KRkristianpaul·Oct 8, 2026Submission
1 points · Open discussionolofk
serv
Verilog2019–2026
olofk / serv
serv
SERV - The SErial RISC-V CPU
24Distinct people
27Mentions
0Explicit recommenders
1.9KGitHub stars
What to know before exploring
What it is
SERV - The SErial RISC-V CPU
GitHub
Where it is used
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What people are saying
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Also in these discussions
- yosyshq/picorv32 · linked in 3 of the same discussions
Mentioned in the same Hacker News threads. That is not proof they are substitutes.
This week on Hacker News
Nov 7–Nov 14 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/14/2026, 3:03:16 PM UTC.
No direct repository links were found in the indexed HN discussions over the past seven days. Older discussions are available below.
Mentions over time
HN mentions by year27 dated mentions
Observed mentions: 2019-08-14 14:26:27 UTC to 2026-10-08 02:27:55 UTC.
* An incomplete calendar period is marked with an outlined bar. Its count is not directly comparable with a full period.
Counts come from the repository’s dated source evidence. Index cutoff: 2026-11-02 08:16:59 UTC.
View mention counts and date ranges
| Period | Start (UTC) | End (exclusive, UTC) | Mentions | Submissions | Comments |
|---|---|---|---|---|---|
| 2019 | 2019-01-01 00:00:00 UTC | 2020-01-01 00:00:00 UTC | 1 | 0 | 1 |
| 2020 | 2020-01-01 00:00:00 UTC | 2021-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2021 | 2021-01-01 00:00:00 UTC | 2022-01-01 00:00:00 UTC | 3 | 0 | 3 |
| 2022 | 2022-01-01 00:00:00 UTC | 2023-01-01 00:00:00 UTC | 5 | 0 | 5 |
| 2023 | 2023-01-01 00:00:00 UTC | 2024-01-01 00:00:00 UTC | 5 | 3 | 2 |
| 2024 | 2024-01-01 00:00:00 UTC | 2025-01-01 00:00:00 UTC | 6 | 1 | 5 |
| 2025 | 2025-01-01 00:00:00 UTC | 2026-01-01 00:00:00 UTC | 2 | 0 | 2 |
| 2026 (partial) | 2026-01-01 00:00:00 UTC | 2027-01-01 00:00:00 UTC | 3 | 2 | 1 |
What Hacker News says
27 sourcesSERV – The SErial RISC-V CPU Topics
3 points · Open discussionNote, if you need a barebones CPU but want to save on gates, you can go with a serial (1-bit) CPU, e.g. SERV which only takes up 198 LUTs on ice40,[1] leaving plenty of space to do other things.
[1] https://github.com/olofk/serv
In WebFPGAThanks to the Archive.org link, we can see that indeed they link directly to the SERV github in reference 38:
38. Kindgren, O. et al. SERV - The SErial RISC-V CPU. GitHub http:/github.com/olofk/serv (2020).
In A 32-bit processor made with an atomically thin semiconductorI suspected that this was the case when they mentioned adding "one bit at a time" -- the CPU design that they implemented is Olof Kindgren's SERV [0], a tiny bit-serial risc-v CPU/soc (award-winning, of course).
From [1]:
> Olof Kindgren
> 5th April 2025 at 10:59 am
> It’s a great achievement, but I’m of course a little sad to see that it’s not mentioned anywhere that Wuji is just a renaming of my CPU, SERV. They even pasted in block diagrams from my documentation.
[0] https://github.com/olofk/serv
[1] https://www.electronicsweekly.com/news/business/2d-32-bit-ri...
In A 32-bit processor made with an atomically thin semiconductorThey are spot-on with the transistor count for the CPU (though I believe it doesn't include all your RAM registers). SERV is a serial CPU that can range from doing calculations just 1 bit at a time up to doing them 4 bits at a time.
https://github.com/olofk/serv
It's pretty incredible considering the 6502 was already considered tiny when it was released with just ~4500 gates vs the 6500 in the 8085 and the 8500 in the z80.
In A Bendy RISC-V ProcessorFor those who don't know SERV is a serial RISC-V architecture - really small, fits in a Tiny Tapeout tile
https://github.com/olofk/serv
In A Bendy RISC-V Processor> The research team found Flex-RV could run as fast as 60 kilohertz while consuming less than 6 milliwatts of power.
