Chipsets
Initially, there was no standard chipset for the 21064 and 21064A. Digital's computers used custom application-specific integrated circuits (ASICs) to interface the microprocessor to the system. As this raised development cost for third-parties who wished to develop Alpha-based products, Digital developed a standard chipset, the DECchip 21070 (Apecs), for original equipment manufacturers (OEMs).
There were two models of the 21070, the DECchip 21071 and the DECchip 21072. The 21071 was intended for workstations whereas the 21072 was intended for high-end workstations or low-end uniprocessor servers. The two models differed in memory subsystem features: the 21071 has a 64-bit memory bus and supports 8 MB to 2 GB of parity-protected memory whereas the 21072 has a 128-bit memory bus and supports 16 MB to 4 GB of ECC-protected memory.
The chipset consisted of three chip designs, the COMANCHE B-cache and memory controller, the DECADE data slice and the EPIC PCI controller. The DECADE chips implemented the data paths in 32-bit slices and therefore the 21071 has two such chips while the 21072 has four. The EPIC chip has a 32-bit path to the DECADE chips.
The 21070 was introduced on 10 January 1994, with samples available. Volume shipments began in mid-1994. In quantities of 5,000, the 21071 was priced at $90 and the 21072 at $120.
21070 users included Carrera Computers for its Pantera workstations and Digital in some models of its AlphaStations and uniprocessor AlphaServers.
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