Blog

In the investigation for issues like [#679](https://github.com/devmiyax/yabause/issues/679) and [#664](https://github.com/devmiyax/yabause/issues/664), I found strange behaviors in SEGA Saturn emulation of Yaba Sanshiro. DMAC(Direct Memory Access Controller) starts memory copy despite CD-ROM data is not read yet. The master CPU start copy to VRAM before the slave CPU finishes copying data to the source region. I write code that reproduces these behaviors and runs it on the real SEGA Saturn. it shows that memory access timing is the cause of this matter.

I've been implementing the new dynamic recompile CPU emulator for ARM64v8a. It means Yaba Snashiro will run on 64bit CPU natively. The result is 64bit code is faster than 32bit code slightly, not so much. But I'm happy. Slow progress is still progress.

Recently I'm trying to develop the new graphics emulation core using Vulkan. Vulkan is the latest graphics API which can access GPU more directly than OpenGL . Today I successes to render NBG0! it's need much more time to make it playable. since speed is the biggest problem of SEGA Saturn emulation, my effort will be worth wile.

I rewrite almost of the shader code. The concept of this change is 'Move'em to GPU'. it means that moving code running on CPU to GPU. In general speaking, GPU is fast because of their parallel processing. CPU has just 2-4 cores, on one hand, GPU has hundreds or thousands cores. Yeah, That's great indeed. There is one more thing GPU is superior than CPU. That is GPU can compile and load program dynamically. You can run the minimum code when you need. That's very important for a complicated system like SEGA Saturn emulation. For example, VDP2(Sega Saturn Display unit) has 3 blend modes, 4 blend condition options, and 3 color mode. That means you need 3x4x3=36 branches to draw just one pixel. On CPU you need to prepare all branches you need statically. it really complicated and makes emulation slow down. On GPU, because you can dynamically compile shader code, you can organize the parts of the code and run the generated code straightly( without branches ). For This 'Move'em to GPU' concept,

Yaba Sanshiro has the cloud save data function. If your local storage does not have save data, you can copy back them from cloud storage. You can also save your cheat code to the cloud storage. In addition, you can share your cheat code. Please rate the cheat so that good cheats can be found easily.

Since backup data occasionally get broken, you need to back up your backup data. You need to copy entire backup data to share it to another devices.To Input Cheat code is very irritable. Everybody want to easily use proven cheat codes.

'uoYabause' got banned, I need to change the name. I've always been asked how 'uoYabause' should be pronounced. I also don't know. So I think it's a good chance. 'Yaba Sanshiro' is the new name for our SEGA Saturn emulator.

They say that

I've hacked the Backup library in SEGA Saturn. and succeeded to increase internal backup memory from 32KB to 8MB. And I've added the memory manager screen. Now you can edit backup memory without BIOS.

The most irritable thing when I use an emulator on Android devices is **transferring game files to the device**. Generating ISO image, Connecting USB cable, Installing adb or MTP driver, Transfering using adb command or explorer. sometimes explorer freezes while transferring. Broken ISO images. blah blah blah... Everything is irritable and disgusting.

New cpu core is now ready! it's twice faster than interpreter cpu.

Yabause has two CPU emulation options. Interpreter CPU is easy to understand but slow. Dynamic recompile CPU ( also called Dynarec) which was written by Ari64( I think he is the genius) is very fast but is very complicated and has many bugs :( So I decided to implement the new CPU emulation.

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I don't know why, but I received many requests about cheats support. so I've Implemented it.

* Improve onscreen touch pad.

### Improving Framebuffer Emulation

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I fixed many bugs in SCUDSP emulation. Then finally Shining Force 3 magic effects are enabled!