Your PC's BIOS is a black box that even open-source firmware can't completely replace

Published Nov 5, 2026, 11:30 AM EST Ismar is a Senior Author at How-To Geek. He previously worked as a writer, editor, and general manager at a content agency before joining the team in 2023. He began his writing career in 2021 after completing a BA in English Language and Literature. Beyond How-To Geek, Ismar has contributed to Red Stag Fulfillment and Authority Hacker. He has also worked on various SEO projects to help clients improve their search visibility. Ismar has been around Windows PCs since the age of three, so friends and family naturally chose him as the resident tech support. His projects often involve tinkering, such as disassembling mechanical keyboards and gaming mice to mod his beloved gear. He also enjoys pushing hardware to the max through overclocking while staying on a reasonable budget. An avid gamer, Ismar has logged thousands of hours across various genres, including first-person shooters, RPGs, racing games, and roguelites. When he is not at his desk, he is probably exploring other people’s phones to discover their quirks and features or experimenting with the latest AI tools. In his free time, Ismar enjoys spending time with his wife, working out at the gym, playing guitar and bass, cooking gourmet meals, and traveling. Above all else, he’s a proud cat owner. The first thing your PC does when you press the power button is initialize its hardware, a task handled by its BIOS before handing control over to the bootloader that starts your OS. But even if you use an entirely open-source OS, the underlying firmware that gets your computer running is usually largely proprietary, meaning a critical part of your PC remains a complete mystery. Projects like Coreboot offer an open-source alternative to conventional BIOSes, but because of how modern PCs work, replacing your firmware doesn't necessarily make your PC entirely open-source. Your motherboard's firmware relies on a lot of proprietary code You have to trust what you can't see Early PC BIOS firmware was relatively small — its entire code could fit into just a few kilobytes. Over time, this grew into the massive modern UEFI (Unified Extensible Firmware Interface) implementations we know today, which take up several megabytes of space. Some even ship on chips as large as 64MB. This is because UEFI contains a lot of different parts, including complex graphical interfaces, advanced performance and security features, and an extensive hardware compatibility support list. Although features and layouts vary between brands, modern motherboard manufacturers like ASUS, Gigabyte, MSI, and ASRock all ship proprietary UEFI firmware. The core code of many consumer BIOSes comes from a single company you've likely heard of: American Megatrends (AMI for short). The code behind these modern UEFI implementations comes from several sources, including independent firmware vendors, Intel or AMD, motherboard manufacturers, and various third parties. It's a Frankenstein-like mishmash of closed-source code assembled from different generations and sources, with an ever-growing collection of features, hardware support, and security mechanisms added over time. Once you factor in legacy compatibility code, it's easy to understand the complexity and size of modern firmware. This situation is a complete nightmare for open-source enthusiasts, right-to-repair advocates, and cybersecurity professionals. UEFI firmware has extensive privileges over your PC's hardware, so vulnerabilities that allow attackers to compromise it can quickly become a massive security concern. Because motherboard manufacturers rely on code that isn't written by them, a vulnerability in a shared component could potentially affect millions of machines at the same time. Unlike publicly available open-source code, which can theoretically be independently audited and improved by anyone, proprietary implementations remain out of public reach. We're effectively forced to trust manufacturers and their suppliers to get everything right, which is why some people have started looking into open-source alternatives to conventional BIOS firmware. Coreboot is an open-source alternative that gives you more control over your PC A completely different approach to motherboard firmware Credit: Sadenäyttely / Wikimedia Commons / CC BY-SA 4.0 There are several open-source alternatives to proprietary BIOS/UEFI firmware, but Coreboot (formerly known as LinuxBIOS) is arguably one of the most relevant alternatives to conventional proprietary motherboard firmware. Unlike open-source projects that implement the UEFI specification, such as TianoCore EDK II, Coreboot solely focuses on low-level hardware initialization that occurs when you first press the power button, much like traditional BIOS firmware. Because it contains significantly less code, it gives much less material for hackers to work with, while auditors have an easier time finding vulnerabilities. Another benefit of its tiny codebase is that it's much safer and easier to update, while its minimalist approach can significantly reduce boot times. Coreboot's developers claim boot-time reductions of over 70% compared to conventional OEM firmware. After Coreboot initializes the hardware, it hands the boot process over to a payload, which in turn provides what's needed to load the operating system. There are numerous open-source payloads to choose from, including the aforementioned EDK II, SeaBIOS, GRUB, and LinuxBoot, which uses a Linux kernel to handle the remaining boot process. If you like the concept of Coreboot but don't want to configure and build a firmware image yourself, projects like Libreboot and Dasharo offer preconfigured Coreboot-based firmware for supported hardware, making it easier to install and maintain. You can't flash an open-source firmware on just any motherboard Every motherboard is a different challenge One of the biggest limitations of open-source alternatives to proprietary UEFI firmware is their limited hardware support. Coreboot needs board-specific code to initialize the various components of a motherboard. Every motherboard is different, so someone has to develop and maintain the code for each supported board. If you're adamant about using an open-source alternative, you should look into the available open-source firmwares and only buy supported hardware. To give you an example, 3mdeb, the team behind Dasharo, recently ported the firmware to the first AM5 motherboard, the MSI PRO B850-P WIFI. The only (major) caveat is that the openSIL library currently only supports a handful of Phoenix-based Ryzen 8000 series CPUs, further limiting your choice of hardware. Integrated systems like laptops and mini PCs have an advantage when it comes to compatibility, as their hardware configuration is more uniform than that of a custom PC. This makes them some of the best candidates for open-source firmware. In fact, virtually all modern Chromebooks use Coreboot as their primary firmware, which helps explain how these lightweight laptops can achieve such impressive boot times. Even open-source firmware can't eliminate every proprietary component in your PC There are parts you still have to trust Even if you can technically flash open-source firmware onto your PC to gain more control over your system, there are still some bits of proprietary code (called "binary blobs") that you can't easily get rid of. The computer needs these pre-compiled components from vendors like Intel (Intel FSP) or AMD (AGESA and PSP) to initialize some hardware components. Even in the example of the Dasharo port on the AM5 MSI motherboard I mentioned earlier, 3mdeb claims a 79.1% reduction in closed-source firmware code compared to the original firmware. 3mdeb used openSIL instead of AGESA, but it still had to rely on the proprietary AMD PSP firmware. Open-source firmware is promising, but it just isn't yet ready for everyone As things currently stand, the primary goal of open-source firmware like Coreboot isn't to completely eliminate proprietary code, but to reduce our reliance on it, giving us greater control, transparency, and potentially better security in the process. Instead of one huge black box that is the BIOS, you get a mostly open firmware stack with a few smaller black boxes sprinkled here and there. It's definitely not for everyone, though, as you often have to sacrifice some genuinely useful features and hardware compatibility in the process.