Porchy

Black Tiger repair log #4

Feb 282019

I got the same Black Tiger bootleg board back as in my repair log #3.

The sound had stopped working completely.
I did all the usual visual checks and reseating where I could but no joy.
I probed the Z80 CPU and found following a brief flicker at power on the /HALT pin was always asserted. I pulled the ROM and checked it in my programmer but it came back as good. There is nothing in the way of buffering in between the CPU and ROM.
I decided the quickest way to see what was happening here was to attach the logic analyser to the CPU address bus with the trigger set to the /M1 signal.

From here I could see that it started off good but failed when returning from a call. As the return address is pulled from the stack I decided to remove the RAM and test it. This turned out to be faulty reporting that bit 3 had become disconnected.
Replacing the RAM brought the sound back.

BINman program update

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Jan 022019

Today I’ve uploaded the latest version of my BINman software.
This version is v4.3.2 and has had some rewrites and a few extra features added.
First is the ability to deinterleave the bytes of a file into nibbles.
Second feature added can be found under the “Special” menu. It was added as a request from a user. This swaps the nibble values from one byte and the adjacent byte then deinterleaves that file. For example an original file of: “12 34 AB CD” will output two files, one containing “13 AC”, the other “24 BD”.
Its not something I’ve ever had the need for but obviously someone wanted it so here it is.

As usual it can be found in the “Downloads/PC Software” section.

CK2605 Logic Diagram

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Nov 262018

While searching through some documents from Data I/O I came across a bunch of logic diagrams for various PLD’s. One of them was for the CK2605.
As I’ve not seen this in the wild before I thought I’d upload it.

*click the picture for PDF

Mortal Kombat II A-17480 PAL dump info

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Nov 012018

Some time back I bruteforced the A-17480 PAL16L8 chip from Mortal Kombat II. This was untested until recently when UKVAC member JonHughes tested it and found it didn’t work properly.
We tried several things but always got the same issues so he sent me his full PCB to do some testing of my own.
While I could find anything wrong from an operation point of view I did find that the original TIBPAL16L8-10 PAL chip transitioned states about 4ns faster than the fastest GAL chip I have to hand. I had experimented with GAL’s ranging from 10 to 25ns but the slower ones did just make the issue worse.
In desperation I ordered a NOS TIBPAL16L8-10 from eBay (not too cheap these days) in order to be 100% sure of my work. The result was a perfectly running game.

So what are the issues? Well not a lot really. A GAL substitute will still allow the game to play very well but it did show errors during the POST

The game itself also plays fine but there are some graphical issues here and there, most noticeably on the ground during actual gameplay.
On the video you can see the ground keeps glitching black. This is pretty much the only fault I can see but its definitely worth noting

The video is not the best quality, capturing CRT screens with my phone is never great but hopefully you can see.

Decrypted SEGA files removed!

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Oct 272018

Due to certain things that have been going on elsewhere on the internet I have made the decision to remove the SEGA ROM’s from this site.
I have not personally been asked to take these down but given what I’ve seen happen recently involving SEGA ROM’s and previously with Nintendo too I thought I would play it safe and remove these files.

Sorry for any inconvenience

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