Query on HTSplit and CMP

Hello Folks,

 

I am trying to understand threading and HTSplit feature on BIG-IP.

 

As per https://support.f5.com/csp/article/K14358, lets consider the example of BIG-IP 3900 and 4000.

 

3900 - 1 Quad Core

 

4000- 1 Quad Core (+HT)

 

If my understanding is correct, each physical CPU on a BIG-IP device corresponds to a relevant TMM process.

 

So considering above example, Number of TMM process on either device = 1

 

Now 1 CPU considering 4 cores will have equivalent 4 threads of TMM.

 

Now the point which i am not able to relate to is:

 

TMM threads (>=11.3.0, or >=11.5.0 with HTSplit disabled):

39001 Quad-core1 TMM threads : 4 4000/4200 1 Quad-core (+HT)1 TMM threads : 8

 

TMM threads(>=11.5.0 with HTSplit enabled, default)

39001 Quad-core1 TMM threads : 4

 

4000/4200 1 Quad-core (+HT)1 TMM threads : 4

 

Why is TMM thread =4 with HTsplit enabled on 4000 ?