SimCity SA-1 - First Beta Release - We are Back!

Hi everyone! It has been a long time since my last post here. First of all, I want to sincerely apologize for my long absence and thank you so much for sticking around to read this.

A lot has changed over the past few years in my life, my engineering career, and across the retrogaming scene. However, I never lost my passion for SNES optimization project, especially the SA-1 chip. I preferred to wait until I had something solid and exciting to share before making a new post, and today is finally that day.

I am happy to announce that the first beta version of SimCity SA-1 is now available for download.

You can download under the 'Attachments'. Note that this is a BPS patch. You will need a clean, original SimCity (USA) SNES ROM and a BPS patcher like Floating IPS (Flips) to apply it.

Features

The SA-1 is a powerful enhancement chip that introduces a 10.74 MHz co-processor, a custom hardware arithmetic engine, an advanced high-speed ROM and RAM mapper, and more. SimCity SA-1 integrates this hardware into the game and rewrites the internal logic to take full advantage of it.

Here is what is featured in this first beta release:

1. 4x to 6x Faster City Simulation: The heavy core simulation logic has been successfully offloaded from the SNES CPU to the SA-1 CPU. Meanwhile, tasks like handling the UI, processing text messages, and placing RCI zones or buildings remain on the SNES CPU in parallel. This allows the SA-1 to focus 100% of its cycles on simulation performance.

   • Final objective: Achieve 10x faster simulation speed alongside a locked 60 FPS UI.

2. Faster Terrain Generation: The map generation screen in the "Start New City" menu is now... less bad :) -- While the stock SNES version takes roughly 12 seconds to generate a new terrain, the SA-1 CPU processes in about 4 seconds.

   • Final objective: Reduce this to under 2 seconds or implement a smooth, real-time generation animation.

3. Enhanced Power Supply Simulation: Placing new power-dependent structures now updates the grid instantly. Additionally, loading an existing save file will no longer trigger the awful 1-2 month power outage bug.

   • This was solved by rearranging the power supply subroutines before the SA-1 simulation ticks.

What is still planned in the next versions:

1. Fluid 60 FPS UI: With the simulation safely running on the SA-1 side, the SNES CPU stays idle every 3/4 frames. The plan is using the spare time on the SNES CPU to improve overall rendering speed, with the objective of 60 FPS and instant tile updates (including proper map scrolling support).

2. Native Mouse Support: Adding native SNES Mouse support to bring the gameplay experience closer to the PC version. The mouse will map to Controller Port 2, leaving Port 1 free for standard joypad hotkeys.

3. Enhanced Graphs and Heatmaps: Moving the entire background graphics generation to the SA-1 chip and using CC-DMA (Character Conversion DMA) to deliver semi-real-time map updates without freezing the gameplay loop.

4. Expanded Map Pools: After some tests I found out that terrain algorithm can generate much more unique map IDs than planned. I am looking into expanding the valid map numbers from the original 000–999 range up to 0000–9999 or higher.

5. Community Wishlist: Please drop a comment below if you have specific features you want to see! I know mouse support and the power grid fix are highly requested, but I am entirely open to more ideas :)

Known Issues & Beta Quirks

Unthrottled Simulation Speed

The game simulation can be too much fast in the initial years. I recommend turning on the "Auto $" option and playing with the "slow" speed until you stabilize your city. It's planned in the future version a smart speed control that throttles SA-1 on the "slow" and "mid" speed values for small cities (fast to simulate).

Below screenshot demonstrates the speed options available:

This screenshot shows the "Auto [ $ ]" option, which skips the annual tax rate and funding screen:

The above options should make the gameplay experience better. Keep in mind that every year your account balance is updated by taxes collected + funding, so if you turn "Auto [ $ ]" and you're low on money, there is a risk of getting bankrupt and kicked from the game.

Strict 256 KB BW-RAM Requirement

The SA-1 architecture supports a maximum of 256 KB of BW-RAM. My previous patches only required 32 KB or 128 KB, making this the first project where I have pushed the hardware to its absolute limit. Because this is double the standard 128 KB SRAM threshold of typical SNES games, older emulator builds or flashcart firmwares might struggle to boot it.

I confirmed to work with Snes9x 1.63+; Mesen 2.2.1+ and bsnes-plus-v05, but a few years ago it was common to none of them support it.

• If you open the game and it don't boot, it's likely because of that. Please message me with what emulator you tried using and the version of it.

• bsnes-plus and similar bsnes 0.7x versions requires a special XML mapper to accept the 256 KB BW-RAM (available under attachments - ensure to rename the XML file with the same name as the SMC/SFC ROM file).

• Due to a recent move, I haven't been able to unbox and test this on native FPGA hardware (like the FXPak Pro/sd2snes or MiSTer) yet. If you try it on hardware, please let me know your results in the comments!

The future is unknown: I might get able to reduce to 128 KB, with a con of reducing to 1 city save only or keep 256 KB and increase number of saved cities up to 9 cities. Maybe I can offer both options, if I get able to reduce the memory requirements to 128 KB. For now, the game requires 256 KB and you can save up to 2 cities.

100% Parallel game

Unlike previous patches, SimCity SA-1 operates as a fully asynchronous, parallel 14.32 MHz dual-CPU engine (10.74 MHz SA-1 + 3.58 MHz SNES). Because the processors coordinate via handshakes, there is a slight chance that text events (like Dr. Wright's pop-ups) might occasionally display corrupted text if a race condition occurs during cross-CPU memory reads. If you encounter this, please drop a comment with a screenshot and your save state data so I can debug the collision.

Next steps

I appreciate any feedback here. Thank you for reading the post and I hope you enjoy this initial version. As always, beta versions can get affected by bugs, so ensure to make some save states and frequently save your map to not lose progress.

Again, let me know if you want any feature specific to the game. Expect for now an update every 10-15 days of new enhancements and beta releases until the final version is done. Enjoy!