Alpha 21164
It was introduced in January 1995, succeeding the Alpha 21064A as Digital's flagship microprocessor.
First silicon of the Alpha 21164 was produced in February 1994, and the OpenVMS, Digital UNIX and Windows NT operating systems were successfully booted on it.
The final Alpha 21164, a 333 MHz version, was announced on 2 October 1995, available in sample quantities.
Digital used the Alpha 21164 operating at various clock frequencies in their AlphaServer servers, AlphaStation workstations.
[1] The Alpha 21164 is a four-issue superscalar microprocessor capable of issuing a maximum of four instructions per clock cycle to four execution units: two integer and two floating-point.
A non-pipelined floating-point divider is connected to the add pipeline.
The D-cache is dual-ported, to improve performance, and is implemented by duplicating the cache twice.
The secondary cache, known as the S-cache, is on-die and has a capacity of 96 KB.
An on-die secondary cache was required as the 21164 required more bandwidth than an external secondary cache could supply in order to provide it with enough instructions and data.
[4] The cache required two cycles to access due to its large area.
[5] The S-cache, due to the large physical area required, was implemented in two halves which flank the I-box, E-box, F-box and M-box.
The Alpha 21164 contains 9.3 million transistors on a die measuring 16.5 by 18.1 mm (299 mm2), which was close to the maximum limits of the process.
The Alpha 21164 is packaged in a 499-pin ceramic interstitial pin grid array (IPGA) measuring 57.40 by 57.40 mm.
The 600 MHz version was introduced on 31 March 1997, shipping in volume quantities.
Samsung Electronics signed a deal with Digital in June 1996 to second source the Alpha 21164A and the company was the only one to fabricate the 666 MHz model.
Users of the Alpha 21164A included Cray Research, Digital, Network Appliance (now NetApp), and DeskStation.
The most notable change was the inclusion of Byte Word Extensions (BWX), an extension to the Alpha Architecture designed to improve byte and word accesses.
The microprocessor was jointly developed by Digital and Mitsubishi Electric Corporation, and both companies fabricated the design.
Major changes are the omission of the S-cache, a larger I-cache, and the inclusion of Motion Video Instructions (MVI), an extension to the Alpha Architecture which introduced single instruction multiple data (SIMD) instructions for improving the performance of MPEG encoding.
The I-cache was doubled in capacity to 16 KB from 8 KB to compensate for the lack of S-cache, as the Alpha 21164 relied on the S-cache to complement the I-cache in order to provide enough bandwidth to achieve adequate performance.
A derivative of the PCA56, the PCA57 was designed and fabricated by Samsung Electronics in a 0.28 μm CMOS process.
The PCA57 was introduced in late 1998 and operated at clock frequencies of 533, 600 and 666 MHz.
The 21171, also known as Alcor, was the first chipset for the 21164, introduced in January 1995 alongside the microprocessor it supports.
The 21171 is an upgraded DECchip 21071 modified to support the new system bus protocol the 21164 uses.
Polaris is a system controller developed by VLSI Technology for personal computers that supports the 21164A and 21164PC microprocessors.
Users of Polaris included Digital, for its AlphaPC 164RX motherboard.
