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How has 96 MHz helped you? — Parallax Forums

How has 96 MHz helped you?

cbmeekscbmeeks Posts: 634
in Propeller 1
As I mess around with CTRA/B and learning about timers, this leads me to learning about the system clock, PLL, etc.

In my research, I've seen a few people mention using a 6 MHz crystals to get 96 MHz.

So my question is, other than the obvious "more is better" speed, how have you benefited from the faster clock rate? Especially with video projects.

I'm more interested in projects you've worked on where the "slow" 80 MHz didn't quite cut it but when you went to 96 (or higher??) your project came to life.

Thanks!

Comments

  • Mark_TMark_T Posts: 1,981
    Well I've used 98.304MHz several times using a 6.144MHz crystal to support I2S audio
    at sample rates of 48kSPS or 96kSPS (I2S uses a clock thats typically 12.288MHz for
    these sample rates). This meant the code can run in lockstep with the ADC or DAC involved
    and feed in or retrieve bits in assembler. A couple of PLLs generate the master and bit clocks.
  • PublisonPublison Posts: 12,366
    I like the 6.25 Mhz xtals:
    https://www.parallax.com/product/251-06250

    Gets everything down to 10ns. (100Mhz)
  • Cluso99Cluso99 Posts: 18,069
    edited 2015-11-05 20:33
    I mostly use 6.5MHz (104MHz). This requires a specialised design with good decoupling and ground plane.

    I use it for my RamBlade (has 512KB of SRAM and a microSD) which can run huge C (Catalina) programs and also can run ZiCog (Z80 emulation) and CPM2.2

    My 1pin TV driver (composite B&W) runs wider screens (more character columns) as the clock is cranked up.

    If you are wanting to time something, you cannot beat the 6.25MHz (100MHz) provided the board is designed for it.
  • potatoheadpotatohead Posts: 10,261
    I second the timing point Cluso made. 6.25Mhz is just sweet for that.

    In my own projects, I've not really gained from over 80Mhz, and typically write for 80Mhz as a minimum. The extra speed can be handy, or improve quality, etc...

    Sometimes that extra speed can result in something only taking one COG. Depending on what the goal is, that might be very seriously worth it. I would probably rate that as a high value decision point. When it "almost fits" into a COG, looking at that speed difference possible is well worth your time, IMHO.

  • RaymanRayman Posts: 14,651
    I think 6 MHz was needed for people doing bit-banged USB drivers...

    There's some code out there that makes prop appear like a USB keyboard...
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