C++20/23 · CUDA · EXL3 quants · no Python, no torch
Helios — a from-scratch engine family
One RTX 3090 sits on PCIe ×16 (≈25 GB/s); the other is stuck on ×4 (≈3.4 GB/s). No NVLink. An AVX2-only CPU. Forward pass, quantization kernels, KV cache, expert streaming and the HTTP server are all in the repo, because the interesting constraint is that slow link — and nobody else's default path respects it.
- 85 GB GLM-5.3-Flash on 48 GB of VRAM at the model's native 262k-token window.
- Qwen3.8-Flash-Next build: 1.28× exllamav3's prefill on the same machine — and it holds fp16 KV cache where the rival needs a 3-bit cache to reach the same context.
- Every variant ships with an honest results file before it ships a README — including the sections that start with "slower than baseline".
github.com/neron82/helios-glm53flash ↗ github.com/neron82/helios-qwen38next ↗
# the ×4 card is the most important fact: # anything crossing that link costs 7× the # same transfer on the ×16 card. place attention + hot experts → ×16 card stream cold experts from NVMe → pinned RAM tier KV cache, fp16 @ 262k → the model's own window verdict: measure first, optimize the lane that actually moves, ship or revert.

