DEC 7000/10000 AXP - Hardware Description - CPU Module

CPU Module

The Model 600 systems used the KN7AA CPU module, which contained either a 182 MHz DECchip 21064 (EV4) or 200 MHz DECchip 21064 (EV4S) microprocessor. The 182 MHz version was only used in DEC 7000 AXP, with the 200 MHz version used in the DEC 10000 AXP at first, and later in the DEC 7000 AXP. The Model 700 systems used the KN7AB CPU module containing a 275 MHz DECchip 21064A (EV45).

Other than the differences in the microprocessor used and their clock frequencies, all CPU modules also featured 4 MB of B-cache (L2 cache) and two LEVI gate arrays for interfacing the module to the LSB bus. The B-cache size of 4 MB was chosen as it was the largest size achievable with 4-bit SRAMs containing 262,144 words (128 KB) on a 128-bit system bus. The B-cache SRAMs and drivers reside on both sides of the CPU module.

The LEVI also implement the Gbus, an 8-bit bus to which hardware providing console functionality is connected to. Devices connected to the Gbus are a set of seven 128 KB (8-bit by 131,072-word) flash ROMs for storing the console program, an 8 KB (8-bit by 8,192-entry) EEPROM for storing miscellaneous parameter and log information, three devices containing two UARTs each for implementing six serial lines and a watch chip containing a time-of-year clock, 50 bytes of battery-backed-up RAM and a lithium battery rated to last for 10 years.