4 ms·
I think there is evidence—the number of execution decoders can be much higher than x86 because fixed width instructions make that less speculative. That improve
by jtc331 5y ago
I think there is evidence—the number of execution decoders can be much higher than x86 because fixed width instructions make that less speculative. That improves out of order and speculative execution prospects.
- UncleOxidant 5y agoThis. ARM instructions are much more regular and easier to decode (meaning a smaller decoder) than x86 instructions, allowing for more instruction decoders in the M1.
- bryanlarsen 5y agoA few hundred thousand extra transistors aren't a big deal on a 20 billion transistor chip.
- djbusby 5y agoDoes this mean the chip is more "secure" like against those attack vectors (Sepcetre?) that affect some x86?
- mrDmrTmrJ 5y agoNo. As long as you're preforming speculative execution Spectre vulnerabilities will persist. (Meltdown was different and solved.) The good news is Spectre style vulnerabilities are extremely hard to use and indeed have never been observed in the wild. Also, good security practices (only run trusted code on your own dedicated machine) provide full protection against theoretical Spectre attacks.
- bryanlarsen 5y agoDecoders are less than 1% of the chip, that's not a substantive difference. Both Intel and Arm decode their instructions into micro ops, so there is no difference to out of order and speculative execution prospects because of the instruction code. The only substantive difference is that Intel provides a stronger memory ordering guarantee. This is theoretically an advantage for Arm, but there are disadvantages too, so I'd call that a wash.