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by reerdna 1203 days ago
Using the FPU I believe but quite inefficiently, most cycles are probably spent in integer operations and chasing linked lists for the lisp parser. http://forum.ulisp.com/t/barnsley-fern-in-ulisp/1087

48MHz is the most power efficient mode, you can run it at 96Mhz "burst mode" but apparently it uses disproportionately more power, I have not measured how much.
1 comments
kragen 1203 days ago
It's really exciting to see this stuff coming to life!

Does this display have the same nominal 2Mbps speed as the 2.7" one I've been using? I've seen people report that it works well at 6Mbps (and thus 60 Hz) but haven't tried it myself. I'm guessing that it would use more power.

Have you been able to measure how much of the power consumption is the display?

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reerdna 1203 days ago
Yes, I'm running the display SPI at 2MHz which is ~25 fps. Overclocking it to twice as fast works just fine but uses significantly more power as expected. I did not try to go further.

Approximately 25%-50% of the total power depending on refresh rate. Worst case seems to be alternating black and white pixels, maximizing the number of transitions?

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kragen 1203 days ago
I haven't measured, but the way the power consumption numbers are written in the datasheet (for the 2.7" one) does imply that alternating black and white pixels like that is the worst case.

So the display is about 25% of the 4.9 mW number? That's exciting! How often are you toggling the polarity of the LCD field? I've noticed that when I unplug the display it continues to display the same data for about 30 seconds on what is presumably the screen capacitance, but the datasheet minimum clock for that is IIRC 10 Hz, and as I understand it, never switching the polarity will eventually destroy the liquid crystals.

One of the things I really hate about normal computers is how high the interaction latency is, and one of the really appealing things about these displays to me is the possibility of getting much lower interaction latencies using partial screen updates, down in the submillisecond range (plus 10–20 ms for the crystals to fully change state, but it should be visible before that).

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kragen 1203 days ago
Oh, responding to your email, I got this bounce:

    This is the mail system at host adjuvant.canonical.org.

    I'm sorry to have to inform you that your message could not
    be delivered to one or more recipients. It's attached below.

    For further assistance, please send mail to postmaster.

    If you do so, please include this problem report. You can
    delete your own text from the attached returned message.

                   The mail system

    <(your email address)>: host mx01.mail.icloud.com[17.42.251.62] said: 554
        5.7.1 [HM08] Message rejected due to local policy. Please visit
        https://support.apple.com/en-us/HT204137 (in reply to end of DATA command)
I removed your email address from this comment in case it gets harvested by spambots.
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