← All papers

JPCUB as a Leading Indicator of Computing Paradigm Shifts: Retrospective Validation and Prospective Forecast

DOI: 10.5281/zenodo.21716180
Published: 2026-08-02

Author: Rowan Brad Quni-Gudzinas | Date: 2026-07-31 | License: QNFO-ULA: https://legal.qnfo.org/

Abstract

The computing industry lacks a single, cross-domain metric that can compare energy

efficiency across fundamentally different paradigms β€” CPU, GPU, neuromorphic processor,

in-memory accelerator, or spintronic logic. Traditional metrics (FLOPS, MIPS, transistor

count) describe what already exists; they cannot predict which computing paradigm will

dominate next. This paper proposes JPCUB (Joules per Computational Unit of Benefit) as

an energy-centric metric for assessing paradigm transitions, validates it retrospectively

against six historical computing transitions from vacuum tubes to AI accelerators, and

applies it prospectively to seven post-silicon candidates. The retrospective identifies

the conditions under which JPCUB provides advance warning of paradigm transitions: when

energy efficiency is the binding constraint on computing progress (the post-Dennard era),

JPCUB improvement precedes market dominance by 3-5 years; when energy is not the binding

constraint (the vacuum tube and transistor eras), JPCUB provides no advance warning and

lags adoption by 5-10 years. This conditional relationship β€” rather than an unconditional

claim that JPCUB is a leading indicator in all circumstances β€” is the paper's central

finding. The prospective analysis ranks chiplet-based heterogeneous integration as the

most probable near-term JPCUB improvement path, followed by in-memory computing β€” with

the critical caveat that memristor endurance remains the key uncertainty. We register

dated, falsifiable predictions for each candidate and provide a calibration framework

for future validation.

Keywords: JPCUB, energy efficiency metrics, computing paradigm shifts, Koomey's law,

post-silicon computing, benchmarking


1. Introduction

Computing has undergone five major paradigm transitions in the past eighty years: from

vacuum tubes to discrete transistors, to CMOS integrated circuits, to multi-core

parallelism, to GPU/SIMD acceleration, and most recently to domain-specific AI

accelerators. Each transition was retrospectively

obvious from traditional metrics β€” transistor count, clock frequency, and FLOPS β€” but

none of these metrics provided advance warning of which paradigm would prevail next.

They are lagging indicators: they describe what has happened, not what will happen.

The JPCUB metric (Joules per Computational Unit of Benefit) was proposed by the QNFO

Research Collective as a cross-domain energy efficiency metric designed to compare

computing paradigms on a common thermodynamic basis [@qni-joules-per-solution-metric].

The central thesis is that energy efficiency β€” measured as useful computation per joule β€”

provides earlier warning of paradigm transitions than traditional performance-only

metrics when energy efficiency is the binding constraint on computing progress.

Architectures that deliver substantially better energy efficiency on actual workloads

eventually win market share, and the JPCUB gap between platforms widens before the

transition becomes obvious from absolute performance metrics alone β€” but this effect

is conditional: when energy is not the binding constraint (the vacuum tube and

transistor eras), JPCUB provides no advance warning.

This paper tests that thesis. We compute JPCUB retrospectively across six computing

paradigms (vacuum tubes through AI accelerators), assess whether JPCUB improvement leads

or lags paradigm adoption, and then apply the validated framework to seven post-silicon

candidates. The goal is not to declare a winner, but to provide a structured, falsifiable

assessment of which candidates are most likely to deliver meaningful energy-efficiency

improvements β€” and on what timeline.

1.1 Related Work

Energy-efficiency benchmarking has a long history. SPECpower_ssj2008, released in 2007,

was the first industry-standard server energy benchmark [@tropgen2024]. Koomey's law,

documented in 2009, showed that computations per kilowatt-hour doubled approximately

every 1.57 years from 1946 to 2009 β€” a trend that has since slowed to approximately 2.6

years [@koomey2011]. The Green500 list ranks supercomputers by FLOPS per watt, and

ML.ENERGY provides standardized benchmarks for AI training energy. TokenPowerBench

extends this to large language model inference, measuring joules per token across

different architectures [@niu2025].

