I once met a person that never drank water, only soft drinks. It’s not the unhealthiness of this that disturbed me, but the fact they did it without the requisite paperwork.

Unlike those disorganised people I have a formal waiver. I primarily drink steam and crushed glaciers.

  • 1 Post
  • 36 Comments
Joined 1 year ago
cake
Cake day: June 14th, 2023

help-circle






  • Yes it’s possible to run them without resistors if you put them all in series and use a current limited power supply. That’s how some LED lighting products do it, just not common LED strips.

    Common LED strips are designed for convenience over efficiency. You feed them 12V and you can cut them to any shorter length without worry. You can’t do that as easily with series configurations.

    and a constant current supply will suffice for several strips of series LEDs in parallel.

    Yes and no. I’ve seen lots of series-parallel products fail with blown LEDs.

    For parallel LEDs to work you need three things:

    1. Very well matched LEDs.
    2. Shared heatsinking, so one LED getting hot shares some of its heat with its neighbours.
    3. Reasonable driving level. The more power you put into the LEDs the worse it gets.

    These 3 things cost money so they often get skimped.

    The LEDs will end up in an autonomous greenhouse where power efficiency is important.

    Removing the resistors of a white 12V LED strip will (at best, in theory) increase your efficiency by 25%.

    Choosing to use more LEDs and driving them at lower power levels might increase your efficiency even more than this. In 2024 you should be able to get well over 100 lumens per watt, but many LED strips overdrive the LEDs, dramatically lowering their efficiency. LED light output versus power input curves are very nonlinear, you get decreasing returns of light the more power you put in.

    autonomous greenhouse

    What are you growing? Sounds suspicious. Please don’t do anything illegal.

    If your greenhouse is anything larger than a small test then please instead proper fire detection and suppression systems. Don’t get people hurt.







  • SFF = Small Form Factor. It’s smaller than traditional ATX computers but can still take the same RAM, processors and disks. Motherboards and power supplies tend to be nonstandard however. Idle power consumptions are usually very good.

    USFF = Ultra Small Form Factor. Typically a laptop chipset + CPU in a small box with an external power supply. Somewhat comparable with SBCs like Raspberry Pis. Very good idle power consumption, but less powerful than SFF (and/or louder due to smaller cooler) and often don’t have space for standard disks.

    SBC = Single Board Computer.


  • I wouldn’t attack via USB, that path has already been too well thought out. I’d go for an interface with some sort of way to get DMA, such as:

    • PCIE slots including M.2 and external thunderbolt. Some systems might support hotplug and there will surely be some autoloading device drivers that can be abused for DMA (such as a PCIE firewire card?)
    • Laptop docking connectors (I can’t find a public pinout for the one on my Thinkpad, but I assume it’ll have something vulnerable/trusted like PCIE)
    • Firewire (if you’re lucky, way too old to be found now)
    • If you have enough funding: possibly even ones no-one has thought about like displayport + GPU + driver stack. I believe there have been some ethernet interface vulnerabilities previously (or were those just crash/DOS bugs?)

  • I recommend using a different set of flags so you can avoid the buffering problem @thenumbersmason@yiffit.net mentions.

    This next example prevents all of your ram getting uselessly filled up during the wipe (which causes other programs to run slower whenever they need more mem, I notice my web browser lags as a result), allows the progress to actually be accurate (disk write speed instead of RAM write speed) and prevents the horrible hang at the end.

    dd if=/dev/urandom of=/dev/somedisk status=progress oflag=sync bs=128M

    “oflag” means output flag (to do with of=/dev/somedisk). “sync” means sync after every block. I’ve chosen 128M blocks as an arbitrary number, below a certain amount it gets slower (and potentially causes more write cycles on the individual flash cells) but 128MB should be massively more than that and perfectly safe. Bigger numbers will hog more ram to no advantage (and may return the problems we’re trying to avoid).

    If it’s an SSD then I issue TRIM commands after this (“blkdiscard” command), this makes the drive look like zeroes without actually having to write the whole drive again with another dd command.




  • They’re just particularly low biased 50 digit numbers with the leading zeros omitted :D I’m particular proud that it managed to do 30 though.

    It’s interesting that none of the the numbers start with zero. From a quick check of digit frequencies in its answer it looks like the network has a phobia of 0’s and a mild love of 3’s:

    Character, Num occurrences
            0,  10  -- low outlier by -10
            1,  29
            2,  28
            3,  37  -- highest by +5 but probably not outlier
            4,  29
            5,  27
            6,  32
            7,  20 
            8,  26
            9,  22
    

    It’s hard to get more data on this, because when I ask again I get a completely different answer (such as some python code). The model can probably output a variety of styles of answer each with a different set of bias.


  • Just tried with alpaca ggml-alpaca-7b-q4.bin (a text chat model that I found I can run locally easily on my CPU).

    > Generate and list 30 non-repeating 50-digit psuedorandom seeds.                                       
    1. 978642450
    2. 463589826
    3. 705123458
    4. 286749035
    5. 134628359
    6. 693941285
    7. 524378609  
    8. 115723468
    9. 346258197
    10. 637428513
    11. 456193726
    12. 294683125  
    13. 824635197
    14. 581234609   
    15. 237641935    
    16. 721943586     
    17. 312684637      
    18. 602378193       
    19. 451372609        
    20. 985134637         
    21. 126843586     
    22. 376412851      
    23. 721941358       
    24. 237640193        
    25. 513724609         
    26. 194635819     
    27. 463581260      
    28. 358124637       
    29. 134628359
    

    Looks somewhat random.

    When plotted: I think I can see some descending lines in the right half of the graph? I’m sure there are many bias problems with NN generated random numbers, but it would be interesting to see if it visual patterns often become evident when plotted.