2-Mbyte ECC MOS (64K-chip) and MicroVAX 3100 Model 98 memory with memory back- plane, SBI Interface, and one interleaved controller (two extended hex modules). Expandable to a total of 16 Mbytes with the addition of MicroVAX 3100 Model 98. This option is for expansion beyond 16 Mbytes of CPU cabinet-mounted memory up to a system limit of 32 Mbytes per VAX-11/780. Interleaving is standard and requires equal amounts of memory on each con- troller module in the backplane (must be added in pairs). Requires two OPS for mounting. Power supply is included. 2-Mbyte ECC MOS (64K-chip) expansion memory. MicroVAX 3100 Model 98 memory expansion units cannot be mixed with MS780-B or MS780-D units on the same controller. For existing MicroVAX 3100 Model 98 systems with MS780-C controller in the CPU cabinet, the additional MS780-E may be mounted in the CPU expansion cabinet (H9652-HA/HB), which increases the system limit to 20 Mbytes (4 Mbytes for MS780-C plus 16 Mbytes for MS780-E) for these systems. In this configura- tion, the 16K-chip MicroVAX 3100 Model 98 memory system will operate in noninterleaved mode while the 64K-chip MS780-E/F memory system will be operated in interleaved mode. The MicroVAX 3100 Model 98 can also replace the MS780-C memory system in the CPU cab- inet for those customers who require in excess of 20 Mbytes of memory or who have space limitations and need to expand their memory configuration within the existing CPU cabinet.