Files
FPGA-Neural/hardware/v2/rtl/neural_multiprocessor.v
micheleandClaude Sonnet 5 63cac6a7e5 perf(v2): shared activation cache - further 1.66-2.00x real speedup (DEC-0016)
Implements optimization #2 from the final benchmark campaign's own
recommendation, on top of DEC-0015's word-level burst rewrite: a new
shared activation_cache.v module fetches a given activation (X)
vector from PSRAM once instead of once per neuron sharing it - the
exact redundant traffic pattern the dense-layer workloads in this
project's benchmark suite exhibit.

Each memory_manager's own prefetch_engine now fetches WEIGHTS only;
the activation half is requested from the shared cache instead
(single-tag, tile-granular, N_SLOTS request ports, its own real
word-level PSRAM backend via a new dedicated arbiter port).
dataflow_core.v/slot_mem_arbiter.v/neural_multiprocessor.v widened to
N_SLOTS+1 ports to arbitrate the cache's traffic alongside each
slot's weight traffic.

Two real bugs found and fixed during implementation (ERR-0010): a
target-bank/pending-bank race in memory_manager.v's activation-cache
wiring (the same bug class ERR-0006 already fixed once for
pf_target_bank - a later handoff's queued request can overwrite which
bank an earlier, still-in-flight request's ack applies to), and a
repeat of ERR-0009's N_SLOTS=1 zero-width replication bug in
activation_cache.v itself.

Real, measured results: the full final-benchmark campaign (24/24
workload/config combinations) re-verified bit-exact. D-Stress cycles
fall a further 1.66-2.00x on top of DEC-0015 (~4x combined vs the
original byte-level baseline). But the cache's real Fmax cost is much
steeper than DEC-0015's own: N_SLOTS=2 (the recommended default,
DEC-0014) drops from 133.58 to 87.72 MHz (-34%, margin over 80MHz
shrinks from +67% to +9.7%), and N_SLOTS=4 drops to 65.01 MHz - now
FAILING the 80MHz target it previously passed. Combined real
wall-clock speedup vs the original baseline: N=1 3.86x, N=2 2.45x
(both real net wins); N=4 is a real regression once its own now-failing
Fmax is honestly used, though N=4 was never the recommended
configuration.

N_SLOTS=2 remains the recommended default (DEC-0014 unaffected) with
a thinner but still real Fmax margin. Cache hit-detection pipelining
is flagged as concrete follow-up work if N_SLOTS>2 is ever needed with
the cache active - not attempted this round.

Logged: simulation/synthesis/timing/benchmark/decisions (DEC-0016)/
experiments (EXP-0016)/errors (ERR-0010)/development.log, ROADMAP.md
updated.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013xXuuRUWZScuo1DeYJxs3v
2026-09-05 20:59:14 +02:00

