MT> How did your history of programming on the Commodore computers assist you with Atari development?
DS> I started learning BASIC on a Commodore PET my freshman year of high school in 1980. I received a VIC 20 for Christmas in 1981 and soon after ran into speed and program size issues with BASIC and only 3.5K of RAM (the VIC had 5K of RAM, but 1.5K was used for video RAM and other system needs). The VIC's Programmer's Reference Guide had a section on Machine Language so I started writing small subroutines, such as scrolling the entire screen sideways, that could be utilized by a BASIC program (in this instance a Super Cobra inspired game). Over time I wrote more complex games as well as BBS and terminal software for the VIC 20, Commodore 64 and 128.

The VCS uses a 6507 CPU, which is fundamentally the same as the 6502 CPU used in Commodore's home computers, so when I decided to write a game for the VCS I already had the machine language down and only needed to learn the specifics of the VCS's hardware.

MT> Tell us about yourself?        
DS> I was an Army Brat, thus moved around a lot as a kid. We kept moving even after dad left the military - when I was 25 I figured out that I'd moved an average of once a year. I moved to Houston in '87 to attend the University of Houston and liked the city so much that I've stayed. I currently work for Spacedesign on software that's used to design spacecraft. Prior to that I did custom modifications to ERP systems at a couple manufacturing companies.

MT> What other interests or hobbies do you share other then retro gaming?
DS> I love to read, mostly sci-fi and fantasy. I've also been into home theater for quite a while - my initially setup was a 27" TV with Dolby surround sound and a laser disk player, my current setup is a 65" HDTV with 5.1 surround sound and Blu-Ray via my PS3. Besides retro gaming I'm also into modern gaming on the PS3, PSP, iPhone and my Mac. I'm seriously looking forward to Blizzard's forthcoming StarCraft II. While visiting my brother last summer, I introduced my nephew Justin to the original StarCraft. We play each other online quite a bit, and my dad's even joined us for a few games. It's pretty cool as we're scattered across the continent - my nephew's in Wisconsin while my folks currently reside in Mexico due to my dad's job.

MT> Why the love for the VCS?
DS> We had one growing up and I had fond memories of playing games like Adventure, Kaboom!, Space Invaders and Warlords . I'd gotten away from the VCS in the '80s when I started gaming and programming on the Commodore computers. I got back into the VCS in 1996 when I ported Stella to OS/2.

MT> First, what happened to 'Dragon Defense Squad'?
         Will we ever be able to foil the evil wizard's plans and save our crops!?
DS> Soon after I started working DDS the economy took a hit. The company I worked for at the time went through a number of layoffs and then a cross-the-board paycut. I lost 20% of my income, so I picked up a side job to help make ends meet. This resulted in DDS being put on the back burner. I plan to resume work on it, but don't know when it will happen..

MT> …and 'Rally S'?
DS>I program for a living and, as happens from time to time, I got a little burned out of coding soon after starting on Rally S. I started getting back into it when I was invited by AtariAge to be part of their annual Holiday Cartridge and ended up working on Stay Frosty instead. Like DDS, I still plan to do it but don't know when.

MT> Why is 'Medieval Mayhem' so much better than the original 'Warlords' for the Atari VCS?
DS> I think the main thing is that nowadays ROM is cheap. Carla Meninsky only had 4K of ROM to work with for Warlords, and she utilized it to the fullest. In contrast, Medieval Mayhem uses 32K, of which 6K alone is used for the main menu. Having additional ROM made it possible to add features from the arcade version that could not be squeezed into a 4K game.

MT> During development of 'Medieval Mayhem', did you ever find yourself banging your head against the wall, as the Atari is so difficult to program? What obstacles did you have to surpass to make a better 'Warlords" during the nine month project?
DS> Numerous times, there's three main issues with coding for the Atari - RAM, Processing Time and Video Output.

The Atari has 128 bytes of RAM - not megabytes, not kilobytes, just bytes. During development I frequently ran out of RAM and had to revise how the game was utilizing memory. One way to save RAM is to combine multiple variables into a single byte by using specific bits within the byte. An example of this is a single byte stores the settings for Castle Hit Flash, King Hit Flash, Game Speed and Maximum Fireballs as well as keeping track of the game state(is the menu, demo game, or active game showing). Another way is to repurpose bytes so they mean different things in different parts of the program. An example of that is the RAM used to draw the Main Menu is the same RAM used to draw the castle bricks during the game.

