micheleandClaude Sonnet 5
5f0d7f101c
Implements M3: three parametric dual-port buffers for the §12 data-plane (Input/Weight/Result), reusing the proven BRAM-inference idiom from the frozen hardware/v1/rtl/act_buffer.v (synchronous write, synchronous REGISTERED read, no reset on the read register -- keeps Yosys off the LUT-RAM path). Verified with Verilator: 10/10 tests pass (write-then-read correctness, extreme INT8 round-tripping, weight_buffer's full 64-bit tile width round-tripping, undisturbed re-reads). Real synthesis at two depths per module (6 configs total): 0 CHECK problems, every configuration correctly infers DP16KD (never LUT-RAM). Non-obvious real finding: weight_buffer's BRAM cost is driven by its P_IN*DATA_WIDTH tile width, not its DEPTH -- an 8x depth reduction (512->64) left DP16KD usage unchanged at 2, while activation_buffer/result_buffer (byte-wide) scale as naively expected (2->1). All default-depth configs PASS at 80MHz with large margin (287-367 MHz) via real nextpnr-ecp5 place&route. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_013xXuuRUWZScuo1DeYJxs3v
62 lines
3.2 KiB
Plaintext
62 lines
3.2 KiB
Plaintext
# V2 benchmark log -- solo append, mai troncato/sovrascritto (vedi README.md)
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# Nessuna entry ancora -- popolato incrementalmente man mano che avanza lo sviluppo V2.
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[2026-09-05] M1 single Neural Processor, isolated (no array/director/
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memory manager yet -- system-level numbers deferred to M9)
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| Config | Fmax (POST-P&R) | LUT | FF | DSP | BRAM |
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|----------------------|------------------|-----|-----|-----|------|
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| P_IN=8, ACC_WIDTH=32 | 183.12 MHz | 55 | 533 | 8 | 0 |
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| P_IN=8, ACC_WIDTH=24 | 176.21 MHz | 49 | 509 | 8 | 0 |
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Reference (V1, hardware/v1/synthesis/p8/, isolated neuron_parallel,
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PARALLEL=8, N_INPUTS=256): 61.71 MHz POST-P&R.
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All Fmax figures above are POST-P&R (real nextpnr-ecp5), not
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theoretical or simulated-only. MAC/cycle, cycles/neuron, neurons/s,
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stall %, effective MAC/s: not yet meaningful at this milestone (single
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isolated processor, no streaming benchmark harness yet -- deferred to
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M2 once neural_processor_array.v exists and a real workload can be
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timed end-to-end).
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[2026-09-05] M2 Neural Processor Array, N_PROCESSORS sweep (P_IN=8,
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ACC_WIDTH=32 each; synthesized via the timing harness, see errors.log
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ERR-0005 for why)
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| N_PROCESSORS | Fmax (POST-P&R) | LUT | FF | DSP (MULT18X18D) | DSP % of 72 |
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|--------------|------------------|-----|------|-------------------|-------------|
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| 1 | 159.11 MHz | 59 | 409 | 8 | 11% |
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| 2 | 149.59 MHz | 106 | 786 | 16 | 22% |
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| 4 | 151.01 MHz | 207 | 1540 | 32 | 44% |
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| 8 | 134.70 MHz | 374 | 3048 | 64 | 88% |
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All figures POST-P&R (real nextpnr-ecp5), all PASS at the 80MHz
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target. LUT4 utilization stays under 6% of the device even at N=8;
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DSP is the binding resource (see decisions.log DEC-0005), reaching 88%
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at N=8 -- N_PROCESSORS=9 would already exceed the LFE5U-45F's 72
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MULT18X18D budget at P_IN=8. Theoretical MAC/cycle (THEORETICAL, not
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yet measured end-to-end -- no real workload/benchmark harness exists
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until M9): N_PROCESSORS * P_IN MACs/cycle when all processors are
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simultaneously streaming tiles (8, 16, 32, 64 for N=1/2/4/8 -- verified
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achievable in principle by EXP-0003's concurrent/staggered simulation,
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not yet measured as a sustained throughput number).
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[2026-09-05] M3 buffers -- BRAM cost vs DEPTH (real Yosys synth_ecp5)
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| Module | DEPTH | DP16KD | LUT4 | FF |
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|--------------------|-------|--------|------|-----|
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| activation_buffer | 4096 | 2 | 37 | 30 |
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| activation_buffer | 256 | 1 | 21 | 26 |
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| weight_buffer | 512 | 2 | 88 | 139 |
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| weight_buffer | 64 | 2 | 73 | 136 |
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| result_buffer | 4096 | 2 | 37 | 30 |
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| result_buffer | 256 | 1 | 21 | 26 |
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weight_buffer's DP16KD count is flat across an 8x depth reduction --
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its 64-bit TILE_WIDTH (P_IN=8 * DATA_WIDTH=8), not DEPTH, determines
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BRAM count for this module. activation_buffer/result_buffer (byte-
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wide) scale as expected with depth. Confirms §14's warning literally:
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"non assumere che buffer piu' grandi siano automaticamente migliori"
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-- here, smaller was not cheaper either, because depth was the wrong
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lever for this specific buffer's cost.
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