https://tmarhguy.com/writing/ Writing on hardware projects by Tyrone Marhguy. en-us Mon, 03 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-03-reassessing-mac-for-optimization/ Returning to the MAC tapeout path after months on Tomato — planning LibreLane flow, cross-verification, and timing closure. 16-bit MAC Unit (Sky130) Mon, 03 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-03-reassessing-mac-for-optimization/ https://tmarhguy.com/writing/2026-08-02-designing-additional-boards/ I am pushing to design the remaining boards. I had assumed that the most complicated one to design was the main board — the ALU — which is done and routed (07_alu). The next thi... Tomato CPU Sun, 02 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-02-designing-additional-boards/ https://tmarhguy.com/writing/2026-08-02-successful-synthesis-implementation-bitstream/ First clean Vivado build for the Nexys A7 ITCH pipeline — synthesis, implementation, and bitstream with USE_ETH=1. NASDAQ ITCH Hardware Parser Sun, 02 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-02-successful-synthesis-implementation-bitstream/ https://tmarhguy.com/writing/2026-08-01-itch-ethernet-lab-bring-up/ Preparing Nexys A7 Ethernet ingress for end-to-end Mold/ITCH UDP testing on the FPGA market-data pipeline. NASDAQ ITCH Hardware Parser Sat, 01 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-01-itch-ethernet-lab-bring-up/ https://tmarhguy.com/writing/2026-08-01-shell-ui-mango/ As the toolkit expands, remembering individual script paths, names, and arguments becomes cumbersome. To solve this, I am introducing Mango—a centralized, interactive shell inte... Mango Tools Sat, 01 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-01-shell-ui-mango/ https://tmarhguy.com/writing/2026-08-01-tools/ This project is a centralized, offline repository designed to replace SaaS platforms (like iLovePDF and online image compressors) entirely. By housing my most frequently used ut... Mango Tools Sat, 01 Aug 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-08-01-tools/ https://tmarhguy.com/writing/2026-07-31-falling-back-to-32b/ In a rather if not seemingly swing between implementations, I have reconsidered and am falling back to the 32b design. The 40b redesign was intellectually clean — one word type,... Tomato CPU Fri, 31 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-31-falling-back-to-32b/ https://tmarhguy.com/writing/2026-07-31-the-lingering-thoughts/ The ALU is routed and ready for PCB fabrication. That was the hardest slice of the datapath — three-operand LUT3, carry select, the full combinational core. The lingering proble... Tomato CPU Fri, 31 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-31-the-lingering-thoughts/ https://tmarhguy.com/writing/2026-07-30-redesign-into-40b-old-design-32b/ After roughly three months working on Tomato32, the recurring bottleneck has been instruction width, not the ALU itself. Convention says a 32-bit machine gets a 32-bit instructi... Tomato CPU Thu, 30 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-30-redesign-into-40b-old-design-32b/ https://tmarhguy.com/writing/2026-07-13-architecture-upgrade/ The sheer constraint posed by area and available hardware imply that designs that offer more for less are favourable, unlike conventional metrics like parasitic and wiring budge... Tomato CPU Mon, 13 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-13-architecture-upgrade/ https://tmarhguy.com/writing/2026-07-13-demo-ideas/ It quickly gets abstracted and perhaps indistinguishable from a black box if the final design has no reasonably impressive demo. I've considered a lot of ideas ranging from mode... Tomato CPU Mon, 13 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-13-demo-ideas/ https://tmarhguy.com/writing/2026-07-13-downgrade-for-an-upgrade-32b-to-16b-x-4/ This ALU has taken several routes since the first abstractions. In the most recent version before this change, I wanted to wire 8 cells of 4b each into a 32b cell. The catch is ... Tomato CPU Mon, 13 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-13-downgrade-for-an-upgrade-32b-to-16b-x-4/ https://tmarhguy.com/writing/2026-07-13-pipelined-fpga-what-if/ After observing, time is but a monotonic quantity and universal. In current FPGA designs, we program and use, and for another use case, we repeat, In future tomato designs, I am... Tomato CPU Mon, 13 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-13-pipelined-fpga-what-if/ https://tmarhguy.com/writing/2026-07-13-truth-table-latch/ In the current design, the individual cells of tomato may not seem to undergo reprogramming for each operation, given the philosophy it was based off of: what if computers had t... Tomato CPU Mon, 13 Jul 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-07-13-truth-table-latch/ https://tmarhguy.com/writing/2026-06-27-elimination-of-mode-multiplexers/ Initial State & Bottleneck: The previous ALU design utilized a parallel execution model. An incoming signal would split: one path raced through the A/B masking logic into the 74... Tomato CPU Sat, 27 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-27-elimination-of-mode-multiplexers/ https://tmarhguy.com/writing/2026-06-26-alu-architecture-refinement-logic-optimization/ Refinement of Generate ($G$) and Propagate ($P$) Signals In the initial architecture, the logic generation for the 74182 look-ahead unit was bottlenecked by a naïve implementati... 8-bit Discrete Transistor ALU Fri, 26 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-26-alu-architecture-refinement-logic-optimization/ https://tmarhguy.com/writing/2026-06-26-alu-redesign-with-74251/ In routing the ALU, I came across a realization that the fact that the 125 + 138 combination defeats the optimization i was looking for. In fact, I need 3 chips for a single ALU... 8-bit Discrete Transistor ALU Fri, 26 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-26-alu-redesign-with-74251/ https://tmarhguy.com/writing/2026-06-19-alu-segment-display-design/ Four 32-bit values on screen at once—the three LUT3 operand buses plus the ALU writeback. Each row is eight hex digits; thirty-two seven-segment displays total, live as the data... 8-bit Discrete Transistor ALU Fri, 19 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-19-alu-segment-display-design/ https://tmarhguy.com/writing/2026-06-16-microcode-control-modularization/ The microcode ROM was always going to be a wiring problem. Every instruction looks up a 64-bit control word: what the ALU should do, whether to write a register, read memory, ju... Tomato CPU Tue, 16 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-16-microcode-control-modularization/ https://tmarhguy.com/writing/2026-06-15-multiplication-and-division/ One of the biggest hurdles in this build has been implementing hardware multiplication and division. The standard naive approach—sequencing operations to `shift -> add -> accumu... Tomato CPU Mon, 15 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-15-multiplication-and-division/ https://tmarhguy.com/writing/2026-06-11-load-store-pipeline-analysis/ Every opcode indexes a 48-bit word in the microcode ROM (`DIG_ROM_256X48_microcodeeeprom`). The fields, confirmed from `main.v:2087–2106`: | Bits | Field | Notes | |------|-----... Tomato CPU Thu, 11 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-11-load-store-pipeline-analysis/ https://tmarhguy.com/writing/2026-06-10-implementing-mul-div-engine/ Today's goal is integrating the multiply-divide engine. I am considering a few ideas. 74xx284/85 can compute the lower and upper products, so I will use them and sequence to com... Tomato CPU Wed, 10 Jun 2026 12:00:00 GMT https://tmarhguy.com/writing/2026-06-10-implementing-mul-div-engine/ https://tmarhguy.com/writing/welcome-to-tomato-32/ This is a build log for Tomato 32. It will keep track of the questions that come up and the answers I settled for. It focussed on build log, the constraints explored and the jou... Tomato CPU Fri, 01 Aug 2025 12:00:00 GMT https://tmarhguy.com/writing/welcome-to-tomato-32/