Miniaturization replaced the tube with the transistor. The currency of compromise changed from watts of heater power to milliwatts of leakage and dissipation. The circuit remained a set of separate decisions, each of which could be touched, desoldered, rearranged. Compromises lived in four distinguishable layers, from the specification to the printed circuit board artwork.

Micro-miniaturization did not continue shrinking, it changed the method of packaging. The four layers were pressed into a fifth, the transfer of topology onto a substrate. Component choice, routing, power filtering ceased to be separate actions, they became a single lithographic pattern. The price for density turned out to be not size but loss of transparency. The overweight of the sum of compromises, previously visible on the board, moved inside the crystal.

Together with compression a bundle of feedback connections appeared. In a discrete circuit feedbacks were explicit, they could be cut with a probe. In an integrated circuit they became distributed, thermal, substrate, parasitic capacitive. The problem ceased to localize at a point, it began to drift through the network of compromises. Drift manifests not where it is born, noise in the speaker can start as a supply sag in another corner of the die, and bias instability as heating of a neighboring stage. The network itself becomes the channel for error transport.

Drift of the Problem Through the Network
Any circuit is a network of compromises linked by a bundle of feedbacks. Thermal, supply, parasitic capacitive, substrate. These connections are not drawn on the schematic, they arise as a consequence of placement. They form the transport network for error.

Drift is the movement of the place where a problem appears along this network. The problem is born at one point of the compromise layer, and becomes visible at another.

In miniaturization with discrete parts drift was slow and observable. Overheating of the output transistor changed the quiescent current of the input through the common supply rail, and this could be traced probe point by point. The bundle of feedbacks was sparse, so the drift trajectory was readable.

Micro-miniaturization compressed the network. The fifth layer, the transfer to substrate, made feedbacks dense and invisible. Heat from digital logic drifts through silicon to a low-noise input and appears as increased noise. A supply droop in a corner of the die drifts along the common ground and appears as a bias shift in another corner. Parasitic capacitance between adjacent tracks carries interference from output to input. Drift ceased to be movement across a board, it became movement across a field inside the crystal.

The key property of drift, it is not removed by local correction. An attempt to compensate the manifestation at the observation point does not touch the birth point. Therefore in an integrated circuit correcting bias in one stage often increases drift in another, because the bundle of feedbacks redistributes the overweight of the sum of compromises.

With the move to large-scale integration the network becomes even denser. Drift accelerates because distances are small and heat density is high. A problem born as a brief current spike can drift through the substrate and appear milliseconds later as a long-term frequency shift.

The Proxy Channel
The attempt to control this drift led to the idea of a proxy channel. In a superheterodyne the proxy is the intermediate frequency, the translation of a complex task into a region where filters are stable. In software-defined radio the proxy is digital, the translation of physics into numbers. For a circuit a proxy means taking the sum of compromises out of the physical layer into the informational, measuring currents and temperatures, digitizing the error and returning correction. While the circuit remained small-scale, the proxy could live outside. The transition to a pure large integrated circuit hid the proxy inside. It became part of the same fifth layer, and began to pay with heat and area for the right to treat heat and area.

This does not remove layers 1 to 5, but adds a sixth above them, where the compromise is no longer in die area but in the speed and accuracy of measurement. You pay not with heat but with processor cycles and memory for the model. Partially this already exists in digitally assisted analog, when an amplifier is calibrated by digital logic every millisecond. In full form a proxy channel would mean the circuit ceases to be a set of fixed compromises, it becomes a system that continuously translates its own errors into a convenient intermediate form and corrects itself there.

The Intermediate Form Between 2D and 3D
Between flat integration and volumetric integration an intermediate form appears, analogous to point-to-point wiring. This is not a track in metallization and not a through via, but a bridge over the substrate, under it, or along the die edge. An air bridge, a backside power delivery network, a silicon bridge between chiplets. Such a form returns part of controllability, allows bypassing an overloaded spot in the fifth layer without a full transition to a three-dimensional stack. It pays with lower repeatability, but gives the ability to spread compromises in space.

Atomization
The alternative path, conditional atomization, proposes not to compress the circuit but to grow a material with a given function. Here the layers of component choice and routing disappear, they are replaced by a layer of crystal synthesis. Compromises move from geometry to lattice physics, to purity, to homogeneity of the doping gradient, to domain stability. The drift of the problem also changes nature, it becomes a growth defect rather than a current shift. The bundle of feedbacks closes not through tracks but through internal fields of the material. The path requires a different currency, which at the moment of choice did not exist in controllable form. In atomization drift changes carrier. Instead of current along a conductor it is movement of a lattice defect or a domain wall in the material. The problem is born as growth non-uniformity and appears as a characteristic shift after hours of operation. The bundle of feedbacks here is the internal fields of the crystal, and drift through them cannot be stopped with a trimmer.

Conclusion
Thus evolution looks not like linear shrinkage but as a sequential change of where the overweight of compromises is stored. Miniaturization stored it in components, micro-miniaturization in the crystal plane, large integration in volume and in the built-in proxy, atomization would store it in the substance itself. Each step solved some forms of drift and created new ones, each step redistributed the bundle of feedbacks but did not eliminate it.

The choice between compression into a layer, offloading into a proxy, or growing into material remains open, because only the currency of payment changes, not the fact of payment itself.