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That's Intel's term from the Intel® 64 and IA-32 Architectures Optimization Reference Manual. MS-ROM stands for microcode sequencer ROM. Complicated instruction
by CalChris 8y ago
That's Intel's term from the Intel® 64 and IA-32 Architectures Optimization Reference Manual. MS-ROM stands for microcode sequencer ROM. Complicated instructions aren't decoded from x86 into μops. They're read from the MS-ROM (what Fog calls the microcode ROM). They pollute the μop cache. Basically, they support the really complex instructions but that's it.
Clearly the ROM is a ROM and read-only and I mistakenly said that user microprograms would be written there. No, they'd be written to a WCS, Writeable Control Store.
All that said, the Intels + ARMs of the world would hate this idea. You'd be eeking out a wittle bit of performance at significant support cost. They'd just tell you to buy a faster or another CPU.
User programmable WCS was an idea from the 80s. But now, it's a bad idea. If it were a good idea then Microsoft or Google or Amazon would be all over it because they have the capital, the leverage and the need to do it. Yet they don't.