Phase5

Phase5 Digital Products is a defunct German computer hardware manufacturer that developed third-party hardware primarily for the Amiga platform. Their most popular products included CPU upgrade boards, SCSI controllers and graphics cards.

Like other third-party Amiga developers, Phase5 developed a range of CPU boards utilizing Motorola 68000 family processors, which powered Amiga systems at the time. Such boards also typically featured onboard RAM controllers with access to faster and greater capacity memory.

Notably, Phase5 were unique amongst Amiga developers in offering the Blizzard PPC and CyberStorm PPC products. These boards had a unique dual-CPU design utilizing both a Motorola 68k processor and a higher performance PowerPC processor. They operated in a novel fashion where both CPUs could execute concurrently while sharing the system address space. This architecture was enforced by the fact that AmigaOS was still 68k-based at the time and the required emulation software had not yet been developed to run natively on the PowerPC architecture. This design suffered from the need to flush CPU caches following context switches between 68k and PowerPC code. From a software development standpoint, this made mixing code ad hoc and often impractical. Minimizing such context switches required a large amount of effort and planning, making adoption of mixed binaries somewhat unpopular.

Phase5 developed a PowerPC kernel called PowerUP which ran alongside the 68k-based AmigaOS. Effectively, a programmer could then utilize the PowerPC CPU as a coprocessor. German company Haage & Partner developed a competing multi-tasking kernel called WarpOS for the Phase5 PowerPC boards which operated in a similar manner, but was not code-compatible with PowerUP.

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