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Messages - DarrenColes

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CODING AREA / Re: A couple of games in BASIC I worked on recently.
« on: June 03, 2019, 04:37:27 PM »
here are a few screenshots (of the 2k one) so you can see what it is without having to go to the effort of emulating or running on hardware.

CODING AREA / A couple of games in BASIC I worked on recently.
« on: May 29, 2019, 02:19:45 PM »
Some people on a discord channel I am on decided to have a go at writing some very small retro games in BASIC.

First off we decided to go with seeing what we could do in 1K. After I attempted that we agreed that 1K was probably a bit too limiting so we decided to go with 2K.

I decided BBC basic was a good bet since I know it pretty well. I have attached the two games as plain text in .bas files (including a fully commented, unoptimised version of the 1k one) and a disc image containing the games.

Obviously don't expect too much given the limitations but I was very pleased with the result of the 2K one.

RETRO SCENE OR GAMING NEWS . . . / Amiga Development System
« on: May 01, 2019, 04:19:01 PM »
Amiga Love has obtained an early Amiga Dev system (machines sent out to developers prior to the actual release of the 1000) and made a video about it.


A huge collection of Infocom’s Text Adventure games is now available in their source code form on Github. Thanks to Jason Scott efforts, 45 games are now at anyone’s reach to be dissected

CODING AREA / Acorn Electrom tape-to-disk conversion of Dujunz
« on: April 14, 2019, 03:13:50 PM »
Someone over on stardot forum was asking for a tape to disk conversion of the Acorn Electron version of Dunjunz.

I spent a few hours working on the conversion and managed to get it working without too much difficulty.

I decided to put together a guide to how the conversion was done.

IF you have a reasonable grasp of 6502 it should not be too difficult to understand.

One of my favourite sites Flashtro has web browser based remakes of many of those cracktros from (mostly) the amiga scene.

Not to condone piracy but those intros often held my interest for as long as the games themselves.

In addition if you are interested in the mechanics of how those games were cracked theres a whole load of tutorials to explain how it was done but you will need a good grasp of assembler to understand them.

They also are still releasing trainers for some of the more recent amiga releases.

RETRO SCENE OR GAMING NEWS . . . / Turrican 2 - The Final Fight cover
« on: April 10, 2019, 10:44:36 PM »
Banjo Guy Ollie takes on what is possibly one of the best and most well known Amiga tunes of all.

CODING AREA / Amiga cracktro/intro sourcecode & tutorials
« on: April 10, 2019, 11:31:03 AM »
Probably not for pure beginners, but if you have some assembly language experience and wanted to understand how some of the demo effects were done, there's lots of source code and tutorials here.

Much of it is reverse engineered rather than original code so not always the easiest to follow but interesting all the same.

CODING AREA / Kevin Edwards sourcecode
« on: April 10, 2019, 11:13:23 AM »
Kevin Edwards who worked on Galaforce and Crazee Rider for the BBC Micro and Acorn Electron has released the full source code to his games on github.

RETRO SCENE OR GAMING NEWS . . . / Antstream Kickstarter Now Live
« on: April 10, 2019, 10:57:18 AM »
AntStream is (supposed to be) the retro gaming equivalent to NetFlix.

The current licensed games list is..

Lots of Amiga, Spectrum, C64 and Arcade games.

Greetings Methanoid... Does your handle refer to Deuteros? That is probably my favourite game of all time.

CODING AREA / Re: Reverse Engineering a 6800 system
« on: July 12, 2018, 10:23:58 AM »
looks like you are progressing nicely.

Does anyone have any idea why there would be code that has two jumps one after the other to different addresses . The second can never be hit.

The only reason I can imagine you would see this would be if its a jump table accessed using indirect addressing so the disassembler didn't assign a label. I can't imagine why you could do this for only two values though as it would make more sense just to branch to the second one.

I can imagine you might end up with something like this if you were coding the equivalent of

switch (a)
   case 0:
   case 1:
   case 2:

;we enter here with value in A
TAB   ;copy A to B
ABA  ;A = A + B
ABA  ;A = A + B
STA A modify+1    ;self modifying code to update the JMP below
LDX #tablestart

 JMP 1111
 JMP 2222
 JMP 3333

CODING AREA / Re: Reverse Engineering a 6800 system
« on: July 03, 2018, 08:09:44 PM »
Cool. You really have been busy working out how it all goes together. I'd be interested to see the ROM dump you have. I have a reasonable understanding of how the kind of hardware used in olds systems like this but my skills really lie in the low level software side but I've not had much dealings with 6800. I've mainly worked in 6502 and 68000, some arm and sh2 and a bit of z80 for good measure.

If you were to continue posting your progress on here I for one would be very interested

CODING AREA / Re: Reverse Engineering a 6800 system
« on: July 02, 2018, 11:53:25 PM »
It is possible that the ROM's are mirrored at several locations by only doing partial address decoding, so for example the ROM could appear at 3000, 7000,B000 and F000 which would allow it to get the necessary values on reset.

CODING AREA / Re: Reverse Engineering a 6800 system
« on: July 01, 2018, 11:28:40 PM »
i  can't see anything wrong with any of your assumptions. Can you provide any additional details regarding the address space that the rom is mapped into and where it actually jumps to?

Is it possible that an interrupt might be kicking in and redirecting the execution to  one of the interrupt addresses FFF8/9 (IRQ), FFFA/B (SWI) OR FFFC/D (NMI)?

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