I created it because I wanted my Nvidia GPUs to be compute only, and needed a cheap and small display GPU to run X11. I bought this GPU on AliExpress, after learning it had Linux support. It does, but kernel 5.x series and the sm750 driver in modern Linux only supports the older VGA/DVI variants.
Rather than send it back or throw it away, I decided to vibe code a new driver with new features, to make it usable for day to day desktop use. I've a little bit of a background in low level graphics so also added a cool little magic ordered dither (a pretty good one I think!) I devised myself, called "bbdither", and a few hacks to get 2560x1080 at 75hz on a device only officially documented as capable of up to 1920x1200 at 60hz, and PCI-E 1x speed.
Screenshots here: https://github.com/KodeMunkie/sm750hdmifb#screenshots
If you try it out, be careful - read the project disclaimer :)
*Vibe coded, as mentioned in Hackernews comments here https://news.ycombinator.com/item?id=49415282
That one is VGA so I think the original upstream driver should support it.
The unique bits I did do
- Checked the specs for actual hardware limits, DMA and any acceleration
- A magic dither based on my previous (normally coded) older projects (see GitHub)
- Image width "compression" idea with loss reduction using sharpening and a slight aspect change.
- Optimising DMA size chunking for optimal memory transfer.
- A lot of actual manual testing, including sheer reduction, frame rate testing, and multiple resolution and different monitor tests (and I lost one - the HDMI port no longer works on my old Celcus)
Failed experiments with:
- using the onboard secondary controller to bypass the primary controller limitations
- devising a hack that would use the vertical scan horizontally using monitor rotation
- attempting an 8, not 16/32 bit desktop for higher performance (old school technique).
- investigating non hardware hacks for overclocking the onboard chips.
- fixing a KVM issue, that required multiple physical disconnects and reconnects to replicate, and a significant amount of weekend time.
So yeah, vibe coded, because I'd never have been able to try these ideas in such a short timescale if I hadn't.
The words "I vibe coded this" explicitly disclaim any excess credit.
They did exactly what anyone can reasonably ask for. They exhibited essentially perfect integrity.
tldr; had Qwen orchestrate, do admin and assist with investigations, builds and debugging when codex was unavailable. Codex had a dedicated test physical machine, and I promoted the driver it created to the actual target (production) machine when it was stable enough. Used syncthing to keep the code synced between the different environments, with Qwen sending me progress updates on Telegram and querying Codex periodically.
Long answer:
1) Ran the concept and investigation past Qwen 3.6, I wanted a card that would fit my spare PCIe 3 X1 socket (faster cards in other sockets). Identified the sm750, and read up on its capabilities.
2) Due to speed and Qwen 3.6's capability, I handed Codex (on high) a whole physical scrap machine / fresh Mint install, with root access and the GPU directly connected and asked it what was needed. Syncthing copied the work folder to my machine desktop for visibility to my main orchestrating Qwen AI. Qwen could also ssh to the Codex owned machine to check progress and send me Telegram messages when any milestones were passed, as well as issues that might need me there.
3) I Identified all the chips on the sm750, whilst it was trying the official older sm750 drivers (attempting to get a HDMI signal) and gave them to it.
4) Used /plan mode to set the first iteration expectations, no DRM/integration into the control panel, modifying a checked out fbdev low level FB to test my magic dither algorithm (this can only be used for test, the integration needs to go elsewhere in the stack typically).
5) Left it a few hours, came back to see colour bars (success!)
6) Asked it to do the basic plumbing for X11, wondered how far I could push the frequencies past the VESA standards, fried the HDMI TV attempting high frequency modes (only realised next day I'd done this after the TV refused to activate that connector)
7) Plugged the card directly into the machine it would be used in, and the actual ultrawide monitor. Resumed the codex session on that machine, when daily limits were hit used Qwen 3.6/3.8 to package up builds, look for solutions to issues I was hitting. At this point the hardware is my "production" system, so effectively I've promoted test to staging.
8) From here I manually iterated with Codex by having it create scripts that would build the module for the current kernel to restart X11 with 1-3 ideas / fixes at a time.
9) In parallel, used Qwen to prep the GitHub project, Codex and Qwen to do research for ideas on how to overclock the chips, feasibility of hacks I wanted investigating
10) Asked Codex and Qwen to identify bugs Vs specs, it found a few in event sequencing, resuming events, wrong bits in packets etc.
11) Switched Codex to Max after the the bugs were fixed because the driver performance was laggy, and recommendations from Qwen and Codex Medium/High for optimisations either caused degradations in some way (e.g. DMA was slower) and asked it to audit and optimise the code. I did this over 3 nights due to credit limits getting hit, again 1 to 3 changes at a time.
12) After I was happy with the quality ran the licencing checks again past Qwen and Codex and set up the project on GitHub, held private until I got workflows working.
For dual-monitor versions?
One avenue I looked at for a real 2560px width was that the second controller was physically independent and could have different hardware limits of the first controller by virtue of supporting DVI directly (but not being physically connected to another port).
Unfortunately other controller is logical so that was a bust.
VGA displays are something of a dying breed, and HDMI is the single likeliest interface you might find on a random newish display, so there is a market for absolute cheapest, most basic HDMI output device you can make. If you're going to build that interface, 1080p is the resolution you need to target. My point was simply that 16MB is just barely enough to build that interface, and barely enough is still enough.
^ / 1024^2[bytes/MB] = 23.73[MB]
I have like 4 drivers to upstream myself, plus a couple of patches here and there. Quality is good and they're tested, and while I understand the code and how things work low level, I wouldn't be able to write them myself.
The dev on this driver used a combination of local Qwen 3.6 and 3.8 27B for admin and basic work, and extensive Codex 5.6 Sol Max to catch the issues I found and do last stage optimisations / isolate the bugs.
I'll freely admit I relied heavily on AI, my expertise and day job is in other software stacks.
I stand on the back of giants :)