WarpOS

WarpOS was a multi-tasking kernel for the PowerPC architecture developed by Haage & Partner for the Amiga computer platform in the late 1990s and early 2000s. It ran on PowerUP accelerator boards developed by phase5 which contained both a Motorola 68000 family CPU and a PowerPC CPU with shared address space. WarpOS ran alongside the 68k-based AmigaOS, which could use the PowerPC as a coprocessor. Despite its name, it is not an operating system (OS), but a kernel; it supplies a limited set of functions similar to those in AmigaOS for using the PowerPC. When released its original name was WarpUP, but was changed to reflect its greater feature set, and possibly to avoid comparison with its competitor, PowerUP.

It was developed by Sam Jordan using 680x0 and PowerPC assembler. It was distributed free of charge.

History

In 1997, Phase5, an Amiga hardware manufacturer, launched their range of PowerPC (PPC) accelerators for the Amiga. Because AmigaOS was not yet PowerPC native, as a stopgap measure the PowerUP boards were dual-processor boards, incorporating the PPC and a 68K processor (68LC040, 68040 at 25 MHz or 68060 at 50 MHz). They carried the PowerUP kernel on board in an EPROM, a similar kernel designed to allow AmigaOS applications to use both PPC and 68k applications through an API library called ppc.library. AmigaOS still required a 68K processor, while the PPC was in effect used as an extremely fast coprocessor that carried out specific instructions.

Unfortunately, this caused significant slowdown when the OS task switches between the 68K and PPC (a context switch), because CPU caches had to be flushed to maintain memory integrity. The more CPU switches occur in an application, the more the slowdown, often so seriously that it was pointless to use the PPC processor at all, being slower than the 68k native binary. The main workaround for this was simply to avoid as many 68k OS calls as possible, or to group them together, but it was difficult and time-consuming for developers to do this.

WarpOS was launched as a controversial alternative to Phase5's PowerUP kernel, but eventually became the most used and nominally the standard PPC kernel on AmigaOS.

Features

WarpOS had similar features to PowerUP, but with some major differences. Most pertinently, it used the PowerOpen ABI, in contrast to PowerUP which used the newer and better supported SysV, which ensured both kernels could not be directly compatible.

From version 14, the WarpOS kernel used a slightly different multitasking scheduler than AmigaOS (or PowerUP), based on that in Unix systems with "nice" values as well as priorities for its own tasks and processes. This was meant to ensure that all tasks got CPU time, and weren't "starved" of CPU time by compute-intensive tasks (as was the case with the original AmigaOS scheduler). However, this was ineffective as it was still limited by the native AmigaOS scheduler and it did create extra difficulties synchronising with the 68k side (particularly for sound). In version 15 WarpOS introduced a concept called atomic tasks. Atomic tasks are non-interruptible, and scheduling does not take place unless the task explicitly allows to do so.

WarpOS also had an inbuilt debugger which could be sent to dump information on any crashed tasks to either console window on screen or to serial, depending on environment variables.

One of the most lauded features of WarpOS was that it continued the "hunk" format of original Amiga executables which implemented the Amiga Hunk format of executables. This format was called EHF (Extended Hunk format), and implemented the hunk type named HUNK_PPC_CODE. This allowed AmigaOS to transparently handle WarpOS executables without having to patch the OS to recognise them, which PowerUP did have to do to run its ELF fileformat. While elegant in theory, the EHF format's downfall was its lack of widespread compiler support (especially GCC), and the ELF file format was adopted by AmigaOS 4 and MorphOS.

Unlike PowerUP, WarpOS could also produce mixed (fat) binaries with both 68k and PPC code, which could run on both Amiga PPC boards and ordinary Amiga systems. This practice was very rare due to the programming complexity of doing so, but the picture datatype in AmigaOS 3.9 (a shared library that loaded, processed and dithered pictures through the AmigaOS datatypes system) was a notable example of its use. PPC equipped systems would notice an immediate large speed-up, while 68k systems and emulators would still be compatible without having crashing or installing another binary.

WarpOS had two housekeeping tasks named Defiant and Babylon5, thought to be named after the USS Defiant from Star Trek DS9 and Babylon 5, its developers being science fiction fans. These would often be reported by new users who did not know what they were appearing in tasks lists.

Controversy

Haage & Partner, an Amiga software and hardware manufacturer (which also created AmigaOS 3.9), developed a competing kernel to PowerUP called WarpUP, which they claimed would work around the context switching problem, a claim which would be bitterly challenged by Phase5. Phase5 claimed correctly that this hardware problem could not be circumvented by simply optimising the kernel and was a limitation inherent to the almost unique board design, which shared the memory bus between two CPUs of radically different families. WarpOS versions up to V7 were wrappers added around Phase5's PowerUP kernel but starting from version 8 it was its own PPC kernel running alongside AmigaOS and was renamed WarpOS.

As PowerUP was on the EPROM of the boards and Phase5 could not run at the same time with WarpOS, it had to be deactivated by a small software tool. As H&P did not have access to the EPROM, the tool had to make assumptions about the PowerUP kernel and naturally this broke in updated versions. This led to open accusations by WarpOS advocates and by the author, Sam Jordan, that Phase5 were intentionally trying to prevent WarpOS running on their boards. Phase5 also claimed that Haage & Partner abused a free developer board gifted to them to launch this competing kernel (although free, WarpOS was supported almost exclusively by H&P's commercial StormC++ compiler), and that they had reverse-engineered PowerUP to do so. H&P pointed out that it was unavoidable as long Phase5 refused to allow users to choose what kernel to put on the board EPROM, claiming that the PowerUP kernel was essential for initialising the boards on boot and erasing them would simply render the boards useless.

