I have an i5-9600k @4.7GHz w/16GB ram, and even the basic things I run in LTspice take a long time, for a few hundred milliseconds of transient analysis.

Does LTs benifet from the CPUs with hyperthreading ? As fast as my CPU is, w/o HT it can be pretty slow at some stuff. CPU usage was 65%, 1.5GB of ram, nothing of consequence in the backgnd. Can I change some settings (in LTs) to increase CPU usage ?

 

I have an i5-9600k @4.7GHz w/16GB ram, and even the basic things I run in LTspice take a long time, for a few hundred milliseconds of transient analysis.

Does LTs benifet from the CPUs with hyperthreading ? As fast as my CPU is, w/o HT it can be pretty slow at some stuff. CPU usage was 65%, 1.5GB of ram, nothing of consequence in the backgnd. Can I change some settings (in LTs) to increase CPU usage ?

It depends...

post your circuit

eT

 

Post the .asc file of your circuit.

 

In the Control-Panel/Spice tab there is a setting for 'Max threads'. The default value is 4. I assume that's relevant to 'hyperthreading'.
There are various tricks for speeding up sims (not always advisable or practical and usually at the expense of simulation accuracy). Here are a few to try :-
1) Break down your circuit into stages/modules and simulate one at a time,
2) Don't bother simulating, say, a '555-based square-wave generator driving something else if a default Pulse voltage source will suffice as the generator,
3) Use the 'Skip initial operating point solution' option in the simulation command setting,
4) In the Control-Panel/Spice tab give one or more tolerance settings a wider value,
5) Give voltage sources some nominal series resistance,
6) Give inductors some parasitic resistance/capacitance.

 

I have an i5-9600k @4.7GHz w/16GB ram

? OS2, MacOS, Win, Linux, BSD, Custom written OS

?? i donno what the following list can reveal about your sys

• https://pc-builds.com/calculator/
• https://www.userbenchmark.com/Software

if there is anything (inadequate drivers) to (mis configured system components/parameters) -- it can impact the performance

. . . disable your LAN boards
... disable/unplug all external devices not essential for running the LTSpice
... disable desktop animated effects / screen fonts smoothing ... etc.
compare your speed against prev. cfg.