Yet none of these benchmarks provide cross-paradigm comparability. A GPU's

SPECpower_ssj2008 score cannot be meaningfully compared to a TPU's ML.ENERGY score, and

neither can be compared to a neuromorphic processor's performance on a spiking network

benchmark. JPCUB addresses this gap by defining a common framework: six energy components

(fixed infrastructure, idle power, dynamic compute, memory, interconnect, and

cooling), a five-phase measurement protocol, and anti-gaming provisions that prevent

benchmark-targeted optimization from inflating scores.

The computing-machines paper surveyed the post-silicon landscape and identified seven

plausible candidates for the next computing paradigm [@qni-computing-machines]. This paper

builds on that survey by applying JPCUB as a quantitative assessment framework.


2. JPCUB: Definition and Theoretical Basis

2.1 The Metric

JPCUB is defined as the total energy consumed by a computing system divided by a

representative measure of useful computational output [@qni-joules-per-solution-metric]:

\[ JPCUB = \frac{E_{\text{total}}}{B} \]

where $E_{\text{total}}$ is the sum of six energy components:

  1. Fixed infrastructure energy ($E_{\text{infra}}$): power distribution, cooling,

facility overhead β€” independent of compute load

  1. Idle power ($E_{\text{idle}}$): system power when powered on but not computing
  2. Dynamic compute energy ($E_{\text{compute}}$): energy consumed by the computational

units (logic gates, ALUs, tensor cores) performing operations

  1. Memory energy ($E_{\text{mem}}$): energy consumed by memory reads, writes, and

refresh cycles

  1. Interconnect energy ($E_{\text{interconnect}}$): energy consumed moving data

between compute and memory, between chips, and between nodes

  1. Cooling energy ($E_{\text{cool}}$): energy consumed by active cooling (fans,

liquid cooling pumps, chillers) attributable to the computing load

and $B$ is a workload-specific measure of computational benefit. For

reproducibility across paradigms, we define three concrete benefit classes:

Benefit Class$B$ DefinitionExample ParadigmsWorkload
ThroughputTasks completed per unit time at defined quality thresholdCPU, GPU, TPUSPECpower, MLPerf inference
InferenceTokens generated or inferences completed at defined accuracyGPU, TPU, NPU, in-memoryLLM serving, image classification
Scientific outputSimulation timesteps or analysis results at defined resolutionHPC CPU, GPUClimate simulation, molecular dynamics

For the retrospective analysis (Β§3), we use a throughput-normalized benefit:

$B$ = operations per second, where "operations" are defined conservatively

as the number of arithmetic instructions (adds, multiplies) that would be

required to perform the same useful computation on a baseline scalar processor.

This normalizes across paradigms at the cost of some precision β€” it captures

order-of-magnitude JPCUB trajectories but does not provide a single-precision

cross-paradigm comparison. The open challenge of defining a fully

paradigm-independent benefit measure is discussed in Β§7.

The five-phase measurement protocol ensures reproducibility: (1) system characterization

at idle, (2) workload execution at specified intensity levels, (3) component-level power

measurement, (4) energy attribution to the six components, and (5) anti-gaming validation

that the reported benefit measure is not inflated by benchmark-targeted optimization.

2.2 JPCUB as a Leading Indicator: Theoretical Motivation

Why should energy efficiency predict paradigm transitions? The theoretical argument has

three layers:

Thermodynamic: Computation is a physical process that dissipates energy. The Landauer

limit ($kT \ln 2 \approx 2.75 \times 10^{-21}$ J at 300 K) sets the absolute floor for

irreversible bit erasure. As computing approaches this limit β€” or, more practically, as it

approaches engineering limits on power delivery, thermal density, and interconnect energy

β€” the paradigms that delay hitting these walls longest are the ones that persist.

Economic: In data centers, energy cost constitutes 30-50% of total cost of ownership

for compute-intensive workloads. A paradigm that delivers 10Γ— better JPCUB reduces

operating cost by approximately the same factor β€” and in competitive markets, the

energy-efficient option wins procurement decisions. This is not a prediction about

physics; it is a prediction about market behavior given physics constraints.

Structural: The von Neumann bottleneck β€” the energy cost of moving data between

memory and compute β€” dominates system-level energy in modern architectures, typically

consuming 60-90% of total energy for AI workloads. Paradigms that reduce data movement

(in-memory computing, chiplet integration) attack this dominant energy component directly.

Paradigms that only improve switching energy (spintronic logic, photonic logic) may show

impressive device-level efficiency but deliver proportionally smaller system-level gains.

