Hyperthreading, hyperthread or HT... should this be enabled or disabled?

P

pdkoester

DoubleYouPea & Espee fan!
Hello all, questions for you: does hyperthreading do anything to help TS12? Should I disable or enable it? Anything about this would be greatly appreciated. :cool:
 
Red_Rattler said:
Sorry Pdkoester, any chance to summarise what it means in just a sentence or two - in understandable simple English, instead of some sort of technical speak?

Besides, I didn't go the encyclopedia website, as I thought was something to do with Trainz, itself, and still can't understand the page.
Click to expand...
think of it as additional virtual cores... also generates more heat if enabled...
 
Red_Rattler said:
Sorry Pdkoester, any chance to summarise what it means in just a sentence or two - in understandable simple English, instead of some sort of technical speak?

Besides, I didn't go the encyclopedia website, as I thought was something to do with Trainz, itself, and still can't understand the page.
Click to expand...

It has nothing to do with Trainz specifically it’s a general thing for Windows and other operating systems and is aimed at the operating system level not the program level.
Different hardware companies have slightly different terms for what I’m describing below, most computer science students may have been taught slightly different terminology but it’s the concept I’m trying to get across here.

What you think of as a CPU is actually lots and lots of transistors connected together. If you ask it to add one value to another then it has to grab the first value, grab the second value then do the addition. In the same way when you add two numbers together say 8 and 9 you end up with two digits not one so the CPU has to be able to handle all the possible values ie one two digits etc. What this means is that most of the CPU components are idle most of the time.

Now to get the most out of the CPU we break things out into tasks, grab the first value, grab the second value, add the two numbers and the CPU does this in what is called a pipeline. Generally speaking a computer program will do a number of steps or instructions in a certain order so after we have done the first grab for the first instruction we can look at the next instruction to see if it needs a grab as well. If it does we can do the grab for the second whilst the first instruction is doing the add. Translation is we are now getting through more instructions than if we had to wait for each instruction to finish completely before going on to the next.

With me so far?

Pipe lining is a fairly standard way to get more instructions through the CPU.

Another way is to have more than one core but then we have to modify the program to be able to run threads ie we assign a task to a thread and dump it on to the operating system to sort out on which core it is run. One big change in TS2009 was it used threads. This meant it was slower on single core machines since there is an overhead of splitting out the tasks but it could use more than one core.
Since Windows already knows about multi core machines what Intel did with Hyperthreading was to say to Windows, or operating system, I have twice the number of cores that I really have. Then remember the bit where most of the CPU was idle most of the time? Hyperthreading allows bits of the CPU that aren’t being used in the first thread to be used to process the second thread. Both threads run slightly slower but the overall throughput is greater.
Does it have a major impact on performance? For TS2009 driver probably not as TS2009 seems to only run two threads in perfmon during driver so on a dual core machine the operating system tends to ignore the hyperthreading side and run a thread on each core.
For TS12 CMP, lots of threading opportunities so it will use hyperthreading, again you can check this with perfmon. I wouldn’t like to speculate for TS12 in driver.

I can't think of a situation where having hyperthreading enabled under Windows would mean the machine ran more slowly.

Cheerio John
 
Last edited:
johnwhelan said:
It has nothing to do with Trainz specifically it’s a general thing for Windows and other operating systems and is aimed at the operating system level not the program level.
Different hardware companies have slightly different terms for what I’m describing below, most computer science students may have been taught slightly different terminology but it’s the concept I’m trying to get across here.

What you think of as a CPU is actually lots and lots of transistors connected together. If you ask it to add one value to another then it has to grab the first value, grab the second value then do the addition. In the same way when you add two numbers together say 8 and 9 you end up with two digits not one so the CPU has to be able to handle all the possible values ie one two digits etc. What this means is that most of the CPU components are idle most of the time.

Now to get the most out of the CPU we break things out into tasks, grab the first value, grab the second value, add the two numbers and the CPU does this in what is called a pipeline. Generally speaking a computer program will do a number of steps or instructions in a certain order so after we have done the first grab for the first instruction we can look at the next instruction to see if it needs a grab as well. If it does we can do the grab for the second whilst the first instruction is doing the add. Translation is we are now getting through more instructions than if we had to wait for each instruction to finish completely before going on to the next.