Worse still, users were originally only able to run one of these kernels, resulting in much duplication of effort between competing developers determined to use one or the other, often with two version of software being developed independently. Despite there being little or no real difference in performance, debugging capability, usability or stability in either system, and it had become patently clear that neither could hope to work around the hardware context switch issue, a series of claims were made on each side and much fighting in Usenet followed.

The farce generated produced a great number of hurriedly ported, often semi-functional ports of open source software from Windows, often just to "one up" the other side. Steffen Haeuser (who had gained notoriety by declaring, "ELF is a monster !!!", referring to the ELF fileformat) of Hyperion Entertainment CVBA was particularly infamous for his "political" ports being so rushed that they lacked sound or were very unstable, being released just to make up the numbers and produce a list of software greater than that of PowerUP.

The last section is biased though. The thing was, Steffen Häuser's ports only had instability when running on systems where PowerUP applications were running. Running executables from both lead to instabilities. Only systems without PowerUP-Software this did not happen (Steffen Häuser did not use any PowerUP-software). The (by MorphOS-fans) often cited "Elf is a monster" was only a funny remark to indicate that ELF-executables were quite large in size (which is actually the truth). True, some ports of Steffen Häuser lacked sound, he was not an expert on Sound programming. The intention of these port was not "political", though, but that it would be "better" that people not using PowerUP would have a port without sound available than no port at all. It was not about "creating a greater list of software".

The impasse between the competing systems was eventually ended by a PowerUP wrapper for WarpOS by Franke Wille, which allowed users to run PowerUP software on their WarpOS systems.

Legacy

The bitter infighting in the Amiga community over the two kernels, while brief, was to produce a rift that would eventually culminate in the split between AmigaOS and MorphOS, with the majority of WarpOS and PowerUP developers switching either new AmigaOS implementation respectively.

WarpOS was intended to be used as a basis for AmigaOS 4 but Haage & Partner dropped the project when their "AmigaOS 4 PPC" contract was cancelled by Amiga, Inc. in 2000. When Hyperion Entertainment took over the project they originally had the same idea, but it was later admitted by their developers that it proved very little use in modernising the OS, being written wholly in non-annotated machine code assembler.

The choice of WarpOS over its rival proved to be a Pyrrhic victory, as the standards it had developed around - namely EHF and PowerOpen - were to be wholly abandoned in later development of AmigaOS and its clones. The dual CPU model was not revisited.

AmigaOS 4 supports WarpOS applications on PowerPC 603e, 604e, 440EP, G3 and G4 based computers. MorphOS is more compatible and can run both WarpOS and PowerUP applications natively using API wrapping, despite the differences in ABI.

WarpUP

WarpUP is a high-speed kernel for PowerPC versions of Amiga.

WarpUP forms a hardware abstraction layer between the hardware and software, and ensures that the applications function correctly on PowerPC architecture. It also forms an interface between PowerPC driven hardware, and 68k compliant software, which allows the optimal exploitation of the speed of the PowerPC CPU, whilst making the porting of 68k applications as easy as possible.

A number of advantages that WarpUP claims to offer are:

• High speed communication between 68k programs and PowerPC CPUs
• Native multi-tasking, memory management, semaphores, list and tag management, signalling and message handling
• Memory protection (tasks are allowed to allocate to protected memory areas if need be)
• Virtual Signals (signals are shared between CPUs and will always be redirected to the correct CPU when needed)
• Inter-CPU messaging system (messages are passed between the CPUs when needed)
• Optimal use of the PowerPC Memory Management Unit and the PowerPC Cache
• Memory Management Unit and Exception-Handling support for applications
• PowerSave function that turns the PowerPC off if there are no applications that are using it
• PowerPC Enforcer (protects the first page of memory)
• A detailed crash requester that provides detailed information to help developers locate errors
• Integrated debugging system that enables bug tracking easier
• Specific support for highly optimized software such as games and demos
• Support for Amiga-Compliant applications
• Libraries for PowerPC native, mixed and FAT binary applications
• WarpUP is also usable for alternative developer systems such as Modula- or E-compilers with PowerPC-support. This is because objects are not mandatorily created in ELF; instead the Amiga compliant hunk format can be used as well.
• Easy to install
• Hardware independent

See also

• Amiga exec

Notes

1. ^ Warpsness problems :( Steffen Haeuser explains WarpUp kernel at comp.sys.amiga.games
2. ^ See also pages regarding history of the PPC processor on Amiga at Amiga.History site.
3. ^ EHF specifications on Haage&Partners site.
4. ^ BlizzardPPC Flash Why WarpOS and Warp3D have problems with Blizzard PPC
5. ^ Amiga Report Magazine Haage and Partner Announce WarpUP, Phase5 Blasts H&P
6. ^ comp.sys.amiga.games Steffen Haeuser comments ELF
7. ^ ppclibemu ppc.library emulation under WarpOS
8. ^ List of software projects of Sam Jordan
9. ^ Interview with Ben Hermans from Hyperion Benjamin Hermans comments WarpOS
10. ^ Jordan, S: powerpc.library/WarpOS history. 2001