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SuperH

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The SuperH (or SH) is brandname of a certain microcontroller and microprocessor architecture. The SuperH is fundamentally a 32-bit load/store RISC architecture found in a large number of embedded systems.

History

The SuperH processor core family was first developed by Hitachi in the early 90's. Many microcontrollers and microprocessors were based on this architecture.

Hitachi was developing a complete set of instruction set upward compatible CPU cores. Originally, the SH-1 and the SH-2 were used in the Sega Saturn and Sega 32X and then later in many other microcontrollers used in many other embedded applications. These cores use a 16-bit instruction set, though register length and data paths are 32-bit, which gave it an excellent code density. At the time, memory was very expensive.

A few years later, the SH-3 core was added to this family of CPU cores extending the original cores mainly by another interrupt concept, a memory management unit (MMU) and a modified cache concept. The SH-3 core also got a DSP extension, then called SH-3-DSP core. With extended data paths for efficient DSP processing, special accumulators and a dedicated MAC-type DSP engine, this core was unifying the DSP and the RISC processor world. A derivative was also used with the original SH-2 core, then called SH-DSP.

For the Sega Dreamcast, Hitachi was then developing the SH-4 architecture. This was a massive extension of the previous cores. Superscalar (2-way) instruction execution and a parallel vector floating point unit were the highlights of this architecture. This CPU core was then also used in many chipsets for embedded applications requiring a very high performance. SH-4 based standard chips were roughly introduced around 1998.

A bit later, Hitachi and ST Microelectronics formed the IP company SuperH, Inc which was going to license the SH-4 core to other companies and was developing the SH-5 architecture, the first move of SuperH into the 64-bit area. SuperH, Inc. sold the IP of these CPU cores.

The SH-5 design supported two modes of operation. SHcompact mode is equivalent to the user-mode instructions of the SH-4 instruction set. SHmedia mode is very different, using 32-bit instructions with sixty-four 64-bit integer registers and SIMD instructions. In SHmedia mode the destination of a branch (jump) is loaded into a branch register separately from the actual branch instruction. This allows the processor to prefetch instructions for a branch without having to snoop the instruction stream. The combination of a compact 16-bit instruction encoding with a more powerful 32-bit instruction encoding is not unique to SH-5; recent ARM processors have a 16-bit Thumb mode, and MIPS processors have a MIPS-16 mode. However, SH-5 differs because its backward compatibility mode is the 16-bit encoding rather than the 32-bit encoding.

After that, the evolution of the SuperH architecture still continued. The latest evolutionary step happened around 2003 where the cores from SH-2 up to SH-4 were getting unified into a superscalar SH-X core which forms a kind of instruction set superset of the previous architectures.

Today, the SuperH CPU cores, architecture and products are with Renesas Technology, a merger of the Hitachi and Mitsubishi semiconductor groups. See further details under Renesas.

Models

Hitachi SH-3 CPU

The family of SuperH CPU cores include:

  • SH-1 - used in microcontrollers for deeply embedded applications (CD-ROM drives, major appliances, etc)
  • SH-2 - used in microcontrollers with higher performance requirements, also used in automotive such as engine control units or in networking applications
  • SH-DSP - initially developed for the mobile phone market, used later in many consumer applications requiring DSP performance for JPEG compression etc
  • SH-3 - used for mobile and handheld applications, strong in Windows CE applications and market for many years in the car navigation market
  • SH-3-DSP - used mainly in multimedia terminals and networking applications, also in printers and fax machines
  • SH-4 - used whenever high performance is required such as car multimedia terminals, video game consoles, or set-top boxes
  • SH-5 - used in high-end multimedia applications
  • SH-X - mainstream core used in various flavours (with/without DSP or FPU unit) in engine control unit, car multimedia equipment, set-top boxes or mobile phones
  • SH-Mobile - SuperH Mobile Application Processor; designed to offload application processing from the baseband LSI, this is a solution to ease system development and realise significant performance improvement.


The SuperH cores are supported worldwide by many RTOS and tool vendors.

Distinctions

  • Scalability
  • Cost efficient
  • Optimised for embedded applications
  • High performance

See Also

Debuggers

RTOS

Linux for SuperH

Linux distributions for SuperH

NetBSD on SuperH

OpenBSD on SuperH

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