Category Archives: cpu

Relay Computer: You Can Hear It Think

Modern digital computers have complex instruction sets that runs on state-of-the-art ALUs which in turn are a consequence of miniaturized logic gates that are built with tiny transistors. These tiny transistors are essentially switches. You could imagine replacing with electromagnetic relays, and get what is called a relay computer. If you can imagine it, someone’s done it. In this case, [jhallenworld].

The Z3 was the first working programmable, fully automatic digital computer designed by Konrad Zuse. The board employs modern semiconductor devices such as memory and microcontrollers, however, the CPU is all relays. A hexadecimal keyboard allows for program entry …read more

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Posted in classic hacks, computer, Computer Hacks, cpu, discrete, relay, relay computer | Leave a comment

You Know You Can Do That with a 555

Hardly a week goes by that we don’t post a project where at least one commenter will lament that the hacker could have just used a 555. [Peter Monta] clearly gets that point of view. For a 555 design contest, he created both digital logic gates and an op amp, all using 555 chips. We can’t quite imagine the post apocalyptic world where the only surviving electronic components are 555 chips, but if that day were to come, [Peter] is your guy.

Using the internal structure of the 555, [Peter] formed a basic logic gate, an inverter, latches, and more. …read more

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Posted in counter, cpu, logic gate, misc hacks, op-amp | Leave a comment

Find Instructions Hidden In Your CPU

There was a time when owning computer meant you probably knew most or all of the instructions it could execute. Your modern PC, though, has a lot of instructions, many of them meant for specialized operating system, encryption, or digital signal processing features.

There are known undocumented instructions in a lot of x86-class CPUs, too. What’s more, these days your x86 CPU might really be a virtual machine running on a different processor, or your CPU could have a defect or a bug. Maybe you want to run sandsifter–a program that searches for erroneous or undocumented instructions. Who knows what …read more

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Posted in cpu, instruction set architecture, intel, isa, software hacks, undocumented, undocumented instructions, x86 | Leave a comment

Virtual CPU Stays on Script

Some will see it as a great thing, and others as an example of how JavaScript is being abused daily, but [Francis Stokes] decided to design his own CPU architecture and implemented a virtual version of it using JavaScript. The CPU is a 16-bit affair and has a simplified assembly language. The code is on GitHub, but the real value is [Francis’] exposition of the design in the original post.

While discussing the design, [Francis] reveals his first pass at the instruction set, discussed what he found wrong about it, and then reveals the final set composed of real instructions …read more

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Posted in assembler, Computer Hacks, cpu, javascript | Leave a comment

VexRiscv: A Modular RISC-V Implementation for FPGA

Since an FPGA is just a sea of digital logic components on a chip, it isn’t uncommon to build a CPU using at least part of the FPGA’s circuitry. VexRiscv is an implementation of the RISC-V CPU architecture using a language called SpinalHDL.

SpinalHDL is a high-level language conceptually similar to Verilog or VHDL and can compile to Verilog or VHDL, so it should be compatible with most tool chains. VexRiscv shows off well in this project since it is very modular. You can add instructions, an MMU, JTAG debugging, caches and more.

When you build a CPU in FPGA, …read more

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Posted in cpu, custom cpu, FPGA, RISC-V, spinalhdl, verilog, vhdl | Leave a comment

Simulating the Learn-by-Fixing CPU

Last time I looked at a simple 16-bit RISC processor aimed at students. It needed a little help on documentation and had a missing file, but I managed to get it to simulate using a free online tool called EDA Playground. This time, I’ll take you through the code details and how to run the simulation.

You’ll want to refer to the previous post if you didn’t read it already. The diagrams and tables give a high-level overview that will help you understand the files discussed in this post.

If you wanted to actually program this on a real FPGA, …read more

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Posted in cpu, eda, eda playground, edaplayground, FPGA, Hackaday Columns, risc, simulation, Skills, verilog | Leave a comment

Learn by Fixing: Another Verilog CPU

Because I often work with students, I’m always on the look-out for a simple CPU, preferably in Verilog, in the Goldilocks zone. That is, not too easy and not too hard. I had high hopes for this 16-bit RISC processor presented by [fpga4student], but without some extra work, it probably isn’t usable for its intended purpose.

The CPU itself is pretty simple and fits on a fairly long web page. However, the details about it are a bit sparse. This isn’t always a bad thing. You can offer students too much help. Then again, you can also offer too little. …read more

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Posted in cpu, eda, eda playground, edaplayground, FPGA, Hackaday Columns, risc, Skills, verilog | Leave a comment

An 8-Bit Transport Triggered Architecture CPU in TTL

When we are introduced to the internals of a microprocessor, it is most likely that we will be shown something like one of the first generation of 8-bit CPUs from the 1970s. There will be the familiar group of registers and counters, an arithmetic and logic unit (ALU), and an instruction decoder with associated control logic. A complex instruction set causes the decoder to marshal registers and ALU to perform all the various functions in the right order. CPUs may have moved on in many ways since the 1970s, but the block diagram of an 8080 or similar still provides …read more

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Posted in Computer Hacks, cpu, homebrew cpu, transport triggered architecture, TTA, ttl | Leave a comment

iPhone Brain Surgery

You think you’re good at soldering? Can you solder a CPU? A CPU inside an iPhone? A decapped CPU inside an iPhone? Can you solder inside a decapped CPU inside of an iPhone?

If you can’t, fear not – someone can, and we found him or her courtesy of a video that [Bunnie Huang] tweeted a while back. There’s not much information in the video, but from what we can gather it comes from an outfit called G-Lon Technology in Guang Zhou. Their Facebook page suggests that they teach cellphone repair, and if they take their repairs this far, we’d …read more

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Posted in AP31, AR31, Cellphone Hacks, cpu, decapping, error 9, Iphone 6, iphone hacks, U301 | Leave a comment

FPGA Computer Covers A to Z

[F4HDK] calls his new computer A2Z because he built everything from scratch (literally, from A to Z). Well, strictly speaking, he did start with an FPGA, but you have to have some foundation. The core CPU is a 16-bit RISC processor with a 24-bit address bus and a 128-word cache. The computer sports 2 megabytes of RAM, a boot ROM, a VGA port and keyboard, and some other useful I/O. The CPU development uses Verilog.

Software-wise, the computer has a simple operating system, a filesystem, and basic programs like a text editor and an image viewer. Development software includes an …read more

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Posted in Computer Hacks, cpu, FPGA, vga | Leave a comment