VLP80 (Variable Length Instruction Processor)

32 bit VLP80-32 / 16 bit VLP80-16

A Z80 binary compatible processor core implemented  with an efficient RISC architecture. Z80 commands are executed in fewer clock cycles,  the VLP80 is a high speed  Z80 equivalent. The VLP80 reads in instructions in 2 or 4 byte units and stores them in it's prefetch buffer. Therefore we do not need so many instruction fetch cycles and we increase processing speed.

No matter what the instruction length, 1 byte or 4 bytes, instructions are decoded in one clock cycle. Furthermore a 2 stage pipeline structure enables instruction execution to be carried out at the same time as instruction decode.

A new design of ALU allows most instructions to be decoded in one clock cycle, so Z80 CISC instructions are executed with the same efficiency as RISC instructions.
 

Features :

• 2 selectable sizes of data bus 16 bit or 32 bit.
• 16 byte pre fetch buffer results in fewer necessary fetch cycles.
• Decodes instructions of between one and four bytes at one time.
• High speed processing using RISC architecture :
Register to register operations take one clock cycle.
Register to memory operations take two cycles.
• 2 stage pipelined processing.
• Harvard Architecture option for 16 bit processor increases processing speed.
• Z80 binary code can be used without modification. But at higher speed.
• The many third vendor development tools for use with the Z80 processor can be used without modification with our processor.

Performance :

Using a cross compiler we benchmarked our processor against HITACHI`s HD64180.

The results show our processor to execute more than 4 times as many
instructions per clock cycle as the HD64180 (both processors were
operating on a 4.9 MHz clock). Below are the times for a rather slow pi
calculation to 200 deciaml places.  

 HD64180    143 Sec.
 VLP80-16    34 Sec.

According to HITACHI there processor is 4.3 times faster than
the Z80. We estimate the Z80 would perform the same calculation in :

 Z80        630 Sec.

Package :

Circuit Scale:

Processing Efficiency: