* Volker Armin Hemmann <volkerar...@googlemail.com> wrote: > the CPU. All CPUs use microcode. For decades. Google, or go straight to > wikipedia. > http://en.wikipedia.org/wiki/Microcode
Borroughs' large systems (b6500+) were designed as microcode machines from ground up, which essentially interpreted an algol bytecode (the whole OS was directly implemented in assembler, w/o any machine specific assembler code). Paired w/ their entirely stack-based architecture (there were no program-visible registers) they could easily do massive-multiprocessing (everything's reentrant by design), 24/7 uptime even w/ hw replacements/upgrades and cpu improvements w/o ever having to recompile. Their successors (now Unisys) are called emode machines - quite the same approach as nowadays w/ Java (interpreter/JIT). BTW: I'm currently designing an emode/microcode-base computer architecture built on an matrix of nanocores, they don't have a concept of main memory, instead a relatively large (linear addressable) register memory, part of the register space is shared with neighbours (multiport-RAMs). These are programmed by an horizontal microcode, which is decoded by an static demux, that directly connects registers to an micro-ALU (so there're no additional load+store cycles) ... cu -- ---------------------------------------------------------------------- Enrico Weigelt, metux IT service -- http://www.metux.de/ phone: +49 36207 519931 email: weig...@metux.de mobile: +49 151 27565287 icq: 210169427 skype: nekrad666 ---------------------------------------------------------------------- Embedded-Linux / Portierung / Opensource-QM / Verteilte Systeme ----------------------------------------------------------------------
