
Looking inside a vintage Soviet TTL logic integrated circuit - sohkamyung
http://www.righto.com/2020/03/looking-inside-vintage-soviet-ttl-logic.html
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eebynight
I love posts like these. For more of this stuff I recommend checking out
ZeptoBars.

[https://zeptobars.com/en/](https://zeptobars.com/en/)

Lots of die shots and I’m always blown away by the beauty of some chips when
designers fully know it is unlikely their art will see the light of day.

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jcims
Very cool. Second die down is a pretty neat UWB transceiver that is build for
real-time location services using multiple strategies (TDoA, ToF, etc). Looks
like a little of that rf black magic on the right.

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Gibbon1
The blue highlighted circular structures I believe are rf inductors.

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strategarius
Old Russian joke: "Soviet microchips are largest microchips in the world!"

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tdsamardzhiev
"This year a semiconductor factory, next year a whole-conductor factory!"

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lb1lf
-Are part-time band leaders semi-conductors?

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IndrekR
The joke is more to the point than one may expect:
[https://en.wikipedia.org/wiki/Valence_and_conduction_bands](https://en.wikipedia.org/wiki/Valence_and_conduction_bands)

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dfox
As for foot note 3: I suspect that reasoning for mostly not using TTL inverter
chips in eastern designs was limiting number of BOM entries and number of chip
designs that have to be manufactured in large volumes. Another thing is that
in many designs the author just used random NPN transistor (selected on the
basis of availability, so seeing RF power transistors used for almost anything
was not that uncommon) and resistor.

Edit: and to me, 134ЛА8 with it's connected inputs seems to be explicitly
designed to be usable as either bus driver or invertor replacement. You would
not want to use that in hand-optimized random combinatorial logic.

Edit2: on the other hand I would not be too surprised if there was IBM SLT
module that implements half of or even whole 134ЛА8 :)

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basementcat
The Smithsonian has a microchip collection! I had the good fortune to see the
physical exhibit when it was at the Museum of American History.

[http://smithsonianchips.si.edu/](http://smithsonianchips.si.edu/)

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bogomipz
I had a general question that came to mind when looking at the "How a TTL NAND
gate works" section and the accompanying schematic. Are the INs and OUT lines
in chips like MOSFETs implemented via the metal layers of the integrated
circuits?

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kens
I'm not sure exactly what you're asking. The chip's inputs and outputs are
wired from the chip's pins to metal pads on the die. These signals then routed
(mostly) through various metal layers to the transistors. For a MOSFET, the
source and drain are in the silicon, while the gate is a polysilicon layer
over top. The source, gate, and drain usually have contacts connecting them to
the metal layer.

I wrote a post explaining how some of the MOSFETs in the Z-80 microprocessor
are wired up. It might help you:
[http://www.righto.com/2013/09/understanding-z-80-processor-o...](http://www.righto.com/2013/09/understanding-z-80-processor-
one-gate.html)

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bogomipz
Wow, this post is really amazing!Thanks! I had a couple of question about the
following:

>"If input A is high, the first transistor will conduct and connect the yellow
strip to ground (dotted line 1)"

How does A being high connect the yellow to ground exactly if it doesn't cross
the yellow strip? I'm not understanding what the dotted line represent I
guess.

>"On the left, the yellow metal line ties together parts of the gate. In the
middle is the blue ground line, which is critical to the operation of the
gate."

Is the yellow metal line much much shorter than all the other vertical lines
then? The other vertical lines seem to be longer in the pic. Why does input
line "A" not cross the yellow metal line but the other 3 do?

What is the actual function of the yellow vertical strip then?

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kens
(Note: this explanation only makes sense if you're looking at the diagram in
the Z-80 article [1]).

> How does A being high connect the yellow to ground exactly if it doesn't
> cross the yellow strip?

The transistor gates are the green lines. Line A (polysilicon) is colored both
pink and green; it's green where it is a gate and pink where it's just a wire.
A signal can only cross the green line (gate) if the transistor is on. So if A
is on, the yellow dot is connected to ground (via transistor 1). If B is on,
the yellow dot is connected to ground (transistor 2), and so on. The yellow
dot is a connection between the silicon and the metal strip (yellow) on top.

The yellow metal strip ties together the three yellow dots, so it will be
grounded if A or B or C is high.

But that's only part of the gate. The output (where the resistor is) will be
connected to the yellow metal strip if transistor 4 (D) or transistor 5 (E) is
on. So the final logic function ends up being rather complex. The point is
that MOS gates let you build complex AND/OR functions just as easily as a
simple gate.

> Is the yellow metal line much much shorter than all the other vertical lines
> then?

Yes. The yellow metal strip is just internal wiring for the gate. The other
vertical metal strips are long-distance routing from one part of the chip to
another. For instance, the blue (ground) metal line goes all through the chip.

> Why does input line "A" not cross the yellow metal line but the other 3 do?

That's really just coincidence. A, B, and C are polysilicon wires, and they
are separated from the metal layer by an insulating oxide layer. Think of the
metal layer as an overpass above A, B, and C. On the other hand, if
polysilicon crosses doped silicon (cyan), you end up with a transistor, so
those crossings are very important. I indicate those crossings by changing the
line color to green.

It's hard to keep track of what's happening in the different layers. I
probably should have made the explanation a bit more detailed.

[1]:
[http://www.righto.com/2013/09/understanding-z-80-processor-o...](http://www.righto.com/2013/09/understanding-z-80-processor-
one-gate.html)

~~~
bogomipz
>"The transistor gates are the green lines. Line A (polysilicon) is colored
both pink and green; it's green where it is a gate and pink where it's just a
wire."

Thanks so much for this explanation. The input and output lines in schematic
diagrams have always vexed me. The disconnect between how a transistor is
often represented as a standalone 3D graphic such as you have above and how
its actually implemented is silicon being the source of my confusion. Have you
considered turning these z80 blog posts into a book? You have a great way of
explaining things. Cheers.

