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Budget both profiles against both clocks: the CPU limit is the clock, not the profile

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11_cpu_budget.py takes --machine. Clocks confirmed from MAME 0.277
x68k.cpp:1133/1194/1200, not recalled: x68000 AND x68ksupr are both
40_MHz_XTAL/4 = 10 MHz; only the XVI is faster at 33.33_MHz_XTAL/2.

                sasi            scsi
  stock 10MHz   31% miss        42% miss
  XVI 16.7MHz   0% miss         0% miss

sasi is the cheaper profile but it does not fit either at 10 MHz. The XVI
column is headroom, not a target: the profiles are an I/O-bandwidth axis and
say nothing about CPU, and the locked target CPU is a stock 10 MHz 68000 for
both of them. So both profiles have to fit the same 833,333-cycle budget, and
the cycle ceiling has to be enforced in the encoder regardless of which one
ships.

Model comparisons are now gated to the clock and framerate they were stated
at: quoting 24.5's 76.6% or the stock-machine 68000 timings against an XVI
budget compares a model to a measurement of a different machine.

Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
This commit is contained in:
prosolis
2026-08-23 15:13:34 -07:00
parent e1aa26bb57
commit ed353d24a9
1 changed files with 34 additions and 11 deletions
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tools/analysis/11_cpu_budget.py
+31 -8
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@@ -23,9 +23,12 @@ sys.path.insert(0, "tools/encoder")
import numpy as np
from dlx import DLX
CPUHZ = 10_000_000
# Machine clocks, confirmed from MAME 0.277 src/mame/sharp/x68k.cpp:1133/1194/
# 1200 -- not recalled. x68000 and x68ksupr are BOTH 40_MHz_XTAL/4 = 10 MHz;
# only the XVI is faster, at 33.33_MHz_XTAL/2. So "has SCSI" and "has a faster
# CPU" are different sets of machines: the Super has SCSI at 10 MHz.
CLOCKS = {"stock": 10.0, "super": 10.0, "xvi": 33.33 / 2, "x68030": 25.0}
FPS = 12
FRAME = CPUHZ / FPS # 833,333 cycles
# cycles per block, measured on the emulated 68000 (synthetic single-mode frames)
C_V1, C_V4, C_RAW = 299.9, 448.2, 400.4
@@ -35,7 +38,13 @@ C_SKIP_MIXED = 45.0 # a SKIP block inside a mixed byte
ap = argparse.ArgumentParser()
ap.add_argument("container", nargs="?",
default="tmp/rc_fr_singe_sasi_rcprofile.dlx")
ap.add_argument("--machine", default="stock", choices=list(CLOCKS),
help="which X68000's clock to budget against (default stock)")
ap.add_argument("--fps", type=float, default=FPS)
a = ap.parse_args()
CPUHZ = CLOCKS[a.machine] * 1e6
FPS = a.fps
FRAME = CPUHZ / FPS
if not os.path.exists(a.container):
sys.exit(f"missing {a.container}")
@@ -58,6 +67,13 @@ pct = 100 * cyc / FRAME
ns = np.array([100 * (m != 0).mean() for m in modes])
print(f"{a.container}: {d.nframes} frames, {d.nb} blocks/frame")
print(f"budget: {a.machine} @ {CLOCKS[a.machine]:.2f} MHz, {FPS:g} fps "
f"-> {FRAME:,.0f} cycles/frame")
if a.machine != "stock":
print(" (derived: scaled by clock from cycles measured on the 10 MHz core.\n"
" MAME 0.277 marks x68ksupr/x68kxvi/x68030 MACHINE_NOT_WORKING, so\n"
" this is not measured on those machines and ignores any difference\n"
" in memory timing.)")
print(f"measured block costs: SKIP {C_SKIP_FAST*4:.0f}/4 (clustered) "
f"{C_SKIP_MIXED:.0f} (mixed) V1 {C_V1:.0f} V4 {C_V4:.0f} RAW {C_RAW:.0f} cycles\n")
@@ -67,27 +83,34 @@ print(f"measured block costs: SKIP {C_SKIP_FAST*4:.0f}/4 (clustered) "
TIMED = "tmp/rc_fr_singe_sasi_rcprofile.dlx"
TIMED_FRAMES = (("min non-SKIP", 15.4, 31.5), ("median", 48.1, 73.8),
("p90", 82.5, 116.4), ("max non-SKIP", 100.0, 135.8))
if os.path.abspath(a.container) == os.path.abspath(TIMED):
if (os.path.abspath(a.container) == os.path.abspath(TIMED)
and a.machine == "stock" and a.fps == 12):
print("model vs the frames actually timed on the 68000:")
for label, frac, meas in TIMED_FRAMES:
i = int(np.argmin(abs(ns - frac)))
print(f" {label:<14} non-SKIP {ns[i]:5.1f}% model {pct[i]:6.1f}% "
f"measured {meas:5.1f}% error {pct[i]-meas:+.1f} pt")
else:
print(f"(no 68000 timings for this container -- the model was validated to "
f"within\n 1 pt on {TIMED}; run tools/bench/decode.lua to time this one)")
print(f"(no 68000 timings for this container/machine -- the model was "
f"validated to\n within 1 pt on {TIMED} at stock/12fps;\n"
f" run tools/bench/decode.lua to time another container)")
old = 76.6 * ns / 100
print(f"\nper-frame cost, % of a {FPS}fps frame budget:")
print(f"\nper-frame cost, % of a {FPS:g}fps frame budget:")
print(f" measured-cost model: median {np.median(pct):5.1f} "
f"p90 {np.percentile(pct,90):5.1f} max {pct.max():5.1f}")
if a.machine == "stock" and a.fps == 12:
# 24.5's 76.6% is a 10 MHz / 12 fps figure; quoting it at another clock or
# framerate would be comparing against a model that was never stated there.
old = 76.6 * ns / 100
print(f" FINDINGS 24.5 model: median {np.median(old):5.1f} "
f"p90 {np.percentile(old,90):5.1f} max {old.max():5.1f} "
f"(optimistic by {np.median(pct)/np.median(old):.2f}x at the median)")
miss = pct > 100
print(f"\nframes that do NOT fit 833,333 cycles: {miss.sum()}/{d.nframes} "
print(f"\nframes that do NOT fit {FRAME:,.0f} cycles: {miss.sum()}/{d.nframes} "
f"({100*miss.mean():.0f}%)")
print(f" sustainable framerate if EVERY frame must fit: "
f"{CPUHZ/cyc.max():.1f} fps; at the mean frame {CPUHZ/cyc.mean():.1f} fps")
if miss.any():
print(f" worst {pct.max():.1f}% -- {(pct.max()-100)/100*1000/FPS:.0f} ms late "
f"on an {1000/FPS:.0f} ms frame")