This is a fascinating article. Footnote 8 is an especially fascinating insight;
> One puzzling feature of the shift register is that there is no wiring between the stages!
> How do bits get from one stage to the next? Did the chip have another layer of wiring that wasn't in
> the photos? Was there some sort of hidden connection? Eventually I noticed that there wasn't an isolation
> ring between the stages—a silicon barrier that separated most I2L circuits. Without this isolation ring,
> an "invisible" PNP transistor exists between the stages, apparently allowing one stage to flip the next
> stage to the right value. Each shift-register stage is constructed from two NAND-gate latches. When the
> clock is low, the first latch is forced into an indeterminate state. When the clock goes high, the latch
> ends up as 0 or 1 based on the bias it receives from the previous stage through the "invisible" PNP
> transistors. Thus, the latch becomes edge-sensitive since it will change right on the clock's rising edge.
> I found a paper ("Injection-Coupled Synchronous Logic", 1978) that describes a similar technique for an I2L
> shift register9, so I think this is the right explanation, even though the circuit seems a bit sketchy.
A direct link to the footnote, as the above is unreadable. (Hint: don’t use code formatting for quotes. It is semantically wrong and is unreadable on many devices.)
On HN, you can just "star" the paste at the beginning and end.
One puzzling feature of the shift register is that there is no wiring between the stages! How do bits get from one stage to the next? Did the chip have another layer of wiring that wasn't in the photos? Was there some sort of hidden connection? Eventually I noticed that there wasn't an isolation ring between the stages—a silicon barrier that separated most I2L circuits. Without this isolation ring, an "invisible" PNP transistor exists between the stages, apparently allowing one stage to flip the next stage to the right value. Each shift-register stage is constructed from two NAND-gate latches. When the clock is low, the first latch is forced into an indeterminate state. When the clock goes high, the latch ends up as 0 or 1 based on the bias it receives from the previous stage through the "invisible" PNP transistors. Thus, the latch becomes edge-sensitive since it will change right on the clock's rising edge. I found a paper ("Injection-Coupled Synchronous Logic", 1978) that describes a similar technique for an I2L shift register9, so I think this is the right explanation, even though the circuit seems a bit sketchy.
Semantically wrong or not, it's all the HN developers have chosen to give us for blockquoting. That's not the users' fault.
For mobile, it helps if you manually truncate lines, like so:
One puzzling feature of the shift register
is that there is no wiring between the stages!
How do bits get from one stage to the next?
Did the chip have another layer of wiring that
wasn't in the photos? Was there some sort of
hidden connection? Eventually I noticed that
there wasn't an isolation ring between the
stages—a silicon barrier that separated most
I2L circuits. Without this isolation ring,
an "invisible" PNP transistor exists between
The site is called "Hacker News," after all. Apparently that's because we're expected to, well, hack.
> For mobile, it helps if you manually truncate lines, like so
Mobile user here, your manual truncation was not enough unfortunately; it still gets cut off.
Leading white space is for code.
I wish everyone stopped making “blockquotes” with leading whitespace. It makes the text hard to read on mobile and it looks strange to have it in monospace font anyway.
Instead, prefix each paragraph of quoted text with the “>” but no leading whitespace and it’s clearly visible that you are quoting.
> One puzzling feature of the shift register is that there is no wiring between the stages! How do bits get from one stage to the next? Did the chip have another layer of wiring that wasn't in the photos? Was there some sort of hidden connection?
> Eventually I noticed that there wasn't an isolation ring between the stages—a silicon barrier that separated most I2L circuits.
> Without this isolation ring, an "invisible" PNP transistor exists between the stages, apparently allowing one stage to flip the next stage to the right value.
> Each shift-register stage is constructed from two NAND-gate latches. When the clock is low, the first latch is forced into an indeterminate state. When the clock goes high, the latch ends up as 0 or 1 based on the bias it receives from the previous stage through the "invisible" PNP transistors.
> Thus, the latch becomes edge-sensitive since it will change right on the clock's rising edge. I found a paper ("Injection-Coupled Synchronous Logic", 1978) that describes a similar technique for an I2L shift register9, so I think this is the right explanation, even though the circuit seems a bit sketchy.
They are not just programmers, they also moderate and put the trash out and have a life besides. Try being a bit more considerate of people whose lives you have no idea about and that work hard to make your life easier.
Well, if you want your posts readable there seem to be two choices - either convince HN to change their code or use what they support. Which one do you think is more likely to happen?
I don't care either way, since I rarely read HN on mobile. But I sympathize with people who do, which is why I manually break quoted lines at a few dozen characters. Does anyone have a problem reading my example above?
(Granted, it's at -3 and falling, so the text color will be the biggest challenge for mobile users. They can't highlight grayed-out text as easily. About the only safe conclusion I can draw, from the outside looking in, is that HN doesn't like mobile users very much.)
As far as I can tell, formatdoc[0] doesn't provide a "semantically correct" method for formatting quotes. Hence, the age-old usenet quote (as codified in RFC3676[1]) seems to me to be the best way of indicating a quotation, and rendering it via a verbatim block ensures that the line-based quotation indication isn't disrupted by the text all being in a <p> tag when rendered in HTML.
Even on my desktop, unless I shrink the text down to a size that's too small for me to read, it's displayed as a horizontally scrolling block. (Using Firefox.)
I definitely bought this chip and a bunch of pots and caps and twiddled with it. While I had a full sized Yamaha organ at home to make music with, being able to invent my own sounds was almost more satisfying. I'm definitely more an engineer than an artist, but continually struggle to keep focused on bringing projects to conclusion as they interfere with each other.
Last year's article described the analog parts of the sound chip
The new article discusses the digital circuits and how they are implemented using I2L logic, a competitor to TTL.
This reminded me I have two of this chip sitting in my parts bin, with nice little DIP format adapter boards even. It bugs me that I bought the chips ~18 years ago and still haven't done anything with them. My project queue needs some reshuffling. I should start making synth modules again.
Or I should find myself a Blacet Dark Star Chaos module. I should have bought one when I had the chance.
Lol, I have a couple lying around I had earmarked for building a midi interface for. Maybe my 8-y/o daughter will 'grow into them' as she is the only person in the house with any ability to play keyboards.
Brought back great memories. In the early 80s, I used this chip to build a small analog synthesizer. My dream was to build an Elektor Formant but had to settle for the 76477. But I learned a lot from that exercise
Wow. I didn't realize that an analog synthesizer-in-a-chip was a thing that far back. Pretty remarkable. All the basics are there: oscillator, noise generator, filter, envelopes, lfo.
Although it's not quite everything. The VCF is for noise only, and there's no way to insert a filter into the VCO audio path externally. However, that pretty much defines the "chip tune" genre.
