JOTEGO

Popeye Core Update

(español abajo)

I spent several hours this weekend on advancing the Popeye core. It went from no sprites at all, to pretty much working. I discovered that the ROM set we all use in MAME has the address bits inverted for the object ROMs. At least, when compared with schematics.

Sprite hardware in Popeye is really strange. Indeed, if you see the video you will notice how sprites just disappears around the right edge of the screen. I still don't understand why this happens.

I am again using MiST as the development system....

Boards from Andrew Received

Fresh news. Remember how Andrew had offered a loan of his Double Dragon PCB? The board finally arrived today in outstanding shape. Very nicely packaged and luckily, no custom tax this time.

Andrew also sent a Moonwalker original board (System 18). I have now enough material to tackle a System 16 core as Pierre G. had loaned to me a System 16 board and I bought a Moonwalker bootleg. I may get a System 16 bootleg from a donor too.

As I am getting out of storage room at home I may have to make a System 16/18 core just t...

Commando Core (BETA) Release

I am happy to announce you that all +$3 patrons will receive a download link to the Commando core for both MiST and MiSTer in the next few minutes.

I am also proud to introduce Bruno the ROM Master to you. The ROM Master has produced the accompanying batch file that generates the ROMs, which works with both merged and unmerged MAME files. Thanks!

Note that there are some graphical glitches that seem to be related to the bus arbit...

Arcade PCBs from Japan

The outcome from the poll about which board to buy was to get Double Dragon. However, Andrew Moore,  one of my earliest patrons, offered to loan me his Double Dragon PCB. We are still looking at the best way to send it at the minimum cost from USA to Spain but we can count on his board for this. Thanks Andrew!

I am running out of CAPCOM pre-CPS games with schematics available so I needed to get some PCB...

New Core: Commando

(español abajo)

As I am travelling and I cannot use the FPGA right now I went back to looking at schematics. I started reading the Commando schematics and found that the video hardware is almost identical to that of Ghosts'n Goblins. Game CPU and sound CPU peripherals are also similar to the other CAPCOM games of the same generation I had already done. I will make one (or more) posts explaining how CAPCOM engineers (or maybe just one engineer) was trying different approaches on these games. The protection system is e...

To buy or not to buy

I am travelling this week and next week in Japan. I have located a Street Fighter 1 board in a shop. This is a rare game and there are no schematics available. I also found Renegade and  Double Dragon. And finally I found and I bought Gun Smoke. Gun Smoke is part of the pre-CPS1 games I am wor...

Popeye Sprite Hardware

(español abajo)

Popeye has an unusual sprite generator. The CPU writes the sprite information (which tile, which colour palette and where in screen) in RAM. Once per frame a DMA circuit triggers and copies that region of RAM into a separate buffer. However, there is not enough time to read the buffer completely once written so the number of sprites is limited not by memory but by time.

During the rest of the frame, the contents of the buffer are scanned and compared with a screen line counter that runs slightly...

1942 Logo: Emulation vs Arcade/FPGA

Not many people noticed, certainly Sorgelig did, but the CAPCOM logo at the boot up screen of 1942 is different in MiSTer and MAME. MAME version shows two different boxes moving, whereas MiST(er) version shows just one long box whose length varies. I made that core using only schematics. I didn't have a real PCB and I couldn't find any video of that logo animation on YouTube. But the logo behaviour made sense to me from the schematics point of view as the sprite RAM space was divided in sections for all screen, only left and only right. Some...

Popeye Update

I am sorry I am running late with the beta release but I'm happy to announce that I made a critical step forward this week:

Popeye has a lot of encryption and obfuscation on the board. It is impossible to get it right just with the schematics. However, Scralings had found a report on the obfuscated logic here and MAME had the encryption implemented so I was confident to get it through. But after a lot of work there was no way to get the background displ...

Improved Simulation Flow

I actually had scheduled yesterday as the release date for the beta Popeye core but I got stuck with a problem in the DMA circuit. I thought it would be nice to be able to simulate the schematics directly without having to convert them to text myself. I usually just read them without simulating anything but this time I was a bit confused.

I started copying some schematics to KiCAD 2019-06-17 21:30:05 +0000 UTC View Post

Research Work

I was asked to publish a bit about how I develop the cores. Today I will talk about a small topic: the horizontal pixel count of Popeye.

