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The NEC V33 (1988) was a hardwired (not microcoded) version of the 286. The decision not to use microcode might be related to the long lawsuit between Intel and
by kens 3y ago
The NEC V33 (1988) was a hardwired (not microcoded) version of the 286. The decision not to use microcode might be related to the long lawsuit between Intel and NEC over microcode.
Also, as krylon points out, RISC chips generally don't use microcode.
- MichaelZuo 3y agoThanks Ken, that's pretty fascinating info. It makes me wonder if, with modern design software, a modern 64 bit CPU could be made without any microcode either.
- monocasa 3y agoDepending on what you mean by modern, there are RISC-V cores that don't use microcode, including 64-bit OoOE cores like SonicBOOM and the T-Head C920.
- dfawcus 3y agoAccording to the datasheet, which I've just looked at, it was not a '286 equivalent. Rather it added a paging mechanism whereby a 20 bit 'linear' address was mapped to a 24 bit 'physical' address. Using 1024 16k pages, so a bit like an internal LIM 4.0 scheme, but limited to 16M total rather than 24M. It has a pair of new instructions, to enter and exit the extended mapping mode, and the mappings are only changeable when not in the extended mapping mode. So a form of memory protection. See pages 20 and 21 of the following: https://datasheet.datasheetarchive.com/originals/scans/Scans-055/DSAIH000102789.pdf https://datasheet.datasheetarchive.com/originals/scans/Scans...
- kens 3y agoYou are correct.