Over the years there have been a few CPUs designed to directly run a high-level programming language, the most common approach being to build a physical manifestation of a portable code virtual machine. An example might be the experimental Java processors which implemented the JVM. Similarly, in 1976 Itty Bitty Computers released an implementation of Tiny BASIC which used a simple virtual machine, and to celebrate 50 years of Tiny BASIC, [Zoltan Pekic] designed a CPU that mirrors that VM.
The CPU was created within a Digilent Anvyl board, and the VHDL file is freely available. The microcode mapping ROM was generated by a microcode compiler, also written by [Zoltan]. The original design could execute all of the 40 instructions included in the reference implementation of Tiny BASIC; later iterations extended it a bit more. To benchmark its performance, [Zoltan] set the clock rate on the development board equal to those of various other retrocomputers, then compared the times each took to calculate the prime numbers under 1000 using the same Tiny BASIC program. The BASIC CPU outperformed all of them except for Digital Microsystems’ HEX29.
The next step was to add a number of performance optimizations, including a GOTO cache and better use of parallel operations. [Zoltan] then wrote a “Hello World” demo, which can be seen below, and extended the dialect of Tiny BASIC with FOR loops, INPUT statements, multiple LET statements, the modulo operator, and more. Finally, he also extended the CPU from 16-bit to 32-bit to be able to run an additional benchmark, on which it once again outperformed retrocomputers with comparable clock speeds.
We’ve previously seen [Zoltan]’s work with FPGAs, whether it’s giving one a cassette interface or using one to directly access a CPU’s memory bus. BASIC has always been a cross-platform pioneer, once even to the extent of creating a free national standard.
Just over 40 years ago, I looked at doing this kind of thing with AMD2900 bit slices. I abandoned the idea for two reasons.
Firstly, while it would have been a speed increase over existing processors (80386, 68000), that advantage would have disappeared in a couple of years. Now that processors are no longer improving that rapidly, that might not be true nowadays.
Secondly, advanced compiler techniques (e.g. peephole optimisation of the IL instructions) gave even larger performance increases. Nowadays such techniques – and many more – are widespread.
Nonetheless, creating a processor is a standard “fantasy” for hardware engineers. For software engineers the equivalent is creating a language. Both are fun and harmless, but shouldn’t be confused with useful :)
I’ll also note that comparing different processor’s performance normalised to clock speed was (and is) highly misleading, since some processors require many more clocks to execute one instruction. The 1802 is and example.