AMD Hyperthreading?

H

Hvatum

Gawd
Joined
Apr 21, 2005
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882
Just wondering why AMD doesn't have anything like Hyperthreading. Does Intel have a total Patent stranglehold on it or is it just not worth the research costs?

This has always nagged me so I'd like to know exactly what the deal is.
 
I dont know the answer to your HT question and I also would like to know.

Maybe they dont need it...and also the X2 is a true multiprocessor chip and blows the Pentium D out of the water. Maybe they put their effort towards that instead???
 
Someone with more technical knowledge will come in a clean up my mistakes, but from my understanding it has to do with the efficiency of the processor design. Longer pipeline = harder to keep filled with good predictions for what is coming next. So, you split it in half with hyperthreading. AMD's design is to use a shorter instructions pipeline, so this is not a concern. This is also the reason why you can't compare ghz to ghz
 
HT was a band-aid for the insanly long pipe in the P4
with out large parts of the pipeline sit idle

the A64s pipe is much shorter and doesnt have the issues with stages sitting idle

short awnser is it doesnt need it
 
fwiw AMD holds some patents on SMT, and I believe so does Sun and IBM.

AMD doesn't need SMT, there are too few 'bubbles' in the pipeline to fill and, even more so with PPC. Intel will eventually drop it when they move their entire lineup over to multi-core Pentium M designs. Dual core has effectively made it redundant.
 
Asian Dub Foundation said:
or intel patented it?
Click to expand...

Research into Symmetric multithreading (under one name or another) dates back a good 20 years. Starting in the acedemic world and later by IBM, SUN, Intel, et al.
Intel if they wanted, could patent their implementation of HT, but not the idea of SMT.

Why doesn't AMD have an SMT enabled chip?
The same reason Pentium M doesn't.
The execution core part of K8 is pretty much lifted straight out of K7. AMD wouldn't have even considered SMT when they were designing K7, and rebuilding the core to support SMT now would be a signifigant investment in time, effort and money. AMD opted to make the K7 core more efficient in other ways - better schedueling, on die memory controller, better SSE* support - rather than going down a path that offered fairly limited returns because of
1. the few programs that really took advantage of multithreading at the time
2. the advantage dual core chips have over SMT chips in multithreaded apps.
 
LENGTH DOESN'T MATTER!
(That's what she said)


it's the width.. there's a bunch of width in the cores that does not get used in some cases, so intel made up a quick way to for the scheduler to throw another set of instructions through them.
why didn't amd do it? my guess is that the way the K8's cache is set up, it would have incurred larger hits, negating the usefulness... speaking of usefullness, we all know what happens to HT in a server environment, where it seems like it should thrive :D
width definitly isn't the issue, as the K8 is even wider than netburst:
http://www.tt-hardware.com/img/processeurs03/a64_02.gif
 
This is very interesting.

SO Eclipse - you are saying that instead of how long the pipes are...like 30 stages or whatever, they take teh width, lets say 64kb wide (I have no fucking clue what it really should be), and HT cuts in in half to make two logical 32kb wide pipes?

And so the length of the pipes is irrevelant?
 
if you look at the block diagram of K8 i linked, you'll see what i mean by width...
3 decode paths, 4 schedulers, and array of *lu's... ;)
 
nish this post in another post.

PS: I still dont get it...those pictures make no sence to me, I just gave up.
rolleyes.gif
 
HighwayAssassins said:
nish this post in another post.

PS: I still dont get it...those pictures make no sence to me, I just gave up.
rolleyes.gif
Click to expand...

LOL :p
 
well for what it's worth. HT is the reason I stopped buying AMD chips and purchased only intel until recently. I do way too much multi tasking and when using any chip with HT vs a chip that has only one logical processor the difference is massive. If you are doing something really processor intensive with a single core cpu without HT then the whole machine grinds to a halt. With HT, I rarely had that problem. The only thing bringing me back to AMD is the dual core. Most people don't realize that raw single thread speed isn't everything. ^^
 
sdadept said:
well for what it's worth. HT is the reason I stopped buying AMD chips and purchased only intel until recently. I do way too much multi tasking and when using any chip with HT vs a chip that has only one logical processor the difference is massive. If you are doing something really processor intensive with a single core cpu without HT then the whole machine grinds to a halt. With HT, I rarely had that problem. The only thing bringing me back to AMD is the dual core. Most people don't realize that raw single thread speed isn't everything. ^^
Click to expand...
Its true...when using DVD Shrink to encode DVDs, my system becomes just about unusable. If an app is open, its fine, but forget about opening sometihng new.

The thing is, 99% of the time my system isnt at that state. Also, that is at lower clockspeeds. at clocks > 2.6, I sware it felt like I had hyperthreading.

when it comes down to it, raw speed is more important to me than multitasking, because I can multitask fine with this CPU...and I game, therefore there is only one option.

To edit what you said a little, I think most people don't realize that hyperthreading isnt everything. When I see a commercial that says "With HT Technology" I just want to puke. And yes, I know I am an AMD fan boy...I can accept that.
 