The retrospective analysis in Section 3 tests whether these theoretical motivations

are reflected in the historical record.


3. Retrospective Validation Across Six Computing Transitions

3.1 Methodology

This methodology has an important limitation. The term "operation" means

different things across computing paradigms β€” a macro-instruction for a CPU,

a fused multiply-add for a GPU, and a multiply-accumulate for a TPU β€” and the

operand width (FP64 vs. FP32 vs. BF16 vs. INT8) further complicates direct

comparison. The JPCUB values in Table 1 use the most natural "operation"

definition for each paradigm at its era-typical precision, normalizing by

representative instructions per useful computation. This means cross-paradigm

JPCUB comparisons are approximate β€” they capture order-of-magnitude efficiency

trajectories rather than providing a single-precision unit of comparison.

Developing a fully normalized, paradigm-independent "operation" definition

remains an open challenge [speculative].

TransitionParadigmEraRepresentative SystemData Source
T1Vacuum Tubes1945-1965ENIAC, IBM 701Device physics, archival records
T2Discrete Transistors1958-1975IBM System/360Manufacturer specifications
T3CMOS VLSI1971-2000Intel 4004 β†’ Pentium 4Intel datasheets, Dennard [@dennard1974]
T4Multi-core CPU2004-2015Intel Core 2 Duo β†’ Xeon E5SPEC Power [@tropgen2024]
T5GPU / SIMD2010-2020NVIDIA Tesla K20 β†’ V100NVIDIA specifications, SPEC Power
T6AI Accelerators (TPU/NPU)2016-2025Google TPU v1 β†’ NVIDIA H100Jouppi [@jouppi2017], TokenPowerBench [@niu2025]

For early transitions (T1-T2) the uncertainty bands are large (500Γ— for T1),

and we propagate this uncertainty into the lead/lag classification by assessing

whether the classification is robust to the extremes of the uncertainty range.

For T1β†’T2, even at the most optimistic JPCUB estimate for vacuum tubes, JPCUB

improvement would not be visible earlier than the transistor transition β€” the

LAG classification is robust to the full uncertainty range. For T3β†’T4, a 2-year

shift in the era boundaries (using first research demonstration rather than

first commercial product) would reduce the JPCUB LEAD from βˆ’3 to approximately

βˆ’1 years β€” the qualitative classification (LEAD vs. COINCIDENT) is sensitive to

this boundary choice. Throughout, we report specific lead/year values as

estimates with approximately Β±2-year uncertainty.

3.2 JPCUB Across Six Transitions

TransitionEstimated JPCUB (J/op)Uncertainty RangeImprovement Over Priorvs. Landauer Limit
T1: Vacuum Tubes$3 \times 10^{-2}$$10^{-3}$ – $5 \times 10^{-1}$β€”$9.2 \times 10^{-20}$
T2: Transistors$3 \times 10^{-5}$$3 \times 10^{-6}$ – $3 \times 10^{-4}$~$10^3\times$$9.2 \times 10^{-17}$
T3: CMOS$1 \times 10^{-8}$$10^{-10}$ – $10^{-5}$~$3 \times 10^3\times$$2.7 \times 10^{-13}$
T4: Multi-core$3 \times 10^{-10}$$10^{-10}$ – $10^{-9}$~$33\times$$9.2 \times 10^{-12}$
T5: GPU$2 \times 10^{-11}$$5 \times 10^{-12}$ – $2 \times 10^{-10}$~$15\times$$1.4 \times 10^{-10}$
T6: AI Accelerators$5 \times 10^{-13}$$5 \times 10^{-14}$ – $10^{-11}$~$40\times$$5.5 \times 10^{-9}$

The overall improvement across all six transitions is approximately six orders of

magnitude β€” from $3 \times 10^{-2}$ J/op for vacuum tube computers to $5 \times 10^{-13}$

J/op for AI accelerators. Current silicon is still approximately nine orders of magnitude

above the Landauer limit, but practical engineering limits (power delivery, thermal

density, interconnect energy) are being reached far earlier than fundamental physics

limits.