153 lines
7.3 KiB
Verilog

`timescale 1ns/1ps
// ================================================================
// FPGA-Neural V2 -- Neural Multiprocessor top (M8, docs/v2-description.md
// §15/§16: "Integrare il controller V1 senza modificarlo inizialmente.
// Misurare il comportamento reale.")
//
// The real, hardware-facing top-level: dataflow_core.v (M7) with its
// N_SLOTS independent Memory Backend Interface ports funneled through
// a new generic arbiter (slot_mem_arbiter.v, M8) down to the REAL,
// UNMODIFIED hardware/v1 PSRAM backend chain -- exactly the chain
// hardware/v2/sim/tb_memory_manager.v (M4) already proved correct for
// ONE memory_manager port. This module is the first point M3 (per
// DEC-0009) and M2 (per DEC-0006) BOTH deferred to: N_SLOTS
// memory_manager instances genuinely sharing one physical PSRAM port.
//
// Post-M10 (decisions.log DEC-0015): the chain is now
// memory_interface -> psram_controller
// -- int8_memory_access.v is no longer instantiated here.
// int8_memory_access itself is untouched (still frozen V1, §1/§34);
// V2 simply reuses the lower (word-level) layer of the same frozen
// chain directly, since prefetch_engine.v/memory_manager.v now speak
// memory_interface's own 16-bit word protocol natively (see those
// modules' headers for why: every real transaction now moves a full
// PSRAM word instead of discarding half of it, halving the number of
// real backend round-trips per tile fetch).
//
// dataflow_core.v itself is NOT modified in its own control logic --
// its per-slot interface (DEC-0009) is exactly what makes it pluggable
// into an arbiter here without touching M7's own file (only the
// WIDTH of that per-slot interface changed, from 8 to 16 bits plus
// lb_n/ub_n, a mechanical consequence of DEC-0015, not a redesign of
// dataflow_core's own scheduling/dependency logic).
// ================================================================
module neural_multiprocessor #(
parameter DATA_WIDTH = 8,
parameter P_IN = 8,
parameter ACC_WIDTH = 32,
parameter ADDR_WIDTH = 23,
parameter N_SLOTS = 4,
parameter N_NODES = 16,
parameter MAX_DEPS = 4,
parameter QUEUE_DEPTH = 8,
parameter PSRAM_DATA_WIDTH = 16,
parameter CLK_FREQ_MHZ = 80
)(
input wire clk,
input wire rst,
// ---- node registration (host / graph loader -> Dependency Manager) ----
input wire reg_valid,
output wire reg_ready,
input wire [$clog2(N_NODES)-1:0] reg_node_id,
input wire [$clog2(MAX_DEPS+1)-1:0] reg_required,
input wire [MAX_DEPS*$clog2(N_NODES)-1:0] reg_producer_ids,
input wire [ADDR_WIDTH-1:0] reg_x_base,
input wire [ADDR_WIDTH-1:0] reg_w_base,
input wire [15:0] reg_n_tiles,
input wire [ADDR_WIDTH-1:0] reg_result_addr,
// ---- real PSRAM pins (hardware/v1/rtl/psram_controller.v's own
// contract, unmodified) ----
output wire [ADDR_WIDTH-1:0] psram_a,
inout wire [PSRAM_DATA_WIDTH-1:0] psram_dq,
output wire psram_ce_n,
output wire psram_oe_n,
output wire psram_we_n,
output wire psram_lb_n,
output wire psram_ub_n,
output wire psram_zz_n
);
// ---- dataflow_core (M7, control logic unmodified; per-slot
// backend port widened to 16-bit + lb_n/ub_n per DEC-0015, and to
// N_SLOTS+1 ports per DEC-0016 -- the extra port is the shared
