Pcsx2 150 Dev Build 2021 ((free)) May 2026

PCSX2 1.7.0 development builds (often referred to as the 1.5.0/1.7.0 dev cycle) in 2021 marked a "Golden Era" for the emulator, introducing some of the most significant architectural changes in its 20-year history. While there isn't a single "PCSX2 150" version (as the dev builds jumped to 1.7.0), the 2021 updates fundamentally changed how the emulator looks and performs. 1. The "Big Game Changer": The Qt Desktop GUI

For nearly two decades, PCSX2 used an aging "WX" interface that was clunky and required multiple windows. In 2021, the dev team began the transition to a Qt-based interface Modern Look

: It introduced a "Game Grid" view with box art, similar to DuckStation or Dolphin. Ease of Use

: It eliminated the need for "Global" vs "Per-Game" settings hacks; users could finally right-click a game and set its specific properties easily. Automatic Updates

: The dev builds introduced an integrated updater, meaning users no longer had to manually download new builds from the website every few days. 2. Performance Breakthroughs

2021 saw massive optimizations that made high-end PS2 emulation possible on humbler hardware: Vulkan Backend

: The long-awaited Vulkan renderer was heavily refined in 2021. This provided a massive speed boost for users with AMD GPUs or integrated Intel graphics, who previously struggled with the OpenGL backend. Instant Loading

: The "Fast Boot" and ISO loading times were slashed, making the transition from desktop to gameplay nearly instantaneous. 3. Enhanced Visual Features Texture Replacement

: One of the most "interesting" features added in the 2021 dev cycle was support for custom texture packs. This allowed the community to release 4K HD Texture Mods for classics like Final Fantasy X Metal Gear Solid 3 Integer Scaling

: Added to ensure that upscaled 2D sprites remained crisp rather than becoming blurry when playing at 4K resolutions. 4. Massive Compatibility Fixes

Several "unplayable" or "broken" titles saw fixes in these builds: Snowblind Engine Games : Titles like Baldur's Gate: Dark Alliance Champions of Norrath

, which famously had broken shadows and textures for a decade, finally became playable without massive graphical "hacks." Mipmapping Fixes

: Fixed the "black lines" and "blurry distance" issues in hardware mode for games like Ratchet & Clank Jak and Daxter Why 2021 was the "Turning Point"

Before 2021, PCSX2 felt like a "legacy" tool—powerful but difficult to configure. The 1.7.0 dev builds (which superseded the 1.5.0 branch) transformed it into a modern, user-friendly application that rivals the best emulators in the world. specific hardware

works best with these 2021 Vulkan updates, or are you looking for setup guides for the new Qt interface?

PCSX2 1.5.0 development builds represent a significant bridge between the older 1.4.0 stable release and the 1.6.0 version that arrived in May 2020. By 2021, most active development had actually moved on to version 1.7.0

, as the team transitioned to a new versioning scheme after 1.6.0 was finalized Context of 1.5.0 in 2021

While users often search for "1.5.0 builds" due to legacy guides, by 2021, these builds were essentially the foundation of what became the 1.6.0 stable release Stable vs. Dev:

In the PCSX2 ecosystem, even numbers (1.4, 1.6) are stable, while odd numbers (1.5, 1.7) are development/nightly builds. Evolution:

If you are specifically looking for 2021-era updates, you are likely looking for the 1.7.x nightly builds , which introduced massive changes like Vulkan support and a revamped UI. Key Improvements from the 1.5.0 Era

The development cycle that defined 1.5.0 (and leading into 1.6.0) brought several game-changing features: GSdx Graphics Enhancements:

Massive improvements to the OpenGL backend, fixing long-standing issues like shadows in Crash Twinsanity and performance in the Ace Combat Game Compatibility:

By the end of this cycle, almost every PS2 game became playable or better preserved, with specific fixes for titles like Big Mutha Truckers Gran Turismo 4 Performance Optimizations:

High-level changes to how the emulator handles "denormal-removal shuffles" made it up to 10x faster

for certain users, particularly those on newer CPUs like Ivy Bridge or later. 2021 Specific Milestones (1.7.x Transition) If you are strictly following 2021 development: Q4 2021 Progress:

Significant PRs were merged to improve vertex processing and division accuracy, which helped remove visual glitches without sacrificing speed. Legacy Archive: You can find these specific 2021 builds in the Official PCSX2 Build Archive on GitHub

