Here's why I thought there might be a chance. For a PCI Mac, you can get a
PCI card with a Pentium running Windows. Although all I/O devices are
physically attached to the Mac, the two processors share them, including
monitor, keyboard, mouse, hard drives, diskette drive, CD-ROM, etc. On the
Windows side, the drivers are modified to invoke Mac functions for I/O via
PCI. On the Mac side, extensions are provided to listen for Windows I/O
commands and execute them on the Mac I/O devices.
For the next step, substitute Linux on a (single processor) PCI Pentium for
the Mac. The same PCI board could be made to work by emulating Windows I/O
in Linux, instead of in MacOS.
Supposing we have that working, now substitute a dual-processor Pentium for
the two Pentiums linked by PCI, and substitute the memory bus for the PCI
bus. Allocate different regions in memory for Windows and for Linux, and
have the Windows drivers communicate through shared memory rather than
through PCI.
With suitable support in Linux, could this work?