Hunter said:
Nothing. People have done it and still do it. But the customers are
not really keen for these chips and some vendors are to stupid to
market them properly.
No. Many did, some still do. Among the more known are the following
two.
Azul Systems builds Java "supercomputers" based on their own Vega
chip. And got in trouble with Sun about patents.
ARM sells ARM processors with Jazell DBX (Direct Bytecode eXecution).
[ property rights stuff snipped]
There's another Java-based embedded system: the Parallaxes Javelin STAMP:
http://www.parallax.com/ProductInfo/Microcontrollers/tabid/121/Default.aspx
It uses a pretty heavily modified version of Java 1.2. The Javelin is a
micro PCB that fits in a 24 pin DIL socket, so there's no point in
having any GUI stuff, but OTOH it has been extended to deal with digital
signal lines, serial I/O and A<->D conversion. In summary, the language
subsetting involves:
single thread only
no GC
no Interfaces (only abstract classes)
subset of primitive data types (boolean, char, byte, 8 and 16
bit ints)
subset of the class library
1-dimensional arrays
Strings are ASCII, not unicode.
However, there seem to be no licensing issues.
The Javelin is pin-compatible with the BS2 BASIC stamp and, for that
matter, as the BASIC is an integer basic subset with hardware specific
extensions to handle digital signal lines and serial i/o it looks as if
the subsetting and extensions applied to both Java and BASIC are quite
similar.