New "Note for older host platforms" section between the SM86 long-ctx
note and the WSL2 section. Documents the 30-40% TP=2 throughput hit
that PCIe Gen 3 + pre-Zen3 / pre-2018 Xeon rigs see vs the reference
Gen 4 / Ryzen 5950X / EPYC rigs in BENCHMARKS.md.
Covers:
- Two compounding causes (PCIe bandwidth halved, weaker CPU per-core).
- Symptom (asymmetric GPU util during decode — communication-starved
TP=2).
- Three concrete mitigations: enable persistence mode, prefer single-
card paths over dual.yml, raise host RAM allocation on VMs.
- Worked example linking to issue #137 (Xeon Gold 6138 + Gen 3) and
@lolren disc #18 (Ryzen 5950X + Gen 4) for the side-by-side.
Follows from comment on #137 that promised this addition.
Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>