They don’t give all details, but I think it’s safe to say there’s work to do w.r.t. performance/Watt, probably more so given that the CPU seems to be bit serial (https://github.com/olofk/serv), which I think means an addition takes 32 cycles.
In Flexible RISC-V Processor: Could Cost Less Than a Dollari just learned the other day that you can get a computer for 1.58¢ in quantity 20000: https://jlcpcb.com/partdetail/NyquestTech-NY8A051H/C5143390
if we can believe the datasheet, it's basically a pic12f clone (with 55 'powerful' instructions, most single-cycle) with 512 instructions of memory, a 4-level hardware stack, and 32 bytes of ram, with an internal 20 megahertz clock, 20 milliamps per pin at 5 volts, burning half a microamp in halt mode and 700 microamps at full speed at 3 volts
and it costs less than most discrete transistors. in fact, although that page is the sop-8 version, you can get it in a sot23-6 package too
there are definitely a lot of things you can do with this chip if you're willing to optimize your code. but you aren't going to start with a 30-kilobyte firmware image and optimize it until it fits
yeah it's not an n
Read the rest
rf52840 and you probably can't do ble on it. but the ny8a051h costs 1.58¢, and an nrf52840 costs 245¢, 154 times as much, and only runs three times as fast on the kinds of things you'd mostly use the ny8a051h for. it does have a lot more than 154 times as much ram tho
for 11.83¢ you can get a ch32v003 https://www.lcsc.com/product-detail/Microcontroller-Units-MC... which is a 48 megahertz risc-v processor with 2 kilobytes of ram, 16 kilobytes of flash, a 10-bit 1.7 megahertz adc, and an on-chip op-amp. so for 5% of the cost of the nrf52840 you get 50% of the cpu speed, 1.6% of the ram, and 0% of the bluetooth
for 70¢, less than a third the price of the nrf52840, you can get an ice40ul-640 https://www.lcsc.com/product-detail/Programmable-Logic-Devic... which i'm pretty sure can do bluetooth. though it might be saner to hook it up to one of the microcontrollers mentioned above (or maybe something with a few more pins), you can probably fit olof kindgren's serv implementation of risc-v https://github.com/olofk/serv into about a third of it and probably get over a mips out of it. but the total amount of block ram is 7 kilobytes. the compensating virtue is that you have another 400 or so luts and flip-flops to do certain kinds of data processing a lot faster and more predictably than a cpu can. 19 billion bit operations per second and pin-to-pin latency of 9 nanoseconds
so my summary is that there's a lot of that kind of embedded work going on, maybe more than ever, and you can do things today that were impossible only a few years ago
> Right now, most devices on the market do not support the C extension
This is not true and easily verifiable.
The C extension is defacto required, the only cores that don't support it are special purpose soft cores.
C extension in the smallest IP available core https://github.com/olofk/serv?tab=readme-ov-file
Supports M and C extensions https://github.com/YosysHQ/picorv32
Another sized optimized core with C extension support https://github.com/lowrisc/ibex
C extension in the 10 cent microcontroller https://www.wch-ic.com/products/CH32V003.html
This one should get your goat, it implements as much as it can using only compressed instructions https://github.com/gsmecher/minimax
In RISC-V support in Android just got a big setback>anybody knows if such a mini board with plenty of GPIOs and usb-c (device/host/board power) and a risc-v MCU, but 64bits, does exists?
Something like the Milk-V Duo[0]?
More options in this nice list[1].
>(This would be for a 100% 64bits risc-v assembly keyboard firmware).
I would go with a small FPGA (iCE40 e.g. LP640 or LP1K, or GW1N) and SERV[2].
0. https://milkv.io/duo
1. https://codeberg.org/20-100/Awesome_RISC-V/src/branch/master...
2. https://github.com/olofk/serv
In Linux on RISC-V on Arduino UnoSERV: A bit-serial RISC-V core
9 points · Open discussionSERV – open-source Tiny SErial RISC-V CPU
3 points · Open discussionShowing the 15 most recent of 27 sources. Enable JavaScript to search and browse every indexed mention.