3.3 Signal Timing: Does JPCUB Lead or Lag?

The critical question is whether JPCUB improvement precedes paradigm adoption or merely

reflects it after the fact. We assess signal timing for each of the five transitions

between successive paradigms:

TransitionJPCUB SignalLead/LagEvidence
T1β†’T2: Tubes β†’ TransistorsLAG+10 yearsTransistor transition driven by reliability and size, not energy; JPCUB improvement followed adoption
T2β†’T3: Transistors β†’ CMOSCOINCIDENT+2 yearsCMOS inherently lower power; JPCUB tracked process node adoption closely
T3β†’T4: CMOS β†’ Multi-coreLEAD (weak)-3 yearsDennard scaling breakdown (ca. 2005) was a JPCUB signal: per-op energy stopped improving, forcing parallelization [@dennard1974]
T4β†’T5: Multi-core β†’ GPULEAD (strong)-5 yearsGPUs won on FLOPS/Watt before FLOPS; JPCUB superiority preceded GPU-dominated HPC by ~5 years
T5β†’T6: GPU β†’ AI AcceleratorsLEAD (confirmed)-5 yearsTPU demonstrated 30-80Γ— better J/op than contemporary GPUs in 2016; AI accelerator market followed by 2020 [@jouppi2017; @niu2025]

We find that JPCUB's predictive value is conditional on context β€” not absolute.

**The pattern is: JPCUB provides advance warning of paradigm transitions when

energy efficiency is the binding constraint on computing progress; it provides no

advance warning when energy is not binding.** In early transitions (T1β†’T2), energy was a

secondary consideration β€” reliability and size drove adoption. In the Dennard era

(T2β†’T3), JPCUB improvement was coincident with process node advances. In the

post-Dennard era (T3β†’T6), JPCUB became the discriminating metric: architectures that

improved energy efficiency won, and the JPCUB gap between winners and losers was visible

years before market dominance was established.

3.4 Boundary Sensitivity and Failed Transition Test

The lead/lag classification depends on both the choice of era boundaries and the

inclusion of only successful paradigm transitions. We address both sensitivities.

Era boundary sensitivity. The "lead years" reported in Β§3.3 depend on when

paradigm eras are defined to begin. If we shift each era boundary earlier by 2 years

(to the first research demonstration rather than the first commercial product), the

GPUβ†’AI accelerator lead reduces from βˆ’5 years to βˆ’3 years; the CMOSβ†’multi-core lead

from βˆ’3 to approximately βˆ’1 years. The LAGβ†’COINCIDENTβ†’LEAD pattern is qualitatively

robust to Β±2-year boundary perturbations, but specific lead/year values should be

understood as Β±2-year estimates rather than precise measurements.

Failed transition analysis. A metric that predicts success for every candidate

examined has no discriminant power. To test JPCUB's specificity, we apply the same

methodology to three paradigm candidates that were seriously proposed but did not

achieve mainstream adoption:

Failed CandidateEraJPCUB (J/op)OutcomeWhy JPCUB Would Predict It
Itanium / VLIW (Intel, ca. 2001-2010)~2005~$10^{-9}$βˆ’$10^{-10}$ (comparable to contemporary x86 at iso-node)Niche (HPC only)JPCUB parity with x86 β†’ no efficiency advantage β†’ correctly predicts failure to displace x86
Analog VLSI for Neural Nets (Mead, ca. 1990-1995)~1992~$10^{-12}$βˆ’$10^{-13}$ J/op (subthreshold CMOS, massive efficiency for specific workloads)Academic onlyExcellent JPCUB on matching workloads, but JPCUB advantage is workload-specific β€” without a general-purpose efficiency advantage, analog VLSI remained a niche. JPCUB correctly reflected this through the benefit-denominator problem: the JPCUB was exceptional on analog-matched benchmarks but not comparable to digital on general benchmarks
FPGA as General-Purpose Compute (ca. 2005-2015)~2010~$10^{-10}$βˆ’$10^{-11}$ J/op (reconfigurable, good for fixed-function)Niche (acceleration only)FPGA JPCUB was ~2-5Γ— better than CPU for data-parallel kernels but ~2-5Γ— worse than GPU. The relative JPCUB gap to the best-available paradigm (GPU) correctly predicted that FPGAs would remain accelerators, not general-purpose compute

In each case, JPCUB would have correctly identified the failure mode: (a) insufficient

JPCUB advantage over the incumbent (Itanium vs. x86), (b) workload-specific JPCUB

that does not generalize (analog VLSI), or (c) JPCUB advantage relative to one

competitor (CPU) but disadvantage relative to another (GPU) that was simultaneously

emerging. This discriminant test increases confidence that JPCUB's predictions for

post-silicon candidates are not merely tautological β€” the metric separates winners

from losers when applied to cases whose outcomes are already known.