, which houses 7zip-compressed versions of these historical releases for regression testing. Summary Table: Evolution of Versions Status in 2021 Major Highlight Older plugin-based system. Development Superseded The "Nightly" era that became 1.6.0. Stable (2020) Current Stable Cumulative fixes from 1.5.0 dev cycle. Active (2021) Recommended Added Vulkan support and began UI overhaul. Archive of Legacy Builds of PCSX2 - GitHub

The Evolution of : From 1.5.0 Dev Builds to the 2021 Revolution The year 2021 marked a transformative period for

, the leading PlayStation 2 emulator. While the "1.5.0 dev" era technically concluded with the stable release of version 1.6.0 in May 2020, the momentum of those builds laid the groundwork for the massive 1.7.0 development cycle that defined 2021. For enthusiasts looking back at this era, it represents the moment PCSX2 shed its legacy skin to become a modern powerhouse. The Bridge Between Generations pcsx2 150 dev build 2021

In the early days of 2021, many users were still transitionally using late dev 1.5.0 builds because they were perceived as "tried and true." However, the PCSX2 team had already moved the development frontier to version 1.7.0. This new branch didn't just iterate on the 1.5.0 groundwork—it fundamentally rewrote how the emulator interacted with modern hardware. Key Milestones of the 2021 Development Cycle

The development builds released throughout 2021 introduced features that users of the old 1.5.0 versions could only dream of:

Native 64-bit Support: One of the most significant leaps was the official support for 64-bit versions. This allowed the emulator to better utilize modern system memory and provided a substantial performance boost across the entire PS2 library.

The Vulkan Renderer: Toward the end of 2021, the Q4 Progress Report highlighted work on the Vulkan backend. This provided a faster, more efficient alternative to OpenGL and Direct3D, especially for users on AMD and Intel integrated graphics.

Removal of the Plugin System: For nearly two decades, PCSX2 relied on a clunky "plugin" architecture. In 2021, the developers began integrating these components directly into the core emulator, simplifying setup and improving stability.

Transition to Qt Interface: While the old "WxWidgets" UI from the 1.5.0 days was functional, it felt dated. 2021 saw the heavy lifting for the new, modern Qt-based interface, which brought features like game covers and per-game settings. Why Some Users Still Hunt for "1.5.0"

Despite the massive improvements in later builds, some community members on Reddit occasionally noted that certain "potato" (low-end) PCs struggled with the increased system requirements of the modern 1.7.0 builds. This created a niche demand for the final, highly-optimized 1.5.0 dev revisions that offered a lighter footprint for aging hardware. Summary of Version Shifts (2020–2022) Version Status Major Shift Early 2020 1.5.0 (Development) Final refinements before stable release May 2020 1.6.0 (Stable) The culmination of the 1.5.0 cycle 2021 1.7.0 (Development) Introduction of 64-bit, Vulkan, and Qt UI Early 2022 Nightly Builds Renamed from "Dev" to "Nightly" on GitHub

Whether you are seeking the classic stability of the 1.5.0 era or the cutting-edge performance of modern nightly builds, the 2021 development cycle remains the most pivotal year in the emulator's 20-year history.

The year 2021 was a transformative era for PlayStation 2 emulation. While the official "stable" release at the time was the long-standing version 1.6.0, the real magic was happening behind the scenes in the PCSX2 1.5.0 and 1.7.0 development builds.

If you are looking back at the PCSX2 1.5.0 dev builds from 2021, you’re exploring the bridge between the "old school" plugin-based architecture and the modern, high-performance emulator we use today. The Significance of the 1.5.0 Dev Cycle

For years, PCSX2 relied on a complex system of plugins (GSdx, SPU2-X, LilyPad). The 1.5.0 development cycle, which bled into the 1.7.0 "Nightly" builds in 2021, focused on gutting these outdated systems to create a more unified, user-friendly experience.

