IBM RS64

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The IBM RS64 is a 64-bit family of processors that was used in IBM's RS / 6000 and AS / 400 servers in the late 1990s .

Cobra and Muskie

IBM introduced the Cobra or A10 processor in 1995 with a clock frequency of 50 to 77 MHz. This single-chip CPU was used in the AS / 400 and was manufactured using the 0.6 µm aluminum process.

A year later, IBM introduced the multichip CPU Muski (also called A25 or A30). This 4-way SMP CPU ran with a clock frequency of 125 to 154 MHz and was used in AS / 400 servers. It was manufactured using the BiCMOS process.

RS64

The RS64 or Apache was introduced in 1997 and was intended for the RS / 6000 and AS / 400 servers. This CPU runs with a clock frequency of 125 MHz, has an integrated 128 KB L1 cache and an external 4 MB L2 cache. The L2 cache is connected to the CPU via a 128-bit bus and runs at full clock frequency. The RS64 was manufactured using the BiCMOS process.

RS64-II

The RS64-II or Northstar was introduced in 1998 with a clock frequency of 262 MHz and an 8 MB L2 cache. The L2-cache runs at full clock frequency and is connected via a 256-bit 6XX bus (see PowerPC 620 and POWER 3 ). The CPU consists of 12.5 million transistors on a the housed mm² with an area of the 162nd The RS64-II had the designation A50 in AS / 400 servers.

RS64-III

The RS64-III or Pulsar was introduced in 1999 with a clock frequency of 450 MHz. The biggest change to the architecture was the increase of the L1 cache (data cache and instruction cache) to 128 KB. In addition, the accuracy of branch prediction has been improved. Even if the branch prediction fails, this processor only needs a maximum of one more clock cycle. Other parts of the CPU are the five-stage pipeline and the L2 cache with a size of 8 MB, which is connected by a 256-bit bus. The maximum data transfer rate of the cache is 14.4 GB / s with SRAMs clocked at 225 MHz .

34 million transistors are housed on the 140 mm² die of the RS64-III. It was manufactured using the CMOS 7S process.

In 2000, IBM introduced another version of the RS64-III under the name IStar . The only difference was the SOI manufacturing process, which allowed the clock frequency to be increased to 600 MHz.

RS64-IV

In 2000 the RS64-IV or sStar , clocked at 600 MHz (later 750 MHz) , was presented. This CPU had an L2 cache of up to 16MB and was the first mass-market processor to support multithreading . The processor consists of 44 million transistors, which are housed on a 128 mm² die. It was manufactured in a 0.18 µm process.