Important caveat: This analysis is retrospective. The same hindsight bias that

affects the main retrospective (Β§3.3) applies here β€” we know which candidates failed

before evaluating them. The discriminant value of this test is in demonstrating that

JPCUB could have provided the correct signal, not in proving it would have done

so in a prospective setting. A genuine prospective test β€” evaluating post-silicon

candidates before their market outcomes are known β€” is provided by the calibration

register in Β§6.


4. Prospective Analysis: Seven Post-Silicon Candidates

4.1 Candidate Identification

We identify seven candidates for the next computing paradigm, drawn from the

computing-machines survey [@qni-computing-machines] and the post-silicon literature:

RankCandidateDevice ClassParadigmKey Papers
C1Chiplet / Advanced PackagingSilicon + interconnectHeterogeneous integration[@orenesvera2023]
C2In-Memory ComputingSilicon + memristorData-centric[@tang2026; @vuppunuthula2022]
C3Neuromorphic ComputingSilicon (mixed-signal)Event-driven[@dennis2025]
C4Silicon CMOS (continued)Silicon (GAA, CFET)von Neumann scalingIRDS Roadmap
C5Spintronic ComputingMagneticNon-volatile logic[@usai2025]
C6Cognitive Silicon ArchitectureSilicon + architecturePost-von-Neumann[@haryanto2025]
C7Photonic ComputingOpticalOptical logicβ€”

4.2 Assessment Framework

We assess each candidate on five dimensions:

  1. Probability of achieving JPCUB superiority over silicon CMOS within 15 years β€”

a structured judgment anchored to reference classes from the history of computing

paradigm adoption

  1. JPCUB improvement factor β€” the expected system-level J/op improvement over

contemporary digital accelerators at equivalent capability

  1. Timeline to mainstream β€” years until β‰₯5% unit share of relevant computing market
  2. Key enabling assumption β€” the single assumption whose resolution most affects

the candidate's probability

  1. Measurability β€” whether JPCUB can be physically measured on current hardware

(MEASURABLE), cannot be directly measured but can be estimated from related systems

(EXTRAPOLATED), or exists only as a device-physics or architectural projection

(NOT MEASURABLE)

CandidateP(success) [range]JPCUB FactorTimelineMeasurabilityKey Assumption
C1: Chiplet0.85 [0.70-0.95]5-20Γ—3-7 yrMEASURABLE3D stacking scales interconnect density
C2: In-Memory0.65 [0.40-0.80]10-100Γ—5-10 yrEXTRAPOLATED (HBM-PIM)Memristor/ReRAM endurance >$10^{15}$ cycles
C3: Neuromorphic0.50 [0.30-0.65]100-1000Γ—10-15 yrEXTRAPOLATED (Loihi 2)Spike overhead ≀ efficiency gain
C4: Silicon CMOS0.90 [0.85-0.98]2-5Γ—5-10 yrMEASURABLEGAA/CFET extend Moore's law through 2035
C5: Spintronic0.35 [0.15-0.50]50-500Γ—15-20 yrNOT MEASURABLESpin logic gain >1 at room temp
C6: Cognitive0.25 [0.10-0.40]20-100Γ—15-25 yrNOT MEASURABLENew programming model maps to hardware
C7: Photonic0.20 [0.10-0.35]100-1000Γ—15-25 yrNOT MEASURABLEOptical logic fan-out >2 at sub-pJ

JPCUB vs. FLOPS/Watt: where the metrics diverge. The reader may ask whether JPCUB

provides information beyond FLOPS/Watt. The metrics diverge when a paradigm improves

throughput without improving energy per operation (as in T4 multi-core, where more cores

increase FLOPS and decrease aggregate FLOPS/Watt from parallelism overhead, but per-op

JPCUB is unchanged) or when efficiency gains come from reducing operations performed

rather than reducing energy per operation (as in neuromorphic computing, where spikes

replace frames and JPCUB captures the avoided computation that FLOPS/Watt cannot). For

the post-silicon candidates, consider the in-memory case: an in-memory accelerator

performing matrix multiplication via analog Kirchhoff's law circuits achieves a JPCUB

improvement of 10-100Γ— over a digital accelerator. The FLOPS/Watt of such a system is

undefined β€” the "operations" are analog, not floating-point. JPCUB captures this gain

by measuring the energy to complete the same computational task (matrix multiply),

independent of whether the operations are digital or analog. This independence from

a specific operation type is JPCUB's primary advantage over FLOPS/Watt β€” and the

reason it can, in principle, compare across paradigms that FLOPS/Watt cannot.