The 2021 builds were particularly famous for introducing features that finally made difficult-to-emulate games playable for the average user. Key Features Introduced in 2021 Dev Builds 1. The Transition to 64-bit

2021 saw the definitive shift toward 64-bit (x64) builds. Previously, PCSX2 was primarily a 32-bit application, which limited memory access and performance. The x64 dev builds provided a noticeable stability boost and paved the way for more advanced graphical features. 2. Vulkan API Support (The Game Changer)

Perhaps the biggest milestone in late 2021 was the initial implementation of the Vulkan renderer. For users with AMD graphics cards or integrated Intel graphics, Vulkan offered a massive performance leap over the aging OpenGL and DirectX 11 backends. It reduced "stutter" and allowed for much better scaling at higher resolutions. 3. Automatic Game Fixes

Prior to the 2021 dev builds, users often had to manually toggle "Hardware Hacks" to fix ghosting in Ratchet & Clank or blurry textures in Black. The 1.5.0/1.7.0 dev builds introduced a massive database of automatic game fixes, meaning the emulator would detect the game and apply the necessary patches instantly. 4. Achievement Support (RetroAchievements)

2021 was also the year PCSX2 integrated with RetroAchievements. This allowed players to earn modern-style trophies for classic PS2 titles, breathing new life into games like Final Fantasy X and Metal Gear Solid 3. Why People Still Search for "PCSX2 1.5.0 Dev Build 2021"

Even though PCSX2 has moved on to version 2.0+ with a sleek new "Qt" interface (similar to DuckStation), many enthusiasts still reference the 2021 dev builds for a few reasons:

Legacy Plugin Support: Some niche mods or older hardware setups still play better with the old plugin-style interface found in 1.5.0.

Low-End Hardware: Certain 2021 builds were highly optimized for older CPUs before the emulator’s system requirements began to creep up.

Transition Documentation: Many YouTube tutorials and forum guides from 2021 specifically link to these builds, making them a common "time capsule" for new users. How to Get the Best Experience Today

While the 1.5.0 dev builds were revolutionary in 2021, the emulator has since been completely overhauled. If you are looking for those 2021-era improvements, they have all been refined and included in the latest Nightly builds (v1.7.x and v2.0+). Why you should update beyond 1.5.0: Big Picture Mode: A full controller-friendly UI. Texture Replacement: Easily install HD texture packs.

No More Plugins: Everything is built-in; no more messing with GSdx settings. Final Verdict

The PCSX2 1.5.0 dev builds of 2021 represented the "growing pains" of the world’s best PS2 emulator. It was the year the project stopped feeling like a piece of legacy software from 2004 and started feeling like a modern, high-end gaming platform. Whether you're chasing nostalgia or technical curiosity, these builds remain a testament to the dedication of the emulation community.

In 2021, the world of PlayStation 2 emulation was at a crossroads. The community had long relied on the 1.6.0 stable release (launched in May 2020), but the real magic was happening in the background within the 1.7.0 development builds. While "v1.5.0" refers to the older dev cycle that led to the 1.6 stable release, 2021 was the year users began flocking to the "nightly" 1.7.0 builds for features that would eventually redefine the emulator. The Quest for the Perfect Build

The story of a typical user in 2021 was one of constant experimentation. You didn't just "download PCSX2"; you joined a hunt for the latest Github nightly build. This was the year that:

Vulkan Support began to surface in dev builds, promising massive performance gains for AMD users who had historically struggled with OpenGL.

64-bit builds became the new standard, moving away from the aging 32-bit architecture to offer better modern system compatibility.

The "No More Plugins" Era started to take shape, as developers worked to integrate legendary plugins like GSdx and LilyPad directly into the core emulator for a more "just works" experience. A Tale of Two Versions For a gamer in 2021, the choice was a rite of passage: PCSX2 1

PCSX2 1.5.0 Dev Build 2021: A Comprehensive Review of the Latest Features and Improvements

The world of PlayStation 2 emulation has seen significant advancements over the years, with PCSX2 being one of the most popular and enduring emulators available. The PCSX2 1.5.0 dev build 2021 is the latest iteration of this beloved emulator, boasting a plethora of new features, improvements, and bug fixes. In this article, we'll take a closer look at what's new and exciting in this build, and explore how it enhances the overall gaming experience for PS2 enthusiasts.

Introduction to PCSX2

For those unfamiliar with PCSX2, it's an open-source PlayStation 2 emulator that allows users to play PS2 games on their PC. The emulator has been in development since 2002 and has come a long way since its inception. With a strong focus on accuracy, compatibility, and performance, PCSX2 has become the go-to emulator for PS2 gamers worldwide.