All video systems need to count pixels. There is always a horizontal count, H, and a vertical count, V. Popeye PCB schematics are available online and except for some chips marked with a different code on purpose, most of it is accurate.

However the H counter has...

Popeye Graphics Explained (2)

Following on this post, let me explain further how the graphics hardware rendering the background worked.  

The general idea is that a memory is written by the CPU with some pixel information and some hardware counters are used to scan the memory while the output of the memory is taken to the screen. The CPU can control how the scan is done by changing the starting locations of the scan. This is used to produce scroll effects.

No...

Items bought thanks to you!

(Español abajo)

Since I started with Patreon I have received a lot of support from you, my patrons. This has been a great incentive to work harder and also with greater enjoyment. But with the extra money I have been able to improve my development setup. These are some of the things I have bought recently: a new solder with accesories, cables to hook up a Commodore 64 and an X68000, a HxC SD floppy emulator for X68000, a small 8" screen to develop on it, a better 2019-06-04 20:27:42 +0000 UTC View Post

Popeye Core

For the last week I couldn’t an image at all first, and then I could only get a display full of zeros. I have finally got real images from the core.

There seem to be a number of issues. But once you get an image it is easier to diagnose what is going on. There is still some problem with the reading from SDRAM and maybe something wrong with the background hardware.

I will release the beta in 1~2 weeks time so this is the paid post for this core. This lets me get the list of patrons for the credits and to send the beta version of...

Popeye Graphics Explained (1)

(español abajo)

Popeye is a great example of single-screen games. Nowadays we are used to exploring giant worlds but Popeye reminds us that a good game design needs no more than one screen. But how was that screen rendered?

The engineers behind this awesome hit combined three different graphics systems. Let's see them!

First, there is a character layer. Using a small ROM memory where each bit represented either transparency or opaqueness, the artists drew all characters seen in the game and also some figur...

Popeye Release Schedule

 I have resumed my work on the Popeye arcade core.  This is the schedule I have for it:

* 30th May: paid post to identify supporters of this core, including patrons of the pause screen

* First week of june: beta release (MiSTer as a priority platform)

* July: public release

This time I will send a link to the beta release to $3+ patrons privately. The beta files will not be attached to the post as before.

This core was the request of one director patron and I am happy ...

1943 Public Release: MiSTer

Sorry for the long wait. The public version of 1943 for MiSTer is finally here. Thanks a lot to all patrons. This is the first version for Avatars in the pause screen. I think they are really cute!

Remember that you have to press both fire buttons to perform a loop.

Please find the file attached. I think you should be able to get it through the usual MiSTer automatic update script too.

Update on the Status of 1943 for MiSTer

About 10 days ago I released 1943 for MiST, but I know most of you want the MiSTer version. However, the port didn't go as expected, why?

MiST FPGA can work well with different circuits operating inside it at different clock speeds. The MiST SDRAM chip is also relatively close to the FPGA and that makes it more reliable. It was easy to get MiST to work at 106 MHz for SDRAM access while the core itself was running at just 12MHz.

For MiSTer the situation is an FPGA that doesn't like jumping from on...

1943 Public Release (Part 1)

Sorry for the delay. The preparation of the release files has been harder than expected. I develop everything on MiST and I run trials without sound for faster compilation. When I added sound to make the release files I ran into memory problems because of the pause screen avatars. I spent two days trying to work around it but I finally gave up on the avatars for the MiST version on this core -at least for now. Avatars will be present in the MiSTer version, which is the mainstream one. (MiSTer's FPGA has more RAM built in)

When I moved ...

1943 Pause Screen

Last weekend I completed the 1943 core pause screen with patrons on $10+ tiers. For the first time, the pause screen includes avatars of $20+ patrons. It has been very interesting to convert the images to the arcade format. Remember that the pause screen is rendered using the arcade GPU. I basically disconnect it partially from the CPU -which I leave halted- and connect it to an alternative video memory.

I originally thought of this as a way to give recognition to patrons but it has turned out to be a ...

Real Audio Tape on 8-bit CPU cores

I have written a module which once added to the 8-bit CPU cores (Spectrum, Amstrad, Commodore, Atari...) will enable direct tape connection to the MiSTer board. I mean, an actual tape or other audio source. Now other people are looking into finishing this, with proper support in the MiSTer framework and I/O boards to connect to it.

YM2160 is also ready. Maybe it will need some debugging, but it is pretty much done.

So I am moving now to preparing the release of 1943 arcade core with all the names...