With me so far?

Pipe lining is a fairly standard way to get more instructions through the CPU.

Another way is to have more than one core but then we have to modify the program to be able to run threads ie we assign a task to a thread and dump it on to the operating system to sort out on which core it is run. One big change in TS2009 was it used threads. This meant it was slower on single core machines since there is an overhead of splitting out the tasks but it could use more than one core.
Since Windows already knows about multi core machines what Intel did with Hyperthreading was to say to Windows, or operating system, I have twice the number of cores that I really have. Then remember the bit where most of the CPU was idle most of the time? Hyperthreading allows bits of the CPU that aren’t being used in the first thread to be used to process the second thread. Both threads run slightly slower but the overall throughput is greater.
Does it have a major impact on performance? For TS2009 driver probably not as TS2009 seems to only run two threads in perfmon during driver so on a dual core machine the operating system tends to ignore the hyperthreading side and run a thread on each core.
For TS12 CMP, lots of threading opportunities so it will use hyperthreading, again you can check this with perfmon. I wouldn’t like to speculate for TS12 in driver.

I can't think of a situation where having hyperthreading enabled under Windows would mean the machine ran more slowly.

Cheerio John
Click to expand...

Thank you for this.
 
I meant sorry I asked, as it's just too technical even trying to explain it. Sure, we know what CPU is, but as for most others, . . .
 
Red_Rattler said:
I meant sorry I asked, as it's just too technical even trying to explain it. Sure, we know what CPU is, but as for most others, . . .
Click to expand...

The short answer is its a way to get more instructions through a computer in a given time period if you are running Windows and a number of other operating systems.

Bye John
 
I think we've ended up where we started: leave it alone, don't disable it! I assume that's straightforward enough? :hehe:

Paul
 
Paulsw2 said:
I think we've ended up where we started: leave it alone, don't disable it! I assume that's straightforward enough? :hehe:

Paul
Click to expand...

But sometimes it helps to know the reason rather than just be told be someone. You never know if Maggie had thought through the implications of her cuts I might still be in the UK. The interesting thing was she forced them through and they didn't even save any money. Three years later she got up in parliament and said she'd like all the computer people who left and went to North America when their jobs were cut to come back.

Cheerio John
 
johnwhelan said:
But sometimes it helps to know the reason rather than just be told be someone. You never know if Maggie had thought through the implications of her cuts I might still be in the UK. The interesting thing was she forced them through and they didn't even save any money. Three years later she got up in parliament and said she'd like all the computer people who left and went to North America when their jobs were cut to come back.

Cheerio John
Click to expand...

John,

Not sure what your comment re: Maggie Thatcher has to do with hyperthreading but has your life and career improved since moving to N. America?

Rob.
 
robd said:
John,

Not sure what your comment re: Maggie Thatcher has to do with hyperthreading but has your life and career improved since moving to N. America?

Rob.
Click to expand...

I had bigger computers to play on and I didn't have to pay for the bank bail out but Marks and Spencers closed their Canadian stores some years ago and trying to find decent pickled onions makes life hard. If I fly through Paris I don't get hit by the green Heathrow tax but last time I flew into the UK I came across some moderately aggressive UK border agency people that I could have done without and the security hassles are getting worse. I don't begrudge the armed UK police who escorted some ten terrorists with explosives off my plane but it did delay things whilst we all had to deplane, the plane searched then get back on. My pensions are confused, partially UK and partially Canadian, if I move to the states then I get inflation protection on my UK portion of my old age pension, if I stay in Canada I don't. Currently I'm not intending to cross the pond again.

The comment was more to illustrate it helps to know what you are doing and why not just do it. It was expensive selling the house and coming over to Canada, but my university got cut very heavily and I lost my job, there was a recession on so no one was hiring except Canada and they closed the doors about three months after I arrived. Practically everything electrical had to be replaced but then to find out recently it was all a waste of time because it didn't save any money but actually cost money to make the cuts came as a bit of a shock.

Cheerio John
 
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