PCSX2 1.5.0 Dev Build 2021: Key Features and Improvements

The 1.5.0 dev build 2021 of PCSX2 is a significant milestone in the emulator's development, with numerous improvements and new features that enhance the gaming experience. Some of the key highlights include:

Improved Performance: The emulator now boasts improved performance, thanks to optimizations in the recompiler and the integration of AVX-512 instructions. This results in smoother gameplay and reduced lag.
Enhanced Compatibility: The emulator's compatibility with PS2 games has been significantly improved, with many more titles now playable without major issues. The 1.5.0 dev build 2021 also includes improved support for games that use the PS2's hardware-based transform, clipping, and lighting (TCL) features.
New GUI: The emulator's graphical user interface (GUI) has been revamped, providing a more modern and intuitive look. The new GUI also includes improved categorization and searching of games, making it easier to find and configure your favorite titles.
Better Support for Modern Controllers: PCSX2 1.5.0 dev build 2021 now offers improved support for modern controllers, including the DualShock 4, Xbox One, and Nintendo Switch Pro controllers. This means that gamers can enjoy a more authentic experience with their preferred controllers.
Vulkan and Metal Renderers: The emulator now includes experimental support for Vulkan and Metal renderers, which provide improved performance and compatibility compared to the traditional OpenGL renderer.

Technical Details and Changes

The PCSX2 1.5.0 dev build 2021 includes a range of technical changes and improvements under the hood. Some of the notable changes include:

Updated Recompiler: The emulator's recompiler has been updated to improve performance and reduce overhead. This results in faster emulation speeds and reduced CPU usage.
AVX-512 Support: The emulator now supports AVX-512 instructions, which provide a significant boost to emulation performance on compatible CPUs.
Improved Memory Management: The emulator's memory management has been improved, reducing the risk of crashes and improving overall stability.
OpenGL 4.3 and Higher Support: PCSX2 1.5.0 dev build 2021 now supports OpenGL 4.3 and higher, providing improved performance and compatibility with modern graphics cards.

Configuration and Setup

Configuring PCSX2 1.5.0 dev build 2021 is relatively straightforward, and the emulator includes a comprehensive guide to help users get started. Here's a brief overview of the setup process:

Download and Install: Download the PCSX2 1.5.0 dev build 2021 from the official website and follow the installation instructions.
Configure the Emulator: Launch the emulator and configure the basic settings, such as the language, resolution, and audio output.
Set Up the Controls: Configure your controller or keyboard settings to suit your gaming preferences.
Load a Game: Load a PS2 game disc or ISO file and adjust the emulator settings as needed to optimize performance.

Conclusion

The PCSX2 1.5.0 dev build 2021 is an exciting and significant update to the emulator, offering improved performance, compatibility, and features. With its enhanced GUI, better support for modern controllers, and Vulkan and Metal renderers, this build provides a compelling experience for PS2 enthusiasts. Whether you're a seasoned gamer or just starting to explore the world of PS2 emulation, PCSX2 1.5.0 dev build 2021 is definitely worth checking out.

Frequently Asked Questions

Q: What are the system requirements for PCSX2 1.5.0 dev build 2021? A: The emulator requires a 64-bit CPU, 4 GB of RAM, and a graphics card that supports OpenGL 4.3 or higher.
Q: Can I play all PS2 games with PCSX2 1.5.0 dev build 2021? A: While the emulator has improved compatibility, some games may still experience issues or not work at all. You can check the PCSX2 website for a list of compatible games.
Q: How do I configure my controller to work with PCSX2 1.5.0 dev build 2021? A: The emulator includes a comprehensive guide to configuring controllers. You can also refer to online resources and forums for specific guidance on setting up your controller.

Downloads and Resources

PCSX2 1.5.0 dev build 2021: Download the latest build from the official PCSX2 website.
PCSX2 Documentation: Refer to the emulator's official documentation for configuration guides and troubleshooting tips.
PCSX2 Forums: Join the PCSX2 community forums to discuss the emulator, share tips, and get help with any issues you may encounter.

To set up the PCSX2 1.5.0 development build from 2021, it is important to note that this specific version is part of a legacy transition period. PCSX2 uses odd numbers (1.5.0, 1.7.0) for development builds and even numbers (1.4.0, 1.6.0) for stable releases. By 2021, most 1.5.0 builds were superseded by the 1.6.0 stable release and later 1.7.0 Nightly builds. 1. Downloading and Installation

Locate the Build: You can find archived versions of these specific builds on the official PCSX2 Legacy Build Archive on GitHub.

