NEED
Our client had new requirements for an Extended,
Industry Standard Architecture (EISA) software program to allow booting of a
new generation disk controller. The software system had to be compatible with
both the 68000-based control processor and an 80486 central processing unit. The
hardware system had no room for additional EPROM storage, address decoders or
other necessary support hardware.
In addition, all functions of the necessary software had to be programmable,
such as the starting address of the EPROM, and type of disk drive attached.
SOLUTION
Mitsi developed a unique hardware and software system to meet the unusual
requirements. The 80486 processor bootstrap code was placed in the 68000
processor space. After reset, the 68000 processor copied the program to a window
into the 80486 address space. Header information was simulated to make the code
appear as if were in EPROM.
When 80486 processor control was passed to the simulated EPROM, the code then
signaled the 68000 processor. The 68000 disk controller hardware then moved the
BIOS code at very high speed to 32-bit, high speed system memory. This 'phantoming'
of the BIOS greatly increased processing speed.
Disk controller functions were supported by the moved BIOS, allowing it to
load either UNIX or MS-DOS operating systems. Access to the disk controller was
through normal INT 13 calls. This allowed the disk controller to be easily
installed into any EISA bus machine.
