Sun manufactures DIMM-based memory riser cards to allow upgrades from certain previous system units. The Ultra 80 Memory Riser provides redesigned memory to eliminate parity errors caused by dissimilar memory DIMMs. It requires minimum four DIMMs, which can be installed in any bank order. DIMMs are required on both the Riser Board and the System Board. Damage to the Mictor Connectors can occur if DIMMs are installed or removed when the Riser Board is installed on the System Board. Each bank addresses 1GB of memory.