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generuso

527 karma · joined January 26, 2021

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generuso··on Lost Images from the 1945 Trinity Nuclear Test Restored
It is all true, but one needs to take into account that because of the different properties of the materials, the critical mass for uranium-235 is intrinsically much greater than that for plutonium-239.

For a bare sphere, it is about 10 kg for plutonium and 50 kg for uranium.

generuso··on How diamonds are made
99% of all diamonds by mass are industrial diamonds. But they are so inexpensive that they only account for 3% or the revenue.

The jewelry is the remaining 0.8% by mass, and it is split roughly equally between the natural and synthetic stones by mass, but with about 80% of the revenue going to the natural stones.

Here is a very good video showing how large poly-crystalline industrial diamonds are made in the USA: https://www.youtube.com/watch?v=6o5RprIJmfA

China has their own, slightly different flavor of this machine, the cubic press. These machines are manufactured in thousands and cost about half a million USD each. They are used to produce both industrial and jewelry quality diamonds: https://www.youtube.com/shorts/cED0TjwKUDM https://www.youtube.com/watch?v=5cnEVb7aPfM

The original machine was invented by a guy at General Electric: https://en.wikipedia.org/wiki/Tracy_Hall

generuso··on I'm scared about biological computing
I think one can extrapolate further. There will be two things intertwined together:

1. Thought will be liberated from the confines of mortal bodies. 2. Technology will be able to create and modify things on the molecular level, limited only by imagination (and the laws of physics of course).

Spirits will be roaming the cloud, developing in ways unseen before, and interfacing with the "real process" through whatever shapes suit the purpose.

Of course, learning from the treasure of design solution accumulated through the billions of years of biological evolution will be a large step towards this. Extending this heritage will be the next step.

generuso··on Gallium oxide electronics withstand extreme cold
The point is not that silicon is not suitable for extreme cold -- it is, with careful design. But the authors want to use a semiconductor which would operate at much higher temperatures than silicon can. And most of these have a disadvantage that they stop working at low temperatures.

What the authors have developed, is transistors which could work at a very high temperature, but also work at extremely low temperature. That is quite rare.

generuso··on Gallium oxide electronics withstand extreme cold
Exactly. In physics, when people measured things at 4K, there were many examples of active circuits built to measure or amplify things in situ at 4K, and only send the results out, often by the same wire that was used to power the circuit.
generuso··on Making RAM at Home [video]
It was unintentional, but it is actually kind of true in his case. The guy is a founder and the CTO of two semiconductor companies.
generuso··on Making RAM at Home [video]
In the "real" DRAM chip, there is a large array of very tiny capacitors, with the switches which allow to connect one row of the array at a time to the readout column wires.

The capacitance of the wires themselves is typically an order of magnitude greater than that of the storage capacitors. So when the memory is read, the wires are first precharged to some standard voltage. Then the desired row of storage capacitors is connected to the wires, and the charges from the storage capacitors spread onto the wires, changing their voltages very slightly. These voltage deviations from the standard value are amplified by the "sense amplifiers". The amplifiers are sort of like flip-flops. Once they start in a state which "tilts" slightly to "zero" or slightly to "one", they go all the way to the full magnitude zeros and ones. This not only amplifies the signal, but also automatically brings the voltages on the wires and the still connected to them capacitors to the full magnitude, thus "refreshing" the data. The row is disconnected, and the next read cycle can start for some other row.

In the video, an array of 4x5 capacitors and the associated with them switches was fabricated. The capacitors in the video are several hundred times larger (12400 fF) than typical capacitors in a 64 Kbit DRAM (about 50 fF). I assume this is done so that in the later episodes the author could implement the readout electronics outside of the chip.

generuso··on Making RAM at Home [video]
It is not really feasible to fabricate usable integrated circuits at home. There is a huge difference between a one off demonstration of a principle that "sort of works", and perfecting the process to the point that it produces finished parts that can be relied on.

This guy is not exactly a regular person. He is a pretty unique case of a talented semiconductor engineer who has a home lab for side hassles. It is not a low effort thing. He runs the equipment 24/7, scrubs all the surfaces in the lab daily to keep it clean.

Still, with the lab and all of the equipment already at hand, it cost him several weeks of work to produce this demonstration of transistors and capacitors, which kind of work, but are still long ways from a "completely complete" 20 bit DRAM chip.