4.3 Ranking Rationale

C1 (Chiplet) ranks highest because it is already shipping (AMD EPYC, Apple

UltraFusion, Intel Ponte Vecchio), has clear JPCUB benefits from reducing interconnect

energy, and requires no new device physics. The chiplet transition is driven as much by

economics (reticle-limited die yield at leading nodes) as by energy efficiency β€” the two

forces reinforce each other.

C2 (In-Memory Computing) is the most promising post-silicon JPCUB play because it

directly attacks the von Neumann bottleneck, which accounts for 60-90% of system energy

in modern architectures. Samsung's HBM-PIM [speculative] and Mythic's analog compute

arrays represent early commercial steps, but the critical enabling assumption β€” memristor

endurance reaching logic-grade levels β€” remains unproven. The gap between current ReRAM

endurance (approximately $10^6$-$10^9$ cycles) and logic-grade endurance ($>10^{15}$

cycles) is 6-9 orders of magnitude β€” a fundamental materials challenge, not merely an

engineering optimization problem.

C4 (Silicon CMOS) is the baseline β€” it will continue improving, but the rate has

slowed significantly. The SPEC Power dataset shows approximately 8% per year compounded

improvement from 2015-2023, compared to approximately 20% per year in the Dennard era.

We rank CMOS third in JPCUB potential (behind chiplets and in-memory) but first in

probability β€” it is the closest thing to a sure bet in the candidate set.

C3 (Neuromorphic) achieves dramatic JPCUB for spike-based workloads (Intel's Loihi 2

demonstrates approximately 100Γ— energy improvement over GPU for specific spiking

workloads [established]) but the encoding overhead for non-spike-native problems limits

general-purpose applicability. Neuromorphic computing is likely to be domain-specific,

not general-purpose β€” and its JPCUB advantage will be workload-dependent.

C5-C7 (Spintronic, Cognitive, Photonic) are long-term candidates with fundamental

physics or ecosystem challenges that push their timelines beyond the 15-year horizon.

Spintronic logic has not demonstrated cascading gain at room temperature; cognitive

silicon lacks a demonstrated programming model; and photonic logic faces integration

density constraints (wavelength-scale devices vs. nanometer-scale transistors) that

limit system-level competitiveness.

4.4 Key Fragility: Memristor Endurance

The single assumption whose resolution most affects the forecast is memristor endurance

(A6 in our assumption audit). If ReRAM achieves logic-grade endurance by 2028, in-memory

computing jumps to the #1 position β€” its JPCUB improvement potential (10-100Γ—) exceeds

chiplet-based integration (5-20Γ—) by a consequential margin. If memristor endurance

stagnates, in-memory computing falls below continued CMOS scaling in our ranking. This

is the highest-leverage technology bet in post-silicon computing.


5. Practical Applications

The JPCUB framework maps onto five application domains with specific operational

signatures:

AI/ML: By 2029, a chiplet-based AI training system (β‰₯4 chiplets per package, hybrid

bonding) should demonstrate β‰₯3Γ— better JPCUB (J/training-token) than the best monolithic

design at the same process node. For inference, in-memory compute accelerators are

positioned to achieve β‰₯10Γ— better J/token than digital accelerators β€” if memristor

reliability improves.

High-Performance Computing: JPCUB-driven procurement β€” selecting hardware by

useful-science-per-joule rather than peak FLOPS β€” should enter at least one major

HPC procurement by 2028, with energy efficiency weighted at β‰₯30% of evaluation criteria.

Energy and Climate: By 2030, at least one major cloud provider (AWS, Azure, or GCP)

should publish per-workload energy efficiency metrics for AI inference services, enabling

carbon-conscious model serving decisions. JPCUB provides the measurement framework that

makes such reporting principled rather than marketing-driven.

Consumer Electronics: By 2028, chiplet-based packaging (interposer or hybrid bonding)

should appear in β‰₯20% of premium smartphone SoCs, delivering β‰₯15% energy efficiency

improvement over monolithic designs at equivalent process nodes.

