Motorola 68060 (MC68060) is the fourth and the last generation of
680x0 line of 32-bit microprocessors. The 68060 has two 4-stage
pipelines, separate 8KB instruction and data caches, two Paged Memory
Management Units - one for instructions and another for data, and two
integer execution units. Like its predecessor
MC68040, the 68060 integrates
Floating-Point Unit compatible with
Motorola 68881 /
68882 co-processors. The FPU provides
hardware support only for most common floating-point instructions
and data types. All unsupported instructions and data types are
emulated in software.
Supervisor mode of the Motorola 68060 CPU differs from the 68040 due
to changes in exception processing. User mode of the Motorola 68060
is object-compatible with MC68040, assuming that the CPU uses
special software to simulate a few instructions that were present in
68040 CPU and are missing in MC68060.
The Motorola 68060 is much faster than its predecessor, mainly due
to higher clock speed, superscalar design, larger instruction and
data caches and branch prediction. Under the best conditions the
68060 can execute one integer instruction and one Floating-Point
instruction per clock cycle, or up to 2 integer instructions and one
branch instruction per clock cycle. Not all integer instructions can
be executed simultaneously. Also, the CPU cannot execute the
instructions out of order.
The 68060 CPU uses lower voltage - 3.3 Volt as opposed to 5 Volt for
68040. Lower core voltage directly translates into lower CPU power
requirements. For example, 68060 66 MHz dissipates as much power as
68040 33 MHz. In addition to lower voltage the 68060 includes other
power-saving features, such as powering down individual chip units
when they are not in use, and ability to stop the clock while saving
the contents of CPU registers.
Motorola also manufactured two low-cost versions of the 68060
microprocessor:
- 68LC060 (MC68LC060) was a low-cost version without integrated FPU
- 68EC060 (MC68EC060) was an embedded version without integrated FPU
and MMU units.
| 