Unfortunately it is simply too much work for one person to maintain a viable semiconductor fabrication process, even when it is done semi-professionally.

generuso··on Making RAM at Home [video]
Of course it not easy. He spent $20k on materials and a good amount of elbow grease just to construct this one room. In order to maintain the clean environment the air circulation runs 24/7 and he washes all the surfaces daily using cleanroom wipes. Deionized water system provides water for washing the cleanroom gowns. It is a lot of work just to have a small facility at home for odd jobs.
generuso··on Making RAM at Home [video]
The furnace is a low cost off-the-shelf Chinese product from Anhui Beq Equipment Technology Co.

Much more impressive are the modifications to the microscope, transforming it into an improvised lithography machine, and the home made plasma etching machine, cobbled together from surplus components.

Of course, the whole thing, starting from the clean room, is extremely impressive -- Intel started their business in a much simpler facility.

generuso··on Helium is hard to replace
Pure hydrogen in a balloon produces a low, loud, very satisfying bang. Completely different from a sound of an air balloon popping. Here is a video from a very good Royal Society of Chemistry demonstration series on various unusual combustion process:

https://www.youtube.com/watch?v=Rwbyl7ywfhk&list=PLLnAFJxOjz...

Hydrogen mixed with air or with oxygen produces an ear piercing supersonic detonation, exceedingly loud and unpleasant. Not recommended for demonstrations.

generuso··on Helium is hard to replace
There are many cases in the news of accidents with sometimes a large number of party balloons filled with hydrogen or other flammable gases.

One of the larger episodes was in 2012 in Armenia, where thousands of balloons exploded during a meeting, injuring 154 people, of which 4 seriously (the video is of poor quality): https://www.youtube.com/watch?v=jWEm2sS7Dw8

A smaller, more recent episode in India: https://www.youtube.com/watch?v=FH5JwHeKnZo

generuso··on Starlink militarization and its impact on global strategic stability (2023)
Starlink project began after Musk and Greg Wyler parted their ways. Wyler approached SpaceX in 2014 with a proposal to build OneWeb (then called WorldVu), and initially they worked on the project together. But then they started to accuse each other of doing various underhanded things, and split. After that, Musk decided that he could do a similar and even better system without Wyler, and that's how Starlink was born in 2015.
generuso··on Qatar helium shutdown puts chip supply chain on a two-week clock
Heat capacity is irrelevant -- argon and helium have exactly the same heat capacity per liter of gas, which would be the figure of merit in this context.

Heat conductivity, on the other hand, is an order of magnitude higher for helium, compared to argon, because its atoms are moving faster due to their lower mass.

When the gas is used for cooling, heat conductivity is important because it determines the conductivity through the boundary layer near surface, where the velocity of the flow drops to zero at the surface itself, and all the heat transport is through conduction rather than advection.

generuso··on Lidar waveforms are worth 40x128x33 words
Sure. Line scan indoor units are extremely affordable, and some cost less that $20, sold as spare parts for robot vacuum cleaners. Outdoor units (with higher ambient light tolerance and longer range) are an order of magnitude more expensive, but also available.

Here is some detailed information about low cost units: https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...

generuso··on ASML unveils EUV light source advance that could yield 50% more chips by 2030
The efficiency of X-ray tubes is proportional to voltage, and is about 1% at 100kV voltage. This is the ballpark for the garden variety Xray machines. But the wavelength of interest for lithography corresponds to the voltage of only about 100V, so the efficiency would be 10 parts per million.

The source in the ASML machine produces something like 300-500W of light. With an Xray tube this would then require an electron beam with 50 MW of power. When focused into a microscopic dot on the target this would not work for any duration of time. Even if it did, the cooling and getting rid of unwanted wavelengths would have been very difficult.

A light bulb does not work because it is not hot enough. I suppose some kind of RF driven plasma could be hot enough, but considering that the source needs to be microscopic in size for focusing reasons, it is not clear how one could focus the RF energy on it without also ruining the hardware.

So, they use a microscopic plasma discharge which is heated by the focused laser. It "only" requires a few hundred kilowatts of electricity to power and cool the source itself.

generuso··on Sub-$200 Lidar could reshuffle auto sensor economics
Neato from San Diego has developed a $30 (indoor, parallax based) LIDAR about 20 years ago, for their vacuum cleaners [1].

Later, improved units based on the same principle became ubiquitous in Chinese robot vacuums [2]. Such LIDARs, and similarly looking more conventional time-of-flight units are sold for anywhere between $20-$200, depending on the details of the design.

[1] https://scholar.google.com/scholar?q=%22A+Low-Cost+Laser+Dis... [2] https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...

generuso··on How Taalas “prints” LLM onto a chip?
You could [1], but it is not very cheap -- the 32GB development board with the FPGA used in the article used to cost about $16K.