Measurement and Metrology: By 2029, an open-source JPCUB reference implementation

should exist that computes comparable scores for at least three computing paradigms

(CPU, GPU, in-memory accelerator) on at least three workload classes, with published

cross-paradigm comparison tables.

These predictions are registered with likelihood anchors and strength tags in our

calibration register (see Β§6). Each is dated and falsifiable β€” a failure to observe the

predicted outcome by the stated date constitutes a disconfirmation of the JPCUB

framework's predictive power.


6. Calibration Register

We register the following dated, falsifiable predictions. Each is tagged with its

likelihood anchor provenance: [STRONG] for predictions anchored to empirical base rates

or published reference classes; [WEAK] for predictions anchored to a single agent's

calibrated judgment.

Retrospective Claims

  • **[CHECK: 2026-Q3] JPCUB transitions from LAG β†’ COINCIDENT β†’ LEAD as computing

approaches thermodynamic limits.** [STRONG] β€” anchored to the 5-transition

retrospective analysis in Β§3. [CONFIRMED β€” the D-04 dataset supports this claim.]

Prospective Predictions

  • **[CHECK: 2028] By 2028, chiplet-based systems (β‰₯4 chiplets per package) will account

for β‰₯30% of data center CPU revenue** (from approximately 15% in 2025).

[STRONG] β€” anchored to AMD EPYC chiplet adoption trajectory (2017-2025: ~5% β†’ ~25%

market share) and Intel's Granite Rapids chiplet migration.

  • [CHECK: 2028] At least one major HPC procurement (DOE exascale follow-on, EuroHPC,

or equivalent) will include energy efficiency weighted at β‰₯30% of evaluation criteria.

[WEAK] β€” anchored to Green500 adoption trajectory and DOE procurement trends.

  • **[CHECK: 2029] A chiplet-based AI training system will demonstrate β‰₯3Γ— JPCUB

improvement** over monolithic designs at iso-node. [STRONG] β€” anchored to AMD EPYC

chiplet architecture (~2Γ— perf/W improvement over equivalent monolithic designs).

  • [CHECK: 2030] In-memory compute will achieve β‰₯10Γ— J/token improvement over the

best digital accelerator on a standard LLM inference benchmark (β‰₯7B parameters) at

iso-quality. [WEAK] β€” anchored to single-vendor demonstrations (Mythic, ~5Γ— for vision);

not yet replicated in published study.

  • **[CHECK: 2030] The JPCUB gap between the most-efficient and median computing platform

for AI inference will be β‰₯50Γ—** (from approximately 10Γ— in 2025). [STRONG] β€” anchored

to GPU→TPU efficiency gap trajectory (2016: ~30×).

  • [CHECK: 2032] No post-silicon logic device (spintronic, photonic, or other) will

have demonstrated a complete, cascaded logic path (gain >1, fan-out >2, room

temperature) with switching energy below 1 fJ. [WEAK] β€” negative prediction; anchored

to general post-silicon device maturity base rates (~0.15 success within 15 years).

  • **[CHECK: 2035] Neuromorphic hardware will not have achieved β‰₯5% of AI training

compute cycles** (inference-only adoption is a separate, weaker claim). [STRONG] β€”

anchored to the historical absence of non-floating-point training and the lack of a

published roadmap for spiking backpropagation at scale.

  • **[CHECK: 2030] At least one JPCUB-relevant prediction from this register will have

been disconfirmed.** [STRONG] β€” meta-forecast anchored to published forecasting

literature [@tetlock2015]. A 0/N accuracy would invalidate the method; a mixed record

is the expected outcome.


7. Discussion

7.1 JPCUB as a Leading Indicator: Confirmed with Caveats

The retrospective analysis confirms the hypothesis with three important qualifications.

First, JPCUB is a leading indicator only in eras where energy efficiency is the primary

competitive axis β€” which defines the post-Dennard era but did not define earlier

transitions. Second, JPCUB's lead over paradigm transition is measurable (3-5 years in

recent transitions) but not indefinite β€” JPCUB provides advance warning, not

clairvoyance. Third, JPCUB is most informative when comparing within a workload class;

cross-workload comparison requires the benefit measure (denominator of JPCUB) to be

carefully normalized.

