Comments by "Lawrence D’Oliveiro" (@lawrencedoliveiro9104) on "Why My Computer Wants to Forget (How Dynamic Memory Works) - Computerphile" video.

  1. 3:58 LEDs always need a resistor to stop them exploding, because they are prone to an effect known as “thermal runaway”. Most substances exhibit higher electrical resistance as their temperature rises. So as current flows through them and heats them up, this increases the resistance and acts as an automatic limit on how much more current can flow. LEDs exhibit the opposite behaviour: their resistance goes down as they heat up. Thus, if you put too much current through them, they heat up, lowering their resistance, and this means even more current flowing through, until they blow up, die etc.
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  2. I wonder why we don’t say at some point “OK, memory is now big enough, we can afford to go back to static RAMs now”. For example, you can easily pack in something like 64GiB of DRAM in a modern machine. If the same amount of circuitry can only amount to 16GiB of SRAM, that would still be very useful for many purposes. Also. SRAMs are faster to access, which is why they are used for high-speed caches. And think of the power saving!
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  3. You mean DRAM is like fine wine, and actually improves with age...?
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  4.  @elimalinsky7069  But SRAM uses less power, hence it puts out less heat.
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  5.  @elimalinsky7069  SRAM needs less complex controllers than DRAM. That’s part of the point.
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  6. Also there is this thing called “VRAM” (“Video RAM”). From the CPU side, it can be read and written like normal DRAM. But on the other side, there is a read-only port with a shift register that is continually transmitting the bits sequentially from memory. From there they are fed to video circuitry to interpret them as colour and brightness data etc before being output to a display. The point with this design is that the sequential output has low contention with regular CPU access, i.e. neither slows the other down much.
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  7. Yes, that can certainly happen. It’s called a “power glitch”. The usual cure is to unplug from the mains, wait 5-10 seconds, then plug it back in.
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  8.  @TomStorey96  That’s only if the POST can run.
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  9. 0:19 Norgate ... isn’t that in Sussex somewhere?
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  10.  @KuraIthys  But the price for SRAM is so high mainly because so little of it is manufactured. If it were more popular, the price would go down.
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  11.  @LittleRainGames  I’ve been thinking about this. “Conservatives” as supposed to be those who like to stick to how things were in the past. But they tend to exhibit very limited and selective memory of how things really were in the past. Those who actually study the history of how things were in the past, and try to learn from it, tend to get branded “Liberals”.
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  12. Leaving the device unplugged for 5-10 seconds isn’t just for the RAM, but for all the circuitry in the device to lose any stored charge. Unplugging and replugging the device too quickly can lead to glitches, where circuitry gets into a crazy state and the device locks up. This can happen during power brownouts, too.
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  13.  @TomStorey96  Memory tests have to be implemented by firmware/software, which cannot run properly if the hardware has glitched.
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  14.  @TomStorey96  Then you would know that leaving things unplugged is not a “carryover from a bygone era”.
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