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Top inference frameworks separate the prefill stage (ingesting the prompt, often compute-bound) from the decode stage (generating tokens, often memory-bound). This disaggregation allows for specialized hardware pools and scheduling for each phase, boosting overall efficiency and throughput.

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The AI inference process involves two distinct phases: "prefill" (reading the prompt, which is compute-bound) and "decode" (writing the response, which is memory-bound). NVIDIA GPUs excel at prefill, while companies like Grok optimize for decode. The Grok-NVIDIA deal signals a future of specialized, complementary hardware rather than one-size-fits-all chips.

The next wave of AI silicon may pivot from today's compute-heavy architectures to memory-centric ones optimized for inference. This fundamental shift would allow high-performance chips to be produced on older, more accessible 7-14nm manufacturing nodes, disrupting the current dependency on cutting-edge fabs.

Unlike simple classification (one pass), generative AI performs recursive inference. Each new token (word, pixel) requires a full pass through the model, turning a single prompt into a series of demanding computations. This makes inference a major, ongoing driver of GPU demand, rivaling training.

Simply "scaling up" (adding more GPUs to one model instance) hits a performance ceiling due to hardware and algorithmic limits. True large-scale inference requires "scaling out" (duplicating instances), creating a new systems problem of managing and optimizing across a distributed fleet.

Model architecture decisions directly impact inference performance. AI company Zyphra pre-selects target hardware and then chooses model parameters—such as a hidden dimension with many powers of two—to align with how GPUs split up workloads, maximizing efficiency from day one.

The intense power demands of AI inference will push data centers to adopt the "heterogeneous compute" model from mobile phones. Instead of a single GPU architecture, data centers will use disaggregated, specialized chips for different tasks to maximize power efficiency, creating a post-GPU era.

A fundamental constraint today is that the model architecture used for training must be the same as the one used for inference. Future breakthroughs could come from lifting this constraint. This would allow for specialized models: one optimized for compute-intensive training and another for memory-intensive serving.

While training has been the focus, user experience and revenue happen at inference. OpenAI's massive deal with chip startup Cerebrus is for faster inference, showing that response time is a critical competitive vector that determines if AI becomes utility infrastructure or remains a novelty.

A cost-effective AI architecture involves using a small, local model on the user's device to pre-process requests. This local AI can condense large inputs into an efficient, smaller prompt before sending it to the expensive, powerful cloud model, optimizing resource usage.

Unlike traditional computing where inputs were standardized, LLMs handle requests of varying lengths and produce outputs of non-deterministic duration. This unpredictability creates massive scheduling and memory management challenges on GPUs that were not designed for such chaotic, real-time workloads.

Modern AI Inference Systems Disaggregate 'Prefill' and 'Decode' Phases for Major Efficiency Gains | RiffOn