With a 6600GT I doubt there is any video decoding going on in GPU so the CPU is doing 100% of the work. A fresh load may help since already saw issues or perhaps a newer video card or drivers?

AMD HD4xx0 and Nvidia Geforce 8x00 (not G80 but G84, G86 and G92 ) are the oldest cards that support Flash H264 video decoding today.
A 2.2 GHz single core S939 CPU can not handle Youtube full HD but should just manage 720P, a dual core will make 720P smoth as butter but 1080 is ... better to let the GPU handle it.

Windows 7 should run well though, not just OK. It should even feel snappy with 4GB memory.

Is it any better when you disable flash and use html5 video on youtube? I never struggled to play flash video on any of my current systems, but I noticed the cpu usage isn't as high as flash when I use html5 video.

Here's the HTPC system I was recently running, but I'm currently rebuilding:

ABIT KV85
Athlon 64 3400 Venice, socket 754
1GB RAM
XFX 7900GS AGP
ATI HDTV Wonder
Soundblaster Live! 5.1 Value (SB0220)
Running WinXP Pro SP3

In that configuration, I was able to do 720 pretty well, but 1080 was quite bad. 720 ran better with CoreAVC, but 1080 was still very bad. Fortunately, the TV I have it connected to is only a 720p model so it doesn't matter too much anyway.

I'm currently in the process of building a new image for this system. The only thing I've changed is the sound card; I have upgraded to an Audigy 2 ZS SB0350. I am not yet sure if the better sound card will have any impact on video playback performance.

According to this WikiPedia entry, NVIDIA has implemented PureVideo on models since the GF6 series. If you use VLC Player, it should take advantage of your card's hardware acceleration for video playback. However, with my 7900GS I didn't notice much difference between MPC-HC and VLC. They both played 720 adequately and 1080 poorly.

I'm quite interested to see what others have to say about YouTube performance in this thread. For a long time, I used to run a Radeon 9600XT in this same system and YouTube videos played fine. Sometime around 2012, something changed and they started to run like crap. This is actually what prompted me to upgrade to the 7900GS. However, now it too suffers poor performance with YouTube video.

So what exactly has changed and what is the solution? I intend to install the latest versions of Java, Flash, and Shockwave for my image. Maybe rolling them back post-imaging to versions from ~2011 will improve performance? Maybe running good ol' Firefox v3.6.28 will help? I'm not sure, but I can give it a shot and report back here later.

Maybe the cheapest/best solution for fixing this is to do as Skyscraper suggested and buy a Radeon 4350 or 4550. You can find 'em cheap on eBay. They do indeed support Flash H264 hardware accelerated decoding. They also compare to your 6600GT, so you shouldn't notice any decrease in gaming performance. Ideally, the Radeon 4670 is the much better choice but they're expensive, consume more power, and occupy two slots at a minimum. Your CPU will also likely be a bottleneck, so there's not much performance to gain by using the 4670. Since my ABIT KV85 is a micro-ATX board, I can't afford to sacrifice any of my PCI slots. Unfortunately for me, the 4670 is simply out of the question.

https://wiki.videolan.org/VLC_GPU_Decoding/

VLC hardware decoding requires geforce 8 or newer. The only way I could get 1080p videos to play with hardware acceleration on a 7800 was with Cyberlink PowerDVD.

Try disabling hyperthreading in the BIOS... or the equivalent if AMD uses a different name.

Try SMPlayer. It has a native YouTube support and plays HD videos just fine wth Athlon 64 3000+ Venice and GeForce 7600 GS.

KT7AGuy wrote:

According to this WikiPedia entry, NVIDIA has implemented PureVideo on models since the GF6 series.

Though note this https://en.wikipedia.org/wiki/GeForce_6_serie … GP_GeForce_6800
And AGP was still quite popular at this time.

Logistics wrote:

Try disabling hyperthreading in the BIOS... or the equivalent if AMD uses a different name.

