Lu

MiSTer Updates – PC8801 Core, PSX RAM requirements and more

Posted on by Lu

PC8801 Computer Core

A computer core for the Japanese PC8801 computer by NEC has recently been released. This was one of Japan’s most popular computers that had a lot of game developer support from companies such as Sega, Enix, Square, Konami and many more.

Using Original Game Boxes to Load Games on MiSTer FPGA

The RMC youtube channel recently posted a video about how he set up a MiSTer FPGA to load games by using the original game boxes.
This was accomplished by setting up a barcode scanning system that will scan the barcode on the game’s box to then load the game on a MiSTer FPGA.
On the video, he goes over the entire setup and shows you exactly how to setup your own system.

Playstation Core Sound and RAM Requirements

Sound is now finally working on the Playstation core. It’s not working for all games but it’s a good start for the core.
30% of the Playstation’s SPU, or Sound Processing Unit, has been implemented.
So as the SPU implementation keeps getting improved, expect more games to start working.

So regarding the PSX core, I want to address two questions that’s been asked a lot. That question is if a second RAM stick will be required for sound.

So Robert, the developer of the core, replied to a reddit post detailing what his plans are for sound. In that post, he mentions that sound will work without a second RAM stick. There will be issues causing sound delays, but not enough of a delay that can be noticeable by a human being. When sound is implemented, he wants to either auto detect the second stick or have the user specify it.

The other question I get and I want to address is, why not increase the amount of RAM on a single stick instead of using two?

The reason for needing two sticks for accurate sound emulation, does not have to do with the amount of RAM. It has to do with the amount of bandwidth. There is a limit on how fast you can send data over the GPIO pins that the RAM chip uses. So no matter how much you increase the RAM, you are still bound by that speed limit. In order to get around that speed limit, you can use more GPIO pins to send more data at the same time, instead of sending data faster.

Unfortunately, if you have an analog IO Board, you are already using the extra GPIO pins, making you decide between accurate sound or analog output.
While you can have analog output over the HDMI port using direct video.
A feature I use a lot is outputting HDMI and analog output at the same time, which won’t be possible when using a second RAM stick.

This is a simplification, but I hope this helps you better understand the reason for using 2 RAM sticks for the playstation core. One of the goals for MiSTer cores is to be as accurate as possible and using 2 RAM sticks  better achieves that goal. 

Jotego Updates

2 New Cores Released to the Public

MiSTer core developer Jotego has released 2 of his cores to the public. These cores are Konami’s Super Basketball and Yie Ar Kungfu. These games are based on similar hardware and Jotego expects we will soon see more games using that hardware. You can download these cores from Jotegos JTBIN github or by using the update all script.

Neo Geo Pocket

Another piece of hardware Jotego is working on is the Neo Geo Pocket. A core is a long way off because right now he’s only working on the CPU and has it at 58% complete.

Toaplan Twin Cobra

For Toaplan’s Twin Cobra, while there’s no code for a core, his team has the game’s sprite circuitry transcribed from the board’s schematics. 

Possible Future Sly Spy Core

Jotego has also ordered the manual for the Sly Spy arcade game. Other games made by the same company had their schematics in the manual, and if that’s the case with Sly Spy, Jotego predicts we will see it in FPGA form really quickly.

CPS1

Finally, with Jotego’s CPS1 core, he fixed a bug that made King of Dragons run at 10MHz instead of 12MHz.

Other Smaller MiSTer Updates

And finally, other smaller updates involve fixes to the video filters on the main MiSTer software and fixes to the Amiga core. Just run the update script to implement these.

About those video filters, I would like to highlight a YouTube channel that does a great job of going over these filters and also the MiSTer Shadow Masks. The channel is called Trash Uncle and he really goes into detail on the new way MiSTer handles video filters. If you’re interested in getting a better CRT look on a modern display then check out his videos.