[1] https://arxiv.org/abs/2401.03868

generuso··on How Taalas “prints” LLM onto a chip?
LSI Logic and VLSI Systems used to do such things in 1980s -- they produced a quantity of "universal" base chips, and then relatively inexpensively and quickly customized them for different uses and customers, by adding a few interconnect layers on top. Like hardwired FPGAs. Such semi-custom ASICs were much less expensive than full custom designs, and one could order them in relatively small lots.

Taalas of course builds base chips that are already closely tailored for a particular type of models. They aim to generate the final chips with the model weights baked into ROMs in two months after the weights become available. They hope that the hardware will be profitable for at least some customers, even if the model is only good enough for a year. Assuming they do get superior speed and energy efficiency, this may be a good idea.

generuso··on How Taalas “prints” LLM onto a chip?
The document referenced in the blog does not say anything about the single transistor multiply.

However, [1] provides the following description: "Taalas’ density is also helped by an innovation which stores a 4-bit model parameter and does multiplication on a single transistor, Bajic said (he declined to give further details but confirmed that compute is still fully digital)."

[1] https://www.eetimes.com/taalas-specializes-to-extremes-for-e...

generuso··on Japan's gamble to turn island of Hokkaido into global chip hub
It is not the same kind of equipment. ASML machines use a 500 watt EUV source in order to be able to expose a few wafers per minute. The tabletop device has the output power listed as "1 uw-10 mw". This is a source intended of spectroscopy instrumentation, not for exposing wafers.
generuso··on Blue Origin lands New Glenn rocket booster on second try
One of their patents describes exactly that -- driving a hardened stud into the softer metal of the deck, essentially by using a gunpowder actuated nail gun:

https://patents.google.com/patent/US20240092508A1/en

They have also included a way to disconnect the stud from the leg afterwards, such that the deck can be tidied up conveniently after the rocket had been removed. This is a neat idea -- the damage to the deck should very localized, and the rocket gets secured quickly and without putting human welders at risk.

generuso··on New analog chip capable of outperforming top-end GPUs by as much as 1000x
The idea was always appealing, but the implementation has always remained challenging.

For over a decade, "Mythic AI" was making accelerator chips with analog multipliers based on research by Laura Fick and coworkers. They raised $165M and produced actual hardware, but at the end of 2022 have almost gone bankrupt and since then there has been very little heard from them.

Much earlier, the legendary chip designers Federico Faggin and Carver Mead founded Synaptics with an idea to make neuromorphic chips which would be fast and power efficient by harnessing analog computation. Carver Mead published a book on that in 1989: "Analog VLSI and Neural Systems", but making working chips turned to be too hard, and Synaptics successfully pivoted to touchpads and later many other types of hardware.

Of course, the concept can be traced to an even older and still more legendary Frank Rosenblatt's "Perceptron" -- the original machine learning system from 1950s. It implemented the weights of the neural network as variable resistors that were adjusted by little motors during training. Multiplication was simply input voltage times conductivity of the resistor producing the current -- which is what all the newer system are also trying to use.

generuso··on Power over Ethernet (PoE) basics and beyond
From what I have seen, Ethernet ports always have a small isolation transformer for each twisted pair, between the connector and the PHY. Usually four of such transformers are combined in one small magnetics package. The insulation in the transformer is specified to withstand over a kilovolt of lightning induced voltage -- that's one of the purposes of such galvanic isolation.

The data travels as the differential voltage in each of the twisted pairs, and is transmitted magnetically by the transformer to the secondary winding. The power is applied between different pairs, and in each pair appears as a common mode voltage. This is all stopped by the transformer, and in devices designed to support PoE, the PoE circuits tap the mid-point of the primary windings to access the supplied voltage.

So at a first glance, it seems that if 48 volts is applied between the twisted pairs to a non-PoE device, this voltage would simply be blocked by the transformer. But since there is a widespread concern about this, there must be more to the story -- maybe somebody who actually worked with these circuits can explain why this is more complicated than it seems at first?

Edit: Found an answer. It seems that at least some of the designs of non-PoE Ethernet jacks terminate the common mode signals to a common ground though 75 Ohm resistors. In this case, if the voltage were applied between the twisted pairs, the resistors would dissipate far too much power and would burn out. So there is definitely a concern with the dumb PoE injectors and at least some non-PoE devices. https://electronics.stackexchange.com/questions/459169/how-c...

generuso··on Minds, brains, and programs (1980) [pdf]
It all started with ELIZA. Although Weizenbaum, the author of the chatbot, always emphasized that the program was performing a rather simple manipulation of the input, mostly based on pattern matching and rephrasing, popular press completely overhyped the capabilities of the program, with some serious articles debating whether it would be a good substitute for psychiatrists, etc.