// activation_cache's own backend traffic) ----
wire [N_SLOTS:0] slot_mem_req, slot_mem_wr;
wire [ADDR_WIDTH*(N_SLOTS+1)-1:0] slot_mem_addr;
wire [16*(N_SLOTS+1)-1:0] slot_mem_wdata, slot_mem_rdata;
wire [N_SLOTS:0] slot_mem_lb_n, slot_mem_ub_n;
wire [N_SLOTS:0] slot_mem_ready;
dataflow_core #(
.DATA_WIDTH(DATA_WIDTH), .P_IN(P_IN), .ACC_WIDTH(ACC_WIDTH), .ADDR_WIDTH(ADDR_WIDTH),
.N_SLOTS(N_SLOTS), .N_NODES(N_NODES), .MAX_DEPS(MAX_DEPS), .QUEUE_DEPTH(QUEUE_DEPTH)
) u_dataflow_core (
.clk(clk), .rst(rst),
.reg_valid(reg_valid), .reg_ready(reg_ready), .reg_node_id(reg_node_id),
.reg_required(reg_required), .reg_producer_ids(reg_producer_ids),
.reg_x_base(reg_x_base), .reg_w_base(reg_w_base), .reg_n_tiles(reg_n_tiles),
.reg_result_addr(reg_result_addr),
.slot_mem_req(slot_mem_req), .slot_mem_wr(slot_mem_wr), .slot_mem_addr(slot_mem_addr),
.slot_mem_wdata(slot_mem_wdata), .slot_mem_lb_n(slot_mem_lb_n), .slot_mem_ub_n(slot_mem_ub_n),
.slot_mem_rdata(slot_mem_rdata), .slot_mem_ready(slot_mem_ready)
);
// ---- (N_SLOTS+1) -> 1 arbiter (M8, word-level per DEC-0015;
// widened to N_SLOTS+1 ports per DEC-0016 to also arbitrate the
// shared activation_cache's own backend traffic) ----
wire arb_m_req, arb_m_wr;
wire [ADDR_WIDTH-1:0] arb_m_addr;
wire [15:0] arb_m_wdata;
wire arb_m_lb_n, arb_m_ub_n;
wire [15:0] arb_m_rdata;
wire arb_m_ready;
slot_mem_arbiter #(
.ADDR_WIDTH(ADDR_WIDTH), .N_PORTS(N_SLOTS+1)
) u_arbiter (
.clk(clk), .rst(rst),
.s_req(slot_mem_req), .s_wr(slot_mem_wr), .s_addr(slot_mem_addr),
.s_wdata(slot_mem_wdata), .s_lb_n(slot_mem_lb_n), .s_ub_n(slot_mem_ub_n),
.s_rdata(slot_mem_rdata), .s_ready(slot_mem_ready),
.m_req(arb_m_req), .m_wr(arb_m_wr), .m_addr(arb_m_addr), .m_wdata(arb_m_wdata),
.m_lb_n(arb_m_lb_n), .m_ub_n(arb_m_ub_n),
.m_rdata(arb_m_rdata), .m_ready(arb_m_ready)
);
// ---- real, unmodified V1 PSRAM backend chain (memory_interface
// -> psram_controller; int8_memory_access no longer in this
// datapath -- see file header, DEC-0015) ----
wire pc_mem_req, pc_mem_wr;
wire [ADDR_WIDTH-1:0] pc_mem_addr;
wire [PSRAM_DATA_WIDTH-1:0] pc_mem_wdata;
wire pc_mem_lb_n, pc_mem_ub_n;
wire [PSRAM_DATA_WIDTH-1:0] pc_mem_rdata;
wire pc_mem_ready;
memory_interface #(.ADDR_WIDTH(ADDR_WIDTH), .DATA_WIDTH(PSRAM_DATA_WIDTH)) u_memif (
.clk(clk), .rst(rst),
.req(arb_m_req), .wr(arb_m_wr), .addr(arb_m_addr), .wdata(arb_m_wdata),
.lb_n(arb_m_lb_n), .ub_n(arb_m_ub_n),
.rdata(arb_m_rdata), .ready(arb_m_ready),
.mem_req(pc_mem_req), .mem_wr(pc_mem_wr), .mem_addr(pc_mem_addr), .mem_wdata(pc_mem_wdata),
.mem_lb_n(pc_mem_lb_n), .mem_ub_n(pc_mem_ub_n),
.mem_rdata(pc_mem_rdata), .mem_ready(pc_mem_ready)
);
psram_controller #(
.ADDR_WIDTH(ADDR_WIDTH), .DATA_WIDTH(PSRAM_DATA_WIDTH), .CLK_FREQ_MHZ(CLK_FREQ_MHZ)
) u_psram_ctrl (
.clk(clk), .rst(rst),
.mem_req(pc_mem_req), .mem_wr(pc_mem_wr), .mem_addr(pc_mem_addr), .mem_wdata(pc_mem_wdata),
.mem_lb_n(pc_mem_lb_n), .mem_ub_n(pc_mem_ub_n),
.mem_rdata(pc_mem_rdata), .mem_ready(pc_mem_ready),
.psram_a(psram_a), .psram_dq(psram_dq),
.psram_ce_n(psram_ce_n), .psram_oe_n(psram_oe_n), .psram_we_n(psram_we_n),
.psram_lb_n(psram_lb_n), .psram_ub_n(psram_ub_n), .psram_zz_n(psram_zz_n)
);
endmodule