Dependencies: Ensure you have the Visual C++ 2015-2019 Redistributable (x64) installed, as these builds require it to run.

Portable Mode: It is highly recommended to use the Portable version. Extract the .7z file into a dedicated folder (e.g., C:\Games\PCSX2) using a tool like 7-Zip. Avoid placing it in Program Files to prevent permission issues. 2. Initial Setup (The First-Time Wizard)

Language & Theme: Select your preferred interface language and theme (e.g., Dark Fusion).

BIOS File: You must provide your own PS2 BIOS. Place your BIOS files in the /bios folder within your PCSX2 directory, then click Refresh List and select the correct region.

Plugins: For 1.5.0 builds, keep the default plugins unless you have specific hardware needs. The GSdx plugin is the most critical for graphics. 3. Core Configuration for 2021 Dev Builds [Guide] : Configuring PCSX2 1.5.0 with brief explanation.

In the world of PlayStation 2 emulation, the PCSX2 1.5.0 development build represents a crucial bridge between the long-standing stable releases and the modern "Nightly" era of the project. While many users in 2021 initially sought 1.5.0, it's important to understand how the versioning worked and why the project moved beyond it. The Role of Dev Build 1.5.0

In the PCSX2 versioning scheme, odd numbers (like 1.1, 1.3, 1.5) indicate active development cycles, while even numbers (1.4.0, 1.6.0) represent tested, stable releases.

Transition Period: The 1.5.0 development branch was the testing ground for what eventually became the PCSX2 1.6.0 stable release in May 2020.

Feature Testing: It introduced major improvements like MipMapping support, which fixed broken textures in games like Ratchet & Clank, and significant updates to the OpenGL renderer for better accuracy.

2021 Status: By 2021, the dev branch had already moved to version 1.7.0. Users searching for "1.5.0" in 2021 were often looking for specific legacy compatibility or weren't aware that 1.7.0 had superseded it with even more features. Key Features and Improvements

For those still utilizing 1.5.0 builds, several technical milestones stand out compared to the older 1.4.0 stable: 1.7.0 dev builds closing after booting ISO or BIOS

PCSX2 1.5.0-dev builds from represented a significant era of transition for the emulator, bridging the gap between the older 1.4.0/1.6.0 architecture and the modern 1.7.0+ "Nightly" versions. Key Features and Updates in 2021 Builds Improved Performance : The emulator now boasts improved

By late 2021, the 1.5.0-dev branch (which eventually became the foundation for 1.7.0) introduced several transformative features: Vulkan Renderer Support

: One of the most significant additions was the early implementation of the

API. This provided a massive performance boost for AMD and Intel GPU users who previously struggled with OpenGL performance on Windows. 64-bit (x64) Support

: This year marked the definitive shift toward 64-bit binaries, improving memory management and paving the way for more advanced features like high-resolution texture replacement. Automatic Game Fixes

: The dev builds began integrating "GameDB" updates that automatically applied the best settings and patches for specific games, reducing the need for manual "Speedhack" tweaking. Improved ISO Compression : Support for

compressed ISO reading was fixed and refined in December 2021, allowing users to save significant disk space without losing performance. Initial Texture Replacement

: Users could begin experimenting with custom high-definition texture packs, a feature that significantly modernized the look of classic titles. Controller Backend Overhaul : The introduction of

for controller input improved compatibility with modern gamepads like DualSense and Xbox Series controllers. Usage Context

In 2021, these "dev" or "nightly" builds were often preferred over the "Stable" 1.6.0 release because they contained years of optimizations and compatibility fixes that the stable version lacked. Feature Category Vulkan support, Integer Scaling, and improved Internal Resolution upscaling.

Refinements to the SPU2-X plugin to reduce crackling in demanding games like

Transition away from the old "Plugin" selector toward a more unified, modern interface. Important Note

: If you are still using a 1.5.0 build from 2021, it is highly recommended to update to the latest PCSX2 Nightly (v2.0+) available on the official PCSX2 download page

. Modern versions include a fully overhauled "Qt" interface, significantly better performance, and integrated per-game settings. transferring your save files from an old 1.5.0 build to the newest version?