So, many people, including Searle, wanted to push back on reading too much into what the program was doing. This was a completely justified reaction -- ELIZA simply lacked the complexity which is presumably required to implement anything resembling flexible understanding of conversation.

That was the setting. In his original (in)famous article, Searle started with a great question, which went something like: "What is required for a machine to understand anything?"

Unfortunately, instead of trying to sketch out what might be required for understanding, and what kinds of machines would have such facilities (which of course is very hard even now), he went into dazzling the readers with a "shocking" but a rather irrelevant story. This is how stage magicians operate -- they distract a member of the audience with some glaring nonsense, while stuffing their pockets with pigeons and handkerchiefs. That is what Searle did in his article -- "if a Turing Machine were implemented by a living person, the person would not understand a bit of the program that they were running! Oh my God! So shocking!" And yet this distracted just about everyone from the original question. Even now philosophers have two hundred different types of answers to Searle's article!

Although one could and should have explained that ELIZA could not "think" or "understand" -- which was Searle's original motivation, this of course doesn't imply any kind of fundamental principle that no machine could ever think or understand -- after all, many people agree that biological brains are extremely complex, but nevertheless governed by the ordinary physics "machines".

Searle himself was rather evasive regarding what exactly he wanted to say in this regard -- from what I understand, his position has evolved considerably over the years in response to criticism, but he avoided stating this clearly. In later years he was willing to admit that brains were machines, and that such machines could think and understand, but somehow he still believed that man-made computers could never implement a virtual brain.

generuso··on Neural audio codecs: how to get audio into LLMs
One of the popular speech-to-text models is Whisper, which starts with the conventional spectral analysis of the speech signal, and then feeds the data into a Transformer model. It works quite well.

https://openai.com/index/whisper/

Such approach dates back to 1940s, when people were trained to read the speech from spectrograms. There is a 1947 book "Visible Speech" by Potter, Kopp, and Green describing these experiments. Here is a more slightly recent 1988 review of the subject: "Formalizing Knowledge Used in Spectrogram Reading"

https://apps.dtic.mil/sti/tr/pdf/ADA206826.pdf

generuso··on A laser pointer at 2B FPS [video]
Mainstream oscilloscopes typically have sampling frequency at least five times greater than the bandwidth of the analog front-end. For example 1 GHz bandwidth oscilloscope will have sample rate of 5 GSps.

https://www.tek.com/en/products/oscilloscopes https://www.keysight.com/us/en/catalog/key-34771/infiniivisi...

"Sampling" oscilloscopes are a much less common product -- they are useful for analyzing signals that are too fast to digitize in the ordinary way. They typically sample at a very slow repetition rate -- some hundreds of kilohertz, but each sampling aperture can be exceptionally short, allowing to record signals to 100 GHz frequency.

generuso··on A laser pointer at 2B FPS [video]
Quite right. There are many different kinds of depth sensors in addition to the canonical old school rotating mirror LIDAR.

I think some of the short range depth cameras (Kinect v2 was one) use time-of-flight technique, and could in principle be reconfigured to perform a similar demonstration, though it would not be as "homemade" and cool as the system built for the Youtube video.

generuso··on A laser pointer at 2B FPS [video]
Yes, the laser was fired at 3 KHz, while the mirrors were slowly scanning across the room.

For each laser pulse, one microsecond of the received signal was digitized with the sample rate of 2 billion samples per second, producing a vector of light intensity indexed by time.

A large number of vectors were stored, each tagged by the pixel XY coordinates which were read out from the mirror position encoders. In post-processing, this accumulated 3D block of numbers was sliced time-wise into 2D frames, making the sequence of frames for the clip.

generuso··on A laser pointer at 2B FPS [video]
What this experiment does is very similar to how an ordinary LIDAR unit operates, except that during a LIDAR scan the laser and the receiver are always pointed in the same direction, while in this demonstration the detector is scanning the room while the laser is stationary and is firing across the room.

But in principle, a LIDAR could be reconfigured for the purposes of such demonstration.

If one wants to build the circuit from scratch, then specifically for such applications there exist very inexpensive time-to-digital converter chips. For example, Texas Instruments TDC7200 costs just a few dollars and has time uncertainty of some tens of picoseconds.

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