 A maximal configuration had 512 MB of memory.The number of I/O buses supported varied, with the Model 410 and 420 supporting two XMI, ten CI and eight VAXBI; while the Model 430 and 440 supported four XMI, ten CI and 14 VAXBI.The VAX 9000 was a multiprocessor and supported one, two, three or four CPUs clocked at 62.5 MHz (16 ns cycle time).