[Bug]: .gz compressed ISO reading broken · Issue #5162 - GitHub

Short informative story — "PCSX2 1.5.0 dev build (2021)"

In the dim glow of a cluttered desk, Jonas booted an old PlayStation 2 disc — a title that had defined his teenage summers. The console gathering dust in the closet no longer answered when plugged in, but on his laptop a different kind of resurrection was possible. He launched PCSX2, the PS2 emulator he'd used once, years before, and noticed a new development build labeled 1.5.0 (2021).

The dev build was a promise: months of contributor patches, experimental features and compatibility fixes stitched together by a small, passionate team. Jonas clicked through the changelog like a reader flipping pages of a mystery. There were notes about improved recompilers, better VU threading, fixes for notoriously problematic titles, and a laundry list of platform-specific tweaks — Windows scheduler improvements here, OpenGL rendering adjustments there. For people like him, frustrated by stuttering cutscenes or graphical glitches that made certain games unplayable, the build felt like a lifeline.

He installed it carefully, mindful that development builds could be unstable. The interface looked familiar but faster. His favorite game — a sprawling RPG with lush 3D environments — loaded. Where the stable release had dropped frames and glitched textures, the dev build smoothed character animations and fixed a rendering bug that had previously erased distant foliage. A previously broken mini-game now ran perfectly; a subtle audio desync that had always annoyed him was reduced to a whisper.

Jonas knew not every change was universally beneficial. A forum thread he skimmed warned that some experimental speed hacks could cause crashes in other titles, and that savestate compatibility was not guaranteed between versions. But that was part of the trade-off: bleeding-edge fixes in exchange for occasional instability. What attracted him most was the openness — commit logs, issue trackers, and discussion threads where users and developers exchanged stack traces, test logs, and screenshots. Community members filed bug reports with precise reproduction steps; developers returned builds addressing those steps within days. The dev build was as much a living conversation as a program.

Over weeks he toggled settings, reported a reproducible freeze on a lesser-known minigame, and attached traces. A developer thanked him and asked for a save file; two weeks later, a new dev snapshot landed with the freeze fixed. Jonas felt a small, satisfying connection to the project: his report, their patch, a game restored.

The 1.5.0 dev series also showed how complex emulation was — a mix of reverse engineering, clever approximations, and careful optimization. Emulating the PS2’s unusual multi-processor design required both precision and pragmatic compromises. Some games demanded exact timing to work, while others were forgiving; the devs balanced accuracy against performance to make titles playable on modest hardware.

By autumn, Jonas had a library of fixed quirks and documented workarounds. The dev builds didn’t promise perfection, but they offered progress you could try yourself. For him, the 1.5.0 dev builds were a reminder that software can be collaborative resurrection: old code running again thanks to new eyes, and a community turning technical challenges into small victories for anyone who wanted to play the past on modern machines.

Overview

The 2021 development builds of PCSX2 (version 1.5.0) mark a noticeable shift in the emulator’s evolution. While the stable 1.6.0 release was already solid, these dev builds introduce better performance, fewer graphical glitches, and improved game compatibility—especially for titles that were previously "unplayable."

What Still Needs Work

Stability: Being a dev build, crashes still happen—especially when toggling settings mid-game or using heavy upscaling (4K+).
Audio: Occasional crackling or desync in demanding scenes, even with async mix enabled.
BIOS required: As always, you must provide your own BIOS dump. No legal workaround.
Controller config: Still slightly clunky for non-Xbox controllers; third-party tools like DS4Windows help.

Step 4: Widescreen Hacks

The 2021 dev builds included over 800 game-specific widesrum patches. Go to Patches > Enable Widescreen Patches. This forces 16:9 rendering without stretching HUDs, though you may need to manually download the .pnach files for obscure titles.

5. Shadow of the Colossus

Result: 30 FPS (Native console cap) Reason: This remains the benchmark. The 2021 dev builds require Blending Accuracy: High and CRC Hack Level: Aggressive to remove the green tint from the sky. Expect 80% speed on a laptop.

5. Stability vs. Features: Should you use these builds?

If you are looking to download a build from this era, here is the assessment:

Warning: Save states (memos) created on development builds generally cannot be loaded on stable builds, and vice versa. 2021 builds introduced a new compression method for save states, breaking backward compatibility in some instances.