Lisa was designed to use slower, more reliable, parity memory, and other features that reduced speed but increased stability and value. Lisa is able to operate when RAM chips failed on its memory boards, unlike later Macintosh systems, reducing the cost to owners by enabling the usage of partially-failed boards. The Lisa system isolates the failed chip or chips and uses the rest of the board's RAM. This was particularly important given the large number of individual RAM chips Lisa used in 1983 for a consumer system (and around $2500 in cost to Apple per machine). RAM could be upgraded to 2 MB.