arrays (while cycling through its operational modes at the maximum rates) can accumulate a total dose of gamma radiation in excess of 1 Ã 105 Rad(Si) and survive. At reduced cycle rates, the arrays can operate and survive up to 3 Ã 105 Rad(Si).