AMD has no such thing (HyperThreading is an Intel-unique technology, and then only on certain processors). 😊

As far as GPU acceleration, the GeForce 6/7 have PureVideo, but do not support Flash accel (that requires GF8+ as has been mentioned). They can do partial h.264 or VC-1 h/w decode with a PureVideo compatible software player, although do not expect to see 0% CPU load like you would with a modern graphics card. See benchmarks for example:
http://hothardware.com/Reviews/NVIDIAs-GeForc … 7600-GT/?page=6
http://www.guru3d.com/articles-pages/inno3d-g … l-review,4.html
http://www.anandtech.com/show/2220/4 (includes a GeForce 8; notice the (original) 8800 doesn't fare well either, as it doesn't have the full PureVideo HD featureset)

But again, none of this will matter for YouTube - GeForce 7 does not support Flash accel. And it's worth pointing out - YouTube is not the same as conventional HD content, and shouldn't be lumped in with DVD/HD-DVD/Blu-ray/etc content as a result; crappy performance, support, etc is just par for the course (even with hardware that should support Flash accel, full h264, etc you can run into issues with things not working or being broken for a variety of reasons). In short, YouTube sucks. 🤣 😵

For Half-Saint:
As far as upgrading to a card that supports full h.264, Flash accel, etc, I would suggest the GeForce 8600 series (including the Quadro variant, the FX 1700) - they're generally pretty cheap, have full acceleration support, and nVidia only recently discontinued mainstream driver support (whereas AMD abandoned the Radeon HD 4000 series years ago). If you need more processing power (the 8600 will be faster than the 6600 by a fair margin; my FX 1700 (similar to the 8600GT) benchmarks similarly to my 7900GS in 3D01 and AQ3) the GeForce 9600 or another GeForce 9 card (including G92-based 8800s) would be a good consideration.

For KT7AGuy:
I wouldn't generally suggest the AGP bridged cards (especially ATi-based) due to potential compatibility issues, and reportedly they don't have HD decode enabled/supported (I've read varying claims, but the more common version seems to be that the AGP bridge cards (and native AGP cards, in the case of the 6800) will not have full decoding features enabled vs PCIe versions). Here's the nVidia list for AGP/PCIe comparison for decode: http://www.nvidia.com/docs/CP/11036/PureVideo … _Comparison.pdf (couldn't find one for ATi).

Half-Saint wrote:

720p video is relatively smooth with occasional hiccups while 1080p is worse. Is this normal? Am I expecting too much?

Same here i have a Socket 939 Venice Athlon 64 3200+ running at 2300 mhz ,2g ram and a Geforce 7600gs and i get same youtube experience.
Since i have agp,the best videocard with hardware flash acceleration would be an Ati 4670 but agp versions are hard to find and expensive,so best option is to get a Athlon 64 X2,but high end X2 cpu's for 939 are also a bit expensive.
Altough i would like to see if this proc,with a flash accelerated videocard will make 1080p on youtube fluent.

Just download the videos and play them from the hard drive in VLC, there are multiple addons that will download youtube videos in different formats and file sizes including normally locked material such as music videos ect.

Did a fresh install od Windows 7 Home Premium and performance is about the same. This motherboard supports PCI-E so I don't have to bother with AGP cards 😉

I have a BFG 8800GTS but it produces vertical dotted lines on the screen so it's probably toast.

Half-Saint wrote:

Did a fresh install od Windows 7 Home Premium and performance is about the same. This motherboard supports PCI-E so I don't have to bother with AGP cards 😉

I have a BFG 8800GTS but it produces vertical dotted lines on the screen so it's probably toast.

If it's a G80 card it also doesn't have the complete acceleration suite that the 8600 and G92 cards have (you would've thought nVidia learned after the 6800/6600 thing, but no, they didn't). Honestly, I'd just get an 8600 unless you need considerably more performance, in which case I'd get a G92-based card.

I think its because of crappy flash plugin.
A friend has AMD Athlon 64 3500+ and an nVidia GeForce 7600GT. When he moves the mouse the sound starts to chop and video lags 🤣