4c/12t cpus

[NicholasNicholasNicholas]

why dont they exist? id imagine that each of the simulated cores would be too slow, but im not sure

[RadiatingLight]

Why would they

you're talking about triple-hyperthreading, which, like you said, would make each core too slow.

 

the whole point with hyperthreading is that it uses the full potential of each core, by feeding it info faster. however, tri-threading would simply slow it down, because most programs aren't that multithreaded, and it would just be slowed by the 3rd core.

[AvocadosGuac]

Think about it. 1 core / 2 threads doesnt perform aswell as 2 cores /2 threads because the core simple cannot process 2 cores worth of information. trying to put several cores through it might slightly increase it but defiantly not alot.

[SpaceGhostC2C]

SMT beyond 2-way exists, but just not in the x86 platform as it isn't that useful for a typical PC.

[NicholasNicholasNicholas]

Just now, SpaceGhostC2C said:

SMT beyond 2-way exists, but just not in the x86 platform as it isn't that useful for a typical PC.

who makes it? ibm?

[SpaceGhostC2C]

6 minutes ago, Nickathom said:

who makes it? ibm?

Sun did some an 8-way SMT. I think there were more, including IBM, but can't remember/find them now.

 

Edit: indeed, the Power line of IBM processors has gone beyond 2-way SMT since the Power 7.

Edited June 3, 2017 by SpaceGhostC2C
Found IBM

[Jurrunio]

Because current hyperthreading already squeezed out all a CPU core can give. Adding threads is like adding a pair of arms to a worker. Having 2 arms is great, but 4 arms make them work even faster. Having 6 arms though and they'll get into each other's way.

[fjdhdhcyfhf]

you prob want to read about instruction pipelining. Ive always seen hyper-threading as an attempt to manage the shit that can occur when attempting to stuff multiple program instructions into a CPU to fully utilise every component on each clock tick. Why isnt it three? Wikipedia says under the SMT article, there are CPUs from 2 to 8-thread SMT so obviously they have done their research and found 2-threads must be a sweet spot for performance.

https://en.wikipedia.org/wiki/Instruction_pipelining

https://en.wikipedia.org/wiki/Simultaneous_multithreading

this might help you understand the two above:

https://en.wikipedia.org/wiki/X86

[Guest]

1:1 scaling on x86 isn't even achievable with 2-way HT, so it's reasonable to assume that 3-way would incur no improvement, if not a penalty in performance.