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Joined 1 year ago
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Cake day: July 5th, 2023

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  • An older friend of mine told me years back about an incident that happened on a university VAX running Unix. In those days, everyone was using vt100 terminals, and the disk drives weren’t all that quick. He was working on his own terminal when without warning, he got this error when trying to run a common command (e.g. ls)

    $ ls -l
    sh: ls: command not found
    

    So he went on over to the system admin’s office, where he found the sysadmin and his assistant, staring at their terminal in frozen horror. Their screen had something like:

    # rm -rf / tmp/*.log
    ^C^C^C^C^C^C^C^C^C^C
    # ls -l
    sh: ls: command not found
    # stat /bin/ls
    sh: stat: command not found
    

    A few seconds after hitting return, and the rm command not finishing immediately, he realised about the errant space, and then madly hammered Ctrl-C to try to stop it. It turns out that the disk was slow enough that not everything was lost, and by careful use of the commands that hadn’t been deleted, managed to copy the executables off another server without having to reinstall the OS.







  • I think 30fps (25fps in PAL-land) became the standard because televisions were 30 FPS (NTSC) or 25 FPS (PAL) due to interlacing. While the screen redraw on a NTSC television is 60 per second, it’s done as two fields so you only get 30 actual frames per second. This was done so you could have a decent resolution (525 lines for NTSC or 625 lines for PAL) while maintaining reasonable RF bandwidth limits for the TV signal by sending a single frame as two fields, half of the picture in each field on alternate TV scanlines.

    So you probably have a lot of industry inertia to deal with so 30 fps (or 25 fps where PAL was formerly the standard) ends up being the standard. And for video it’s good enough (although 60fps/50fps is still better - until fairly recently, this would entail too much bandwidth so sticking with the old NTSC or PAL frame rates made sense).

    But for computers no one really used interlaced displays because they are awful for displaying the kind of things computers usually show (the flicker is terrible with a static image in an interlaced screen mode. While it’s true there were some interlace modes, nearly everyone tried to avoid them. The resolution increase wasn’t worth the god-awful flicker). So you always had 60 Hz progressive scan on the old computer CRTs (or in the case of original VGA, IIRC it was 70 Hz). To avoid tearing, any animated content on a PC would use the vsync to stay synchronized with the CRT and this is easiest to do at the exact frequency of the CRT and provided very smooth animation, especially in fast moving scenes. Even the old 8-bit systems would run at 60 (NTSC) or 50 (PAL) FPS (although 1980s 8-bit systems were generally not doing full screen animation, usually it was just animating parts of the screen).

    So a game should always be able to hit at least 60 frames per second. If the computer or GPU is not powerful enough and the frame rate falls below 60 fps, the game can no longer use the vsync to stay synchronized with the monitor’s refresh, and you get judder and tearing.

    Virtual reality often demands more (I think the original Oculus Rift requires 90 fps) and has various tricks to ensure the video is always generated at 90 fps, and if the game can’t keep up, frames get interpolated (see “asynchronous space warp”) although if you’re using VR if you can’t hit the native frame rate, it’s generally awful having to rely on asynchronous space warp which inevitably ends up distorting some of the grpahics and adding some pretty ugly artifacts.






  • Renewables are already viable in the UK and making up an ever increasing percentage of electricity generation. Additionally, the time when it’s windiest in the UK is also the time when electricity demand is at its highest.

    Using coal for electricity in the UK is now rare. Coal only made up 1.5% of electricity generation in the UK in 2022. Just ten years ago coal generation was nearly half.




  • Twice, and they were completely different experiences.

    First was gas at the dentists for taking 3 teeth out as my mouth was overcrowded. I was kind of asleep, I could hear people’s voices in a really trippy flanged way, and I could vaguely feel some tugging at my jaw (but no pain). The gas tasted awful.

    The second was for an operation at hospital after an accident (requiring 6.5 hours of microsurgery). It was like jumping forwards 7 hours in time, literally counting the seconds after the anaesthetic went in at night, then immediately waking up in broad daylight. It is completely unlike deep sleep (where you still are aware that time has passed).