This is an old revision of the document!
Table of Contents
68080 is a new CPU that is code-compatible with the Motorola 68k processors.
It is an affordable CPU for your classic Amigas (or Amiga compatibles) that is much faster than the fastest 68060. It is compatible with all CPUs and FPUs of the Motorola 68000 family. 1) It is designed according to modern CPU standards, is fully written in VHDL, and is intended to run on Altera Cyclone FPGAs.
AmigaOS 3.x currently recognizes this new CPU as a 68040.
- Fast, available, affordable, compatible
- Superscalar, Hyper-threaded
- Executes up to 4 instructions per clock cycle
- Two address calculation engines
- Two integer execution engines
- Market-leading code density
- Optimal cache utilization
- Separate data and instruction caches, supporting concurrent fetch/read/write per clock cycle
- Automatic memory prefetching
- Memory stream detection
- Store buffer
- Branch prediction
68080 CPU, when embedded on
FPGA chips such as
Cyclone III and
Cyclone V, is much faster than the fastest
68060. This is possible because of the advanced design of the APOLLO Core, because of large and fast instruction/data caches, and because of the very fast read/write memory access.
Below are some benchmarks done with the MiniBench2) tool for some classic Amiga machines. All tests show that the Core is much faster than a fast A1200 + 68060 @ 66Mhz - scores are all confirmed by SysInfo, SysSpeed and AIBB benchmarking tools.
|Amiga 600||ACA620||68020||16 MHz||4||+|
|Amiga 1200||ACA1231||68030||41 MHz||11||+++|
|Amiga 1200||Blizzard1230||68030||50 MHz||11||+++|
|Amiga 4000||68040||25 MHz||13||+++|
|Amiga 4000||68040||40 MHz||25||++++++|
|Amiga 1200||MK2||68060||66 MHz||65||++++++++++++++++|
|Amiga 600||Vampire 600 V2||SILVER6||x15||173||+++++++++++++++++++++++++++++++++++++++++++|
More detailed comparisons to an overclocked 68060 can be found here.
The 68080 CPU covers all the instructions and architectural designs of the classic MC680x0. It also brings some new features that make it faster. The table below shows the architectural improvements for previous 680x0 CPUs and this new one.
|Static Branch Prediction||X||X||X|
|Dynamic Branch Prediction||X||X|
|Branch Target Cache||X||X|
All integer and floating-point instructions from
MC68060 are supported.
MMU-related: Rarely used on AmigaOS.
AMMX: New 64-bit instructions
These instructions are very similar to the
AltiVec versions of them.
68080 lets you use EA as 1 source and to update 3rd registers - so normally not overwrite source registers.
- Quick Reference: PDF