Processing Time and Video Output issues go hand-in-hand. TIA, the Atari's video chip, doesn't have Video RAM, so the CPU must update TIA in real time to draw the display. There's 262 scan lines in an NTSC TV picture, of which 200 comprise the visible portion of the screen; so, after drawing the screen, there's less than 24% of the CPU time remaining for game logic. To make matters worse, a TV sync signal must be triggered at a specific time in the middle of the non-visible 62 scan lines - if it's sent at the wrong time the display will visibly jump or jitter. One of the last bugs I tracked down was a rare occurrence of screen jitter during the Attract Mode.

MT> Technically, the Atari VCS is a 4KB memory machine. Explain to those unfamiliar, how you used "Bank-Switching" technique to inflate the available memory for 'Medieval Mayhem'?
DS> There's special hardware in the cartridge that handles the bank-switching. The version I used takes the 32K of ROM and chops it up into 8 banks, each containing 4K of the program. The bank-switching hardware monitors the program's access to "trigger locations" that tell the cartridge to change which of the 8 banks the CPU is looking it. This is similar to a book and how you turn the pages to read different parts of it.

MT> 'Medieval Mayhem' was not a single person project. Who else assisted in this great game?
DS> David Vazquez did the Dragon, Knight and King graphics. He also came up with the idea for the Marching Knight intermission, I was originally going to show a trophy at the end of each round. Erik Ehrling did the title screen music using Paul Slocum's Music Kit 2.0. There was also a lot of feedback provided by the forum members at AtariAge which resulted in the game being much better than if I'd developed it "behind closed doors". One of those suggestions was the texture on the bricks, which really enhances the appearance of the game. One of the two Easter Eggs in Medieval Mayhem lists all the people who helped out in some way.

MT> Those in the know, recognize that the VCS is capable of displaying only a few sprites on-screen simultaneously.
         How did you "trick" the machine to get past the 2 sprite, 2 missile, single ball and background limitations?
DS> When the Atari was designed the original idea was for the program to horizontally position the objects when the screen wasn't being drawn. Programmers discovered very early on (as seen in Air-Sea Battle, one of the original nine Atari games) that the objects could be repositioned while the screen was being drawn. The only side effect is a short black bar appears on the left edge of the screen on the scan lines that the repositioning occurs on. The black bars aren't very noticeable in Medieval Mayhem as the screen is black, though they are visible when the screen flashes.

MT> 'Medieval Mayhem' was well received by Atari homebrew community. How does it feel to have your labor of love recognized?
DS> It's been extremely gratifying. One thing that really surprised me is Medieval Mayhem has been used in competitions at retro gaming events, such as Retro GC's AC 2008 in France.

MT> Did you ever daydream as a child about making your own VCS game?
Yes I did, though it was pretty much satisfied when I got my VIC 20 and I was able to write games on it. What inspired Medieval Mayhem was playing Warlords on the Atari with my nephews and their friends when I visited my brother for Christmas of 2005.

MT> 'Stay Frosty' was a true highlight of the past holiday cart. 32 levels in 12K! Truly an impressive feat for having only a two month of development window. Ever thought of making Frosty a full solo title or was it truly over when Frosty melted away?
DS> Thanks! Nathan Strum came up with the basic game idea, as well as designed all of the graphics. There was a lot more we wanted to do with Stay Frosty, but couldn't due to the limited time and ROM space. We've discussed the possibility of a stand-alone sequel and I've already converted the program to a 32K binary in preparation for it.

MT> So, what's next?
DS> I'm learning Cocoa Programming so I can write a Mac interface for the AtariVox. I'd like to utilize the AtariVox in some fashion in the afore mentioned sequel.

Thanks for the interest!

Darrell, many of us reading your interview now envy your lifestyle (sigh)
We truly appreciate your efforts and admire your wor - THANKS!

If you have questions for Darrell,
you may e-mail him at: darrell.spice.jr@spiceware.org

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