Jazz (computer) - Definition and Overview

The Jazz computer architecture was a motherboard and chipset design originally developed by Microsoft for use in developing Windows NT. The design was eventually used as the basis for most MIPS-based Windows NT systems.

In part because Microsoft intended NT to be portable between various microprocessor architectures, the MIPS RISC architecture was chosen for the initial development platform for the NT project in the late 1980s/early 1990s. However, around 1990, the existing MIPS-based systems (such as the Turbochannel-equipped DECstation or the SGI Indigo) varied drastically from standard Intel personal computers such as the IBM AT—for example, neither used the ISA bus so common in Intel 386-class machines.

For those and other reasons, Microsoft decided to design their own MIPS-based hardware platform on which to develop NT, which resulted in the Jazz architecture.

The Jazz architecture includes:

• a MIPS R4000 (MIPS III) or compatible microprocessor
• an EISA bus
• a framebuffer for video output (the G364 framebuffer)
• PS/2 connectors for mouse and keyboard
• onboard 16-bit sound system
• onboard Sonic ethernet
• onboard NCR 53C9x SCSI chipset for hard disk and CD-ROM interface
• standard IBM AT serial and parallel ports
• IBM AT-style time-of-year clock

This design was simple enough and powerful enough that a majority of Windows NT-capable MIPS systems were based on modified versions of the Jazz architecture. A list of systems which were based on Jazz includes:

• Acer PICA
• DeskStation Tyne
• MIPS Magnum (R4000 PC-50 and SC-50 versions)
• NEC RISCstation
• Olivetti M700

The Jazz systems were designed to partially comply with the Advanced RISC Computing (ARC) standard, and each used the ARC firmware to boot Windows NT. Other operating systems were also ported to various Jazz implementations, such as RISC/os to the MIPS Magnum. External links:

• Linux-MIPS Jazz (http://www.linux-mips.org/wiki/index.php/Jazz) article