Shaggy the Atarian Posted October 27, 2004 Share Posted October 27, 2004 Once again I just want to ask about the possiblity of maybe recreating the 16k RAM Module that Curt has and maybe adding on a POKEY chip and perhaps more than 16k? Would anyone who is good with hardware consider that a worthwhile project? I've always wondered why they put so little RAM on the 7800. 4k seemed so small even by 84 standards... Quote Link to comment Share on other sites More sharing options...
Bryan Posted October 27, 2004 Share Posted October 27, 2004 I've always wondered why they put so little RAM on the 7800. 4k seemed so small even by 84 standards... ANTIC has refresh circuitry for DRAM but since Maria has no such capability, more expensive SRAM was the only option. This isn't usually a problem since you can store your graphics in the cartridge. It can be a problem for any game which requires large bitmaps, however. -Bry Quote Link to comment Share on other sites More sharing options...
Shaggy the Atarian Posted October 27, 2004 Share Posted October 27, 2004 I've always wondered why they put so little RAM on the 7800. 4k seemed so small even by 84 standards... ANTIC has refresh circuitry for DRAM but since Maria has no such capability, more expensive SRAM was the only option. This isn't usually a problem since you can store your graphics in the cartridge. It can be a problem for any game which requires large bitmaps, however. -Bry I see, thanks for answering that. So what did they do for Midnight Mutants and it's bitmaps? Put extra RAM on the cartridge? Quote Link to comment Share on other sites More sharing options...
Bryan Posted October 27, 2004 Share Posted October 27, 2004 I see, thanks for answering that. So what did they do for Midnight Mutants and it's bitmaps? Put extra RAM on the cartridge? Well, you can have large bitmaps in the cartridge, but you can't alter them (so it would be difficult to do something like a paint program). You can move other sprites on top of them, though. -Bry Quote Link to comment Share on other sites More sharing options...
kenfused Posted October 28, 2004 Author Share Posted October 28, 2004 There is also indirect graphics (ala character set graphics) which can be used to save memory and processing. For instance, in Beef Drop, currently the background is using indirect mode, 2 byte wide characters with 4 bit color. Essentially my background and burger part processing logic is unchanged from the 5200 version except I have to double all of the character values because they are two byte wide characters (which makes them 4x8 pixels just like the 5200 version...but have more color). The only thing bad about character set graphics is you are limited to 256 characters. Display list interupts can be used like on the 8-bit though (as my current Beef Drop implementation does after the score area to switch colors, character sets, and to switch from 320 mode to 160. Quote Link to comment Share on other sites More sharing options...
Shannon Posted October 28, 2004 Share Posted October 28, 2004 hmmm sounds like the 7800's display method is pretty fucked up and not much better than the 2600 method (except for maybe in speed?) Quote Link to comment Share on other sites More sharing options...
kenfused Posted October 28, 2004 Author Share Posted October 28, 2004 Little more progress. A few issues to resolve, like it running slow when there are more objects on the screen. So far, no pepper and no death. bd7800.zip Quote Link to comment Share on other sites More sharing options...
Shaggy the Atarian Posted October 28, 2004 Share Posted October 28, 2004 Little more progress. A few issues to resolve, like it running slow when there are more objects on the screen. So far, no pepper and no death. It just gets better every time you release one of these. To me it didn't seem like it was slowing down as much as with the first demo you posted here. Keep up the great work! Quote Link to comment Share on other sites More sharing options...
gdement Posted October 28, 2004 Share Posted October 28, 2004 hmmm sounds like the 7800's display method is pretty fucked up and not much better than the 2600 method (except for maybe in speed?) No way. It's just a little lower-level than some other systems. A real TV draws the screen line by line, so its nice that the maria lets you exploit this - hence the ability to change resolutions or color settings mid-screen. Other systems force you to treat the entire screen as if it gets blitted all at once - and that's really an artificial simplification. I don't think it's any harder to program, once you set up the display lists the maria will draw each scanline without intervention. The display lists have the same effect as raster memory, they're just scanline oriented. Quote Link to comment Share on other sites More sharing options...
Bryan Posted October 28, 2004 Share Posted October 28, 2004 The Jaguar generates the display in a similar way (object list), just wth a lot more bells a whistles. -Bry Quote Link to comment Share on other sites More sharing options...
EricBall Posted October 28, 2004 Share Posted October 28, 2004 hmmm sounds like the 7800's display method is pretty fucked up and not much better than the 2600 method (except for maybe in speed?) I wouldn't be that harsh; it's simply different. And there are some 7800 games which put it's capabilities to good use, so obviously it isn't that bad. You can't compare the graphics capabilities of the 2600 with the 7800. A 2600 game is like a one-armed paper-hanger, trying to update the TIA registers ahead of the scanline. On the 2600 the CPU does all the work, while on the 7800 the CPU sets up the display lists and stands back. Sure, you can use a DLI to update a register or two during the frame, but for the most part the CPU isn't involved with the graphics. It's a different paradigm. It's like older FPS which had software 3-D renderers and modern ones which use OpenGL or D3D and pass off the rendering (in the form of lists) to the GPU. Quote Link to comment Share on other sites More sharing options...
