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macrumors newbie
Original poster
Jul 2, 2019
Hi everyone. Apologies in advance for the long wall of text. A couple of days ago I became the proud owner of an early 2008 20 inch iMac that I purchased for $38 USD ($50 Canadian). It has a 2.4 ghz Penryn Core 2 Duo, 4gb DRR2 800 mhz RAM, 250 gb 7200 rpm HDD, and a shockingly terrible Radeon HD 2400xt with 128 mb Vram. I am running El Capitan. All of the issues I describe where the same on Snow Leopard as they are on El Capitan. In fact, the system feels snappier on El Capitan.

Basically I bought this machine for the portability as it is a sleek looking and (now) cheap All In One PC that is relatively light and I can move from room to room and have a nice big screen and decent speakers in contrast to the the crummy Windows laptop I have. It is NOT meant to replace my primary PC (an i7 7700k/GTX 1070ti/32 gb RAM gaming beast). This iMac is not actually that bad for basics tasks like spreadsheets and light internet browsing, but by god Youtube 720p/1080p 60 fps video are extremely stuttery. In fact, the only smooth youtube videos I can play is 480p, even 720p 30 fps is still stuttery.

I notice when I play these videos a process in Activity Monitor called "VTDecoderXPCService" is taking up most of my CPU resources. It seems the HD 2400xt is not doing any video decoding and all is being off loaded to the CPU. Wikipedia mentions that the HD 2400 does not really support most formats of video decoding unless a registry hack is done, but that is in Windows, and this is a Mac.

"Several reports from owners of HD 2400 Pro suggest the card do not fully support hardware decoding for all H.264/VC-1 videos. The device driver, even with the latest stable version, seem to only honor hardware decoding for formats specified in the Blu-ray and HD-DVD specification. As a result of such restriction, the card is not deemed very useful for hardware video decoding since the majority of the H.264/VC-1 videos on the net are not encoded in those formats (even though the hardware itself is fully capable of doing such decoding work). This device driver restriction has led to the development of a third party driver patch, "ExDeus ATI HD Registry Tweak", to unlock the potential of HD 2400 Pro for full support of H.264/VC-1 hardware video decoding."

Is there a way to do it in OS X, or some otherway to make the HD 2400xt do some video decoding when watching Youtube so it doesn't completely bog down my CPU? No I am not willing to put more RAM in or do surgery to replace the HDD with an SSD, I doubt that would solve my issues anyway as I have a similar speced old Windows core 2 duo PC with a regular HDD and 4 gb RAM that can watch Youtube just fine (though it has an HD 5450...)
[doublepost=1562138858][/doublepost]And yes was originally clean installed Snow Leopard than updated to El Capitan (gives me an error when I try to edit my first post).


macrumors 68000
Sep 1, 2017
I've watched HD youtube videos on my early 2008 iMac without problem. In fact, I used it to watch the keynote in full screen last week and everything was buttery smooth.
Last edited:


macrumors Penryn
Feb 20, 2009
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