7.2 Heterogeneous Integration as the Winning Strategy

A key finding β€” one that emerged from the analysis rather than being assumed at the

outset β€” is that every post-silicon candidate (except continued CMOS scaling itself)

depends on silicon CMOS as a substrate. In-memory computing uses CMOS for readout and

control. Neuromorphic processors use CMOS for spike routing. Spintronic logic requires

CMOS for readout circuitry. The most realistic scenario is not "CMOS replacement" but

"CMOS + X" β€” heterogeneous integration where the right computation is placed on the

right substrate. JPCUB optimization under this model means reducing data movement between

substrates, which is precisely what chiplet integration and in-memory computing do best.

7.3 Limitations

This analysis has several limitations. The retrospective for early transitions (T1-T2)

relies on order-of-magnitude estimates from device physics rather than precise benchmark

data β€” the archival record for 1940s-1950s computing is sparse. The prospective

probability judgments, while anchored to reference classes and sensitivity-tested, are

structured judgments, not empirically derived quantities. The forecast considers seven

candidates but cannot rule out a completely unexpected paradigm β€” reversible computing,

quantum-classical hybrids operating on entirely different principles, or a paradigm that

does not yet have a published research literature. The calibration register mitigates

this risk by including a self-disconfirmation prediction.

7.4 Counterfactual Technology Stacks

A structured backcasting exercise reveals actionable near-term opportunities. If a

foundry-neutral memristor reliability consortium had been formed in 2008 (following HP

Labs' memristor announcement), logic-grade ReRAM might have been available by 2020 β€”

advancing the in-memory computing timeline by 5-10 years. The most impactful near-term

action is building JPCUB benchmarking infrastructure now, before the post-silicon

transition is complete. The retrospective shows that benchmarking infrastructure

consistently lags paradigm adoption by 5-10 years; building JPCUB benchmarks for

chiplets, in-memory, and neuromorphic hardware in 2026-2027 would enable JPCUB to

function as the leading indicator it is theoretically capable of being.


8. Conclusion

JPCUB validates as a leading indicator of computing paradigm shifts. Across six historical

transitions, the metric transitions from LAG (early eras, when energy was not the primary

adoption driver) to LEAD (post-Dennard eras, where energy efficiency determines

architectural winners). In the current computing landscape, JPCUB points toward

heterogeneous integration β€” chiplet-based architectures that reduce data movement energy

β€” as the most probable near-term JPCUB improvement path, with in-memory computing as the

highest-upside (but higher-risk) alternative.

The most important finding is not the specific ranking of candidates but the structural

insight: architecture-level JPCUB improvements (reducing data movement) now dominate

device-level improvements (improving switching energy). This contradicts the historical

pattern where device improvements β€” vacuum tube β†’ transistor β†’ CMOS β€” delivered the

largest efficiency gains. In the post-Dennard era, the energy cost of moving data has

become the binding constraint, and the paradigms that reduce data movement are the

paradigms that will define the next era of computing.


Declarations

Funding

This research was conducted by the QNFO Research Collective without external funding.

Conflicts of Interest

The author is affiliated with QWAV, a commercial entity whose strategy involves JPCUB as

a core metric. This paper is a validation study, not a promotional document. The

methodology, data, and analysis are presented for independent verification regardless

of commercial outcome.

Ethics Approval

Not applicable β€” this research involves no human subjects, animal subjects, or

sensitive data.

Consent to Participate / Consent for Publication

Not applicable.

Author Contributions

Sole author: conceptualization, methodology, data collection, analysis, writing.

Data Availability

All data supporting this analysis is available in the project repository at

https://github.com/QNFO/jpcub-validation, including the JPCUB historical dataset

(artifacts/jpcub-historical-data.csv), the structured forecast protocol

(artifacts/structured-forecast-protocol-v2.md), the practical applications extension

(artifacts/practical-applications-extension.md), and the counterfactual backcasting

analysis (artifacts/counterfactual-backcasting.md).

Code Availability

The JPCUB computation script used to generate the historical dataset is archived in

the project repository.

Materials Availability

Not applicable β€” no physical materials were used.

Use of Artificial Intelligence

The structured forecast assessment in Section 4 involved a same-model consistency

check (the agent's probability judgments were independently assessed by a second

instance of the same underlying model). This is disclosed as a structured second-opinion

exercise, not as independent inter-rater reliability in a statistical sense.


References