Lot 01 · ALU · Historical

The 270 millimetre predecessor — complete on paper, set aside for copper.

Before Tomato’s dual-LUT pivot, there was alu.tmarhguy.com: an 8-bit hybrid ALU from 3,488 discrete MOSFETs on a monolithic 270×270 mm board.

270 × 270 mm · 19 operations · 5 flags · pure combinational

This lot is the origin story—not the board that went to JLCPCB. It proved the narrative: a full ALU you could hold, with a custom graphics block in the bottom-left corner, power-hungry and proud. Manufacturing costs on a dorm-room budget forced the pivot to 74xx dual-LUT slices (07_alu). The idea survived; the 270 mm outline did not.

Functional blocks

Arithmetic (top-left): 8× 1-bit full adders, XOR array for B, carry chain — A + B or A − B via 2’s complement.

Logic (top-right): NAND, NOR, XOR, PASS A/B through a 5:1 mux bank.

Selection (center): 2:1 mux between arithmetic and logic, global inverter.

Flags (bottom-left): EQUAL, LESS, POSITIVE, COUT — same quadrant philosophy as the successor board’s flag sheet.

Control (bottom-right): FUNC[4:0] → M, MUX_SEL, INV_OUT, LOGIC_SEL — combinational decode, no clock.

Outline: 270 × 270 mm = 72,900 mm²
Density: 436 T/bit · ≈9112 mm²/bit
Delay: ~445 ns worst case
Power: 5 V · 0.5–1 A · <200 mA idle bring-up
Status: Design complete · superseded by 07

Four-bit ALU slice schematic — origin of the Tomato datapath. — Fig. — 4-bit slicePaper authority · lot 01

The live predecessor site still documents bench photos, operations, and the transistor romance: alu.tmarhguy.com.