Thousands Of Discrete MOSFETs Make Up This Compact CPU-Less Computer

May 19, 2021 by 19 Comments

How long has it been since a computer could boast about the fact that it contained 2,500 transistors? Probably close to half a century now, at a guess. So in a world with a couple of billion transistors per chip, is a 2,500-transistor computer really something to brag about? Yes. Yes, it is.

The CPU-less computer, called the TraNOR by its creator [Dennis Kuschel], is an elaboration on his previous MyNOR, another CPU-less machine that used a single NOR-gate made of discrete transistors as the core of its arithmetic-logic unit (ALU). Despite its architectural simplicity, MyNOR was capable of some pretty respectable performance, and even managed to play a decent game of Tetris. TraNOR, on the other hand, is much more complicated, mainly due to the fact that instead of relying on 74HC-series chips, [Dennis] built every single gate on the machine from discrete MOSFETs. The only chips on the four stacked PCBs are a trio of memory chips; we don’t fault him at all for the decision not to build the memory — he may be dedicated, but even art has its limits. And TraNOR is indeed a work of art — the video below shows the beautiful board layouts, with seemingly endless arrays of SMD transistors all neatly arranged and carefully soldered. And extra points for using Wintergatan’s marble machine melody as the soundtrack, too.

As much as we loved the original, TraNOR is really something special. Not only is it beautiful, but it’s functional — it’s even backward-compatible with MyNOR’s custom software. Hats off to [Dennis] for pulling off another wonderful build, and for sharing it with us.

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A CPU-Less Computer With A Single NOR-Gate ALU

November 23, 2020 by 13 Comments

We see a lot of discrete-logic computer builds these days, and we love them all. But after a while, they kind of all blend in with each other. So what’s the discrete logic aficionado to do if they want to stand out from the pack? Perhaps this CPU-less computer with a single NOR-gate instead of an arithmetic-logic unit is enough of a hacker flex? We certainly think so.

We must admit that when we first saw [Dennis Kuschel]’s “MyNor” we thought all the logic would be emulated by discrete NOR gates, which of course can be wired up in various combinations to produce every other logic gate. And while that would be really cool, [Dennis] chose another path. Sitting in the middle of the very nicely designed PCB is a small outcropping, a pair of discrete transistors and a single resistor. These form the NOR gate that is used, along with MyNor’s microcode, to perform all the operations normally done by the ALU.

While making the MyNor very slow, this has the advantage of not needing 74-series chips that are no longer manufactured, like the 74LS181 ALU. It may be slow, but as seen in the video below, with the help of a couple of add-on cards of similar architecture, it still manages to play Minesweeper and Tetris and acts as a decent calculator.

We really like the look of this build, and we congratulate [Dennis] on pulling it off. He has open-sourced everything, so feel free to build your own. Or, check out some of the other CPU-less computers we’ve featured: there’s the Gigatron, the Dis-Integrated 6502, or the jumper-wire jungle of this 8-bit CPU-less machine.

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The Smallest Homebrewed TTL CPU In The World

October 16, 2019 by 16 Comments

This may very well be the smallest homemade TTL CPU we’ve ever seen. Measuring at one square inch, this tiny chip boasts 40 connections, an 8-bit databus, a 16-bit address bus, a 64 kB memory space, reset and clock inputs, and 5 V power lines.

TTL (transistor transistor logic) logic chips are pretty outdated today, but they do have all of the basics necessary for building a computer – logic gates, counters, buffers, and registers. The transistors perform both the logic and amplifying, as compared to resistor-transistor logic (RTL) and diode-transistor logic (DTL). In the 60s, when the technology was still fairly new, TTL ICs were commonly used in computers and industrial controls. Even after the advent of VLSI, TTL ICs were still being used for interfacing more densely integrated chips. Even so, most TTL chips tend to be on the bulkier side, which is what makes [roelh]’s project so unique. The entire PCB is hardly any larger than a coin.

On top of the hardware specs, [roelh] also implemented several useful software features: zero page addressing, load/store/compare instructions, stacks, conditioning branching, subroutine calls, and memory-mapped I/O. The registers are also in RAM, which has been implemented in microprocessors in the past (see TMS9900) for speed considerations, but in this case was implemented for size constraints.

An ALU was also left out of the design in order to constrain its size, leaving only 8 ICs on either side of the 2-layer PCB.

Microprograms are stored in Flash memory and can be programmed with a Raspberry Pi. by saving the Assembly code to a memory card and downloading the assembled binary code. Once the Raspberry Pi is connected to the development board, you can burn the binary code onto the Flash memory of the board using a Python script. An online Javascript editor also exists for assembling the Assembly code for the chip and simulating the CPU.