Bruce Tomlin Posted October 28, 2004 Share Posted October 28, 2004 If there's any negative about the way the 7800 works, it's that the Maria steals a lot of CPU time with its DMA. The NES doesn't have this problem, because the graphics chip gets its own separate RAM and ROM. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 28, 2004 Share Posted October 28, 2004 Well Ken, This newer build is excellent! I still wish it didin't look sooo much like the 5200 version since I know the 7800 can produce better graphics. Still, this is pretty much the furthest I have seen any 7800 homebrew get and this is really quite exciting! I wish it actually didn't use a Pokey, only because the Pokeys aren't unlimited in their supply. We have lots of BallBlazers avail thus far...but if more 7800 homebrews use the Pokey...it could become nasty trying to get the chips. I assume the game will function without a Pokey? But just not have sound? Or only have limited sound? Is there a way to have sound generated by both the TIA and the Pokey? That way you could setup an alternate sound system that would sound good, minus the music perhaps? This does play way way way too fast in MESS but then you knew that already. It is really quite impressive to see how far you have come in this in sooo little time. You do know that you have to do new homebrew ports of Moon Patrol and Crystal Castles now...right? I would use the 5200 versions as the models...but increase the graphics. The graphics of the 8-bit Crystal Castles looks good..but need more colors... Now we need Joe to design a 7800 PCB for these homebrews. I have a feeling that Ken is having fun with this BD port he is doing, and might just try to do a few more? Quote Link to comment Share on other sites More sharing options...
ubersaurus Posted October 28, 2004 Share Posted October 28, 2004 Well, to be fair, 2600 Burgertime's sound wasn't too bad...you could use something like that did. Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 28, 2004 Share Posted October 28, 2004 Good point Uber... It even had the music...go figure... But imagine the Moon Patrol theme done even better with a Pokey and with better graphics on the 7800?! Oh yeah....hehe... Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 28, 2004 Share Posted October 28, 2004 Is there a way to have sound generated by both the TIA and the Pokey? That way you could setup an alternate sound system that would sound good, minus the music perhaps? Commando actually does it this way, TIA handles the sound effects and POKEY the music. Beef Drop appears to use the Pokey for all the sound, same as Ballblazer. Mitch Quote Link to comment Share on other sites More sharing options...
+-^CrossBow^- Posted October 28, 2004 Share Posted October 28, 2004 You Mitch that makes sense. Because Commando's music still doesn't play even in the latest version of Mess. And BallBlazer is still missing the counter melody that plays during the main theme. So the Pokey emulation in MESS while good and seems to work great for this port of BD...still isn't quite right with actual released titles that used it. Maybe Ken can create a method whereby the difficulty switches can turn on music for the TIA only..or switch to the Pokey? Kinda like how 2600 Moon patrol switches the music on and off via Diff switches? Or...Ken might be able to set it up so that it always plays the pokey music if the music is present, but if you switch a Diff switch, it will play the TIA version? That way, if you can't get a Pokey or if an option to buy the game with or without the Pokey were avail, there would still be an option for music? Personally, I would rather see BD done in some new Red colored translucent case that snaps together without a screw. That way, I can remove the board and perhaps add a pokey to it at a later time. That could be an option to keep BallBlazers from just getting bought to be gutted for the Pokeys and keep the cost of the cart down production wise. Damn...starting to sound like J. Tramiel again...ugh...scary... Quote Link to comment Share on other sites More sharing options...
ubersaurus Posted October 28, 2004 Share Posted October 28, 2004 I'd just cut the POKEY out altogether. It drives up cost for a game that, in all honesty, is perfectly fine without it (as the 2600 Burgertime proves). I could see the Burgertime music playing with just the 2 sound channels, with one interrupting the music for sound effects when you're throwing pepper or stepping on a bun. I mean, look at it this way-POKEYs are 5 bucks from Best, and they are in a limited supply. You can hack em out of Ballblazers and probably busted 5200s, but again, thats still at least 5 bucks, probably more. And if you're gonna have to drive the price up for the game, I'd say go with extra RAM, so you can put in all the stuff you wanted in it. Just my thoughts-I'm not the programmer, so obviously I don't have the final say. I do like the idea of having the POKEY optional that the game's owner can put in themself if they really want to, but that may be a little too much. Quote Link to comment Share on other sites More sharing options...
mvigor Posted October 28, 2004 Share Posted October 28, 2004 Ok no. Include an empty low profile socket onboard, but for goodness sake don't exclude the Pokey if you have the ability to take advantage of it. Think of all the CC2 owners. Quote Link to comment Share on other sites More sharing options...
gdement Posted October 29, 2004 Share Posted October 29, 2004 If there's any negative about the way the 7800 works, it's that the Maria steals a lot of CPU time with its DMA. The NES doesn't have this problem, because the graphics chip gets its own separate RAM and ROM. That's true. It would be nice if they had either set up some dedicated maria memory or else just used a faster version of the 6502, whichever solution was cheaper. Quote Link to comment Share on other sites More sharing options...
gdement Posted October 29, 2004 Share Posted October 29, 2004 You Mitch that makes sense. Because Commando's music still doesn't play even in the latest version of Mess. I believe my commando file came from AtariAge, and after looking elsewhere I still wasn't able to find one that had working