520 MHz versus 520 MHz

Discussion in 'Palm' started by grantorinosport, Feb 25, 2010.

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  1. grantorinosport

    grantorinosport Mobile Evangelist

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    As mentioned in a previous post, I use the following WarpSpeed settings:

    BUS 13 x 20 = 260 MHz
    CPU:BUS x 4 / 2 = 520 MHz

    In other words I bump up the CPU one notch and the Bus up 4 notches.

    Raspabalsa - you had questioned (rightfully so) the difference or necessity to set the bus speed up versus just simply running the CPU speed up two notches (to 520 MHz).

    I thought about it, and so I decided to instead only bump the CPU speed up (leaving bus speed at factory norm):

    In WarpSpeed I use the following settings:

    BUS 13 x 16 = 208 MHz
    CPU:BUS x 5 / 2 = 520 MHz

    Using those settings for a few days I noticed quite a bit of instability. I guess the most blaring problem was in PTunes. When I go to bed I will often have the TX play soft music for like 90 minutes or so. During the period when I was using these new settings, I noticed PTunes freezing up - sort of like when an Intellivision or Commodore 64 would freeze up, and the last note of sound would keep playing. It was kind of creepy waking up at 3AM to some awful noise and it was the TX frozen.

    So I guess on some TX's it does make a difference. At least from the standpoint of how fast the TX CPU can go before instability sets in. I know there are TX's out there that can handle a CPU speed of 600+MHz.

    I have a spare TX. I will get WarpSpeed installed on that and see how it performs. (something I was meaning to do, anyway).

    I guess it would also be interesting to try and perform some sort of calibrated speed tests. Something like watching a h.264 movie on CorePlayer and working with large PDF files. I'll try and play around with that this weekend.
     
  2. raspabalsa

    raspabalsa Brain stuck BogoMipping

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    Well, thanks yo our earlier exchange, and based on Dmitry's statement that it was safe to bump up the bus, I decided to change my settings. I no longer run my TX's bus at 13x16 = 208MHz. I decided to increase it to 13x20 = 260MHz.

    I've been doing this for several weeks, and so far my TX is as stable as always. Not a single crash, white screen of death, or Commodore-like howls :D

    I use my TX a lot, especially to watch movies with CorePlayer. On my last trip I watched about 6 hours of movies (MP4s with 600kbps H.264 video) with my TX overclocked to 520MHz (bus at 260MHz, CPUx4/2 = 520 MHz). But I'm not sure if battery endurance is affected by this. I'm not able to tell if my TX's battery lasts more, the same, or less. Same with performance: movies play just as well as with the TX overclocked to 520MHz with the 208MHz bus. I think I should run CorePlayer's benchmark to see if performance is affected. Give me a couple of days and I'll tell you what I find.
    I've read that this is true. Some TXs can be bricked if overclocked too far, especially the "flash" TXs. A friend just got one of these rare TXs and he's angry because he can't watch high bitrate h.264 videos on his machine because he doesn't dare to overclock and possibly brick it.
    CorePlayer has a benchmark tool. Get a fast action movie clip (a combat scene out of 300, Alexander, or The Lord of the Rings) and run the benchmark, see what maximum framerate you can get when varying the clock.
     
  3. raspabalsa

    raspabalsa Brain stuck BogoMipping

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    I finally ran some tests with CorePlayer varying the bus speed. I ran two sets of tests with the following Warpspeed settings:

    1: Bus 13x16 = 208MHz CPU Bus x 5/2 = 520MHz (208Mhz is the default Bus clock for the TX)

    2: Bus 13x20 = 260MHz CPU Bus x 4/2 = 520MHz

    For both sets I used the same video clip, a fragment of the Battle of Gaugamela from the movie "Alexander". This clip is encoded in an MP4 container with H.264 video at 600kbps, AAC audio at 128Kbps, 23.976 fps, 480x208 frame dimensions.

    I ran the same videoclip 3 times for every set. Using CorePlayer's benchmark tool the set with the higher Bus (260MHz) performed noticeably better. Benchmark scores 129% average, with a maximum framerate of around 30.9fps. When using the lower Bus (208MHz), the benchmark dropped to around 115.5% average, with maximum framerate of 27.8fps.

    I think this shows that increasing the Bus speed will increase overall performance for the same final CPU speed. Surely because the memory and peripherals are running at a higher Bus. I think I didn't notice any difference in playback earlier because at both Bus speeds my TX is able to cope with my videos (both benchmarks scored above 100%). Although the benchmark difference is relatively low (10% for a Bus speed increase of 25%), it still means you can play higher bitrate videos if you increase the Bus.
     
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