HighwayAssassins said:
Its true...when using DVD Shrink to encode DVDs, my system becomes just about unusable. If an app is open, its fine, but forget about opening sometihng new.
Click to expand...

If an app is hogging your system simply lower its priority. You never notice folding, seti, dnet etc, progs that always use 100% CPU, hogging your system simply because they run at the lowest priority.
 
leathered said:
If an app is hogging your system simply lower its priority. You never notice folding, seti, dnet etc, progs that always use 100% CPU, hogging your system simply because they run at the lowest priority.
Click to expand...
Hm good idea....
 
Enjoicube said:
yeah, but what about those who can't afford it.
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With the entry price of a S939 dual core CPU under the $300 mark anyone planning to build a new rig or planning an upgrade to an existing S939 setup can afford dual core.
 
uh....the box my processor came in (Athlon 64 3200+) says:

"with HyperTransport Technology"

it's not "threading" but looks pretty damn close to the same thing to me.
 
enigmamdw said:
uh....the box my processor came in (Athlon 64 3200+) says:

"with HyperTransport Technology"

it's not "threading" but looks pretty damn close to the same thing to me.
Click to expand...


thats what AMD uses as the system bus now
 
SKy042 said:
With the entry price of a S939 dual core CPU under the $300 mark anyone planning to build a new rig or planning an upgrade to an existing S939 setup can afford dual core.
Click to expand...


is 320 close enough to 300 for you?
you can get a 3800+ X2 for that now
 
enigmamdw said:
uh....the box my processor came in (Athlon 64 3200+) says:

"with HyperTransport Technology"

it's not "threading" but looks pretty damn close to the same thing to me.
Click to expand...

dahaha!
 
Elios said:
is 320 close enough to 300 for you?
you can get a 3800+ X2 for that now
Click to expand...
But if you know where to shop you can buy a 165 Opteron for $280 OEM and $295 retail.
 
enigmamdw said:
uh....the box my processor came in (Athlon 64 3200+) says:

"with HyperTransport Technology"

it's not "threading" but looks pretty damn close to the same thing to me.
Click to expand...


Wow I might sound really nerdy and don't take this personally but your n00bie rank is appropriate here ;)
 
sdadept said:
well for what it's worth. HT is the reason I stopped buying AMD chips and purchased only intel until recently. I do way too much multi tasking and when using any chip with HT vs a chip that has only one logical processor the difference is massive. If you are doing something really processor intensive with a single core cpu without HT then the whole machine grinds to a halt. With HT, I rarely had that problem. The only thing bringing me back to AMD is the dual core. Most people don't realize that raw single thread speed isn't everything. ^^
Click to expand...

This is only a problem in windows because the damn Kernel isn't pre-emptible.

If a process is waiting for a response from a kernel level resource in Windows and that process has high priority everything else grinds to a hault until that process completes it's given task. The kernel will essentially give that process highest priority for what a long time even though it might not be doing anything but writing to the disk at the time. But since it's a kernel level operation (Disk IO) it can't be displaced by any user level process such as your MP3 player or video game. Your computer will literally sit there until that one process finishes. The result: Your music stutters and FPS goes to hell.

In Linux and other OSs this problem was solved awhile ago. Even on my old T-Bird I could encode a movie at the default priority while listening to music and writing a text document with absolutely no problem. To do the same thing in Windows you need either Hypertheading or multiple processor cores.

Thanks for answering my question Eclipse. I suppose at this point Hyperthreading is somewhat irrellevant with multi-core processors on the horizon. But did I understand correctly that Intel has totally dropped Hyperthreading from future chip designs, was it really just a bandaid for the Pentium 4?
 
Hvatum said:
This is only a problem in windows because the damn Kernel isn't pre-emptible.

If a process is waiting for a response from a kernel level resource in Windows and that process has high priority everything else grinds to a hault until that process completes it's given task. The kernel will essentially give that process highest priority for what a long time even though it might not be doing anything but writing to the disk at the time. But since it's a kernel level operation (Disk IO) it can't be displaced by any user level process such as your MP3 player or video game. Your computer will literally sit there until that one process finishes. The result: Your music stutters and FPS goes to hell.

In Linux and other OSs this problem was solved awhile ago. Even on my old T-Bird I could encode a movie at the default priority while listening to music and writing a text document with absolutely no problem. To do the same thing in Windows you need either Hypertheading or multiple processor cores.

Thanks for answering my question Eclipse. I suppose at this point Hyperthreading is somewhat irrellevant with multi-core processors on the horizon. But did I understand correctly that Intel has totally dropped Hyperthreading from future chip designs, was it really just a bandaid for the Pentium 4?
Click to expand...


I hadn't heard Intel scrapped HT for new chips as they have dual core HT chips out. I had heard they'd scrapped netburst though frankly that is a tech I don't know anything about.
 
HighwayAssassins said:
well they could make their own...you cant patent a number of threads in a CPU...
Click to expand...


I hope you not trying to confuse peeps into believing hyperthread processors anywhere remotely resembles multithreaded processors.

Hyperthread != Multithread

Dual Core = Multithread
 
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