Shortly after the release of Starbirds it turned out that Starbirds didn't work on every system. In fact, we discovered that only BlizzardPPC equipped systems were affected by this problem. Using a patch Starbirds can be made working also for these systems.
Now the big question is, why were only BlizzardPPC systems affected, while systems with CyberStormPPC hardware didn't have similar problems? What's the difference between those hardware systems and what could be the reason why such old games don't work anymore?
The answer to these questions is obvious: the big difference between those accelerator cards is the Flash ROM and its content. And indeed, it turned out that the Flash ROM was responsible for Starbirds not working anymore. Now we will discuss the reasons in greater detail and the BlizzardPPC users will learn, what all is caused by this Flash ROM.
The BlizzardPPC flash ROM contains, among other things, the ppc.library and the 68040.library/68060.library. The problems caused by the ppc.library (especially for WarpUp) don't have to be discussed anymore, they should be well-known. But what is still not known widely are the consequences which arise from starting the 68040.library/68060.library at boot time. These libraries' job is to setup features of newer processors so that the full power of the hardware can be provided.
For every system with the exception of the BlizzardPPC-equipped systems, the 68040.library/68060.library is started when the 'SetPatch' command is executed in the startup-sequence. This has the consequence, that the AMIGA still behaves mostly like a Low-End-AMIGA directly after boot time. For the BlizzardPPC systems things change completely, those systems are forced to enter a 'high end mode' directly after boot, and that's the reason why there is such a big incompatibility to old software, mostly to old games.
The following operations, which are done by the 68040.library/68060.library at startup, lead to a big incompatibility to old software:
We strongly believe that very few owners of BlizzardPPC hardware really know that not the CPU is responsible for the low compatibility, but the Flash-ROM.
For Starbirds we were able to write a patch which solves the problem. This patch resets the VBR to zero, switches the data cache off and switches the MMU off and sets the registers to some neutral value. For many other games it is almost impossible to add such patches, because these are started from boot-block. Such games have no chance on BlizzardPPC systems until a new Flash-ROM comes out, which doesn't contain the ppc.library/68040.library/68060.library anymore.