There is currently a development board made for the CPU, which includes six seven-segment displays and an I/O connector for running a digital clock and other applications. [roelh] has since built a retro TTL computer around the chip, which reintroduces the ALU and includes address registers, 256 KB of RAM, VGA video, PS/2 keyboard port, a sound system, and I/O pins. It’s a really exciting project that’s seriously pushing the constraints of retro computing.

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Who Could Possibly Need An FPGA With 9M Logic Cells And 35B Transistors?

September 24, 2019 by 101 Comments

Xilinx recently announced the Virtex UltraScale+ VU19P FPGA. Of course, FPGA companies announce new chips every day. The reason this one caught our attention is the size of it: nearly 9 million logic cells and 35 billion transistors on a chip! If that’s not enough there is also over 2,000 user I/Os including transceivers that can move around 4.5 Tb/s back and forth.

To put things in perspective, the previous record holder — the Virtex Ultrascale 440 — has 5.5 million logic cells and an old-fashioned Spartan 3 topped out at about 50,000 cells — the new chip has about 180 times that capacity. For the record, I’ve built entire 32-bit CPUs on smaller Spartans.

That led us to wonder? Who’s buying these things? When I first heard about it I guessed that the price would be astronomical, partly due to expense but also partly because the market for these has to be pretty small. The previous biggest Xilinx part is listed on DigKey who pegs the Ultrascale 440 (an XCVU440-2FLGA2892E) at a cost of $55,000 as a non-stocked item. Remember, that chip has just over half the logic cells of the VU19P.

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The One-Transistor Flip-Flop

April 18, 2018 by 35 Comments

A flip-flop is one of the most basic digital electronic circuits. It can most easily be built from just two transistors, although they can and have been built out of vacuum tubes, NAND and NOR gates, and Minecraft redstone. Conventional wisdom says you can’t build a flip-flop with just one transistor, but here we are. [roelh] has built a flip-flop circuit using only one transistor and some bizarre logic that’s been slowly developing over on hackaday.io.

[roelh]’s single transistor flip-flop is heavily inspired by a few of the strange logic projects we’ve seen over the years. The weirdest, by far, is [Ted Yapo]’s Diode Clock, a digital clock made with diode-diode logic. This is the large-scale proof of concept for the unique family of logic circuits [Ted] came up with that only uses bog-standard diodes to construct arbitrary digital logic.

The single-transistor flip-flop works just like any other flip-flop — there are set and reset pulses, and a feedback loop to keep the whatever state the output is in alive. The key difference here is the addition of a clock signal. This clock, along with a few capacitors and a pair of diodes, give this single transistor the ability to store a single bit of information, just like any other flip-flop.

This is, without a doubt, a really, really weird circuit but falls well into territory that is easily understood despite being completely unfamiliar. The key question here is, ‘why?’. [roelh] says this could be used for homebrew CPUs, although this circuit is trading two transistors for a single transistor, two diodes, and a few more support components. For vacuum tube-based computation, this could be a very interesting idea that someone at IBM in the 40s had, then forgot to write down. Either way, it’s a clever application of diodes and an amazing expression of the creativity that can be found on a breadboard.

Programming The Open-V Open Source CPU On The Web

January 11, 2017 by 11 Comments

openriscv_webYou can now program the Open-V on the web, and see the results in real time. The code is compiled in the web IDE and then flashed to a microcontroller which is connected to a live YouTube live stream. It’s pretty neat to flash firmware on a microcontroller thousands of miles away and see the development board blink in response.

We’ve covered the Open-V before, and the crowd funding campaign they have going. The Open-V is an open hardware implementation of the RISC-V standard. And is designed to offer Cortex M0-class capabilities.

This feels like a create way to play around with some real hardware and get a taste of what a future where we can expect Arduino-like boards, open source down to the transistor level.

For a closer look at why open silicon matters, check out [Brian Benchoff’s] hands-on review of the HiFive, an Arduino form-factor board built around an open hardware RISC-V microcontroller.

One Bit, One Instruction Discrete CPU

November 30, 2016 by 26 Comments

There is a certain benefit to being an early adopter. If you were around when Unix or MSDOS had a handful of commands, it wasn’t hard to learn. Then you learn new things as they come along. If you started learning Linux or Windows today, there’s a huge number of details you have to tackle. You have the same problem trying to learn CPU design. Grappling with the design of a 16-bit CPU with a straightforward data path is hard enough. Throw in modern superscalar execution, pipelining, multiple levels of microcode, speculative execution, and all the other features modern processors have and you’ll quickly find yourself lost in the details.

[Michai Ramakers] wanted to build an educational CPU and he took a novel approach. The transistor CPU uses only one instruction and operates on one bit at a time. Naturally, this leads to a small data path, which is a good thing if you’re only using discrete transistors. His website is a ground-up tutorial in building and using the tiny computer.

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