A method, system and computer program product implement memory performance management and enhanced memory reliability of a computer system accounting for system thermal conditions. When a primary memory temperature reaches an initial temperature threshold, reads are suspended to the primary memory and reads are provided to a mirrored memory in a mirrored memory pair, and writes are provided to both the primary memory and the mirrored memory. If the primary memory temperature reaches a second temperature threshold, write operations to the primary memory are also stopped and the primary memory is turned off with DRAM power saving modes such as self timed refresh (STR), and the reads and writes are limited to the mirrored memory in the mirrored memory pair. When the primary memory temperature decreases to below the initial temperature threshold, coherency is recovered by writing a coherent copy from the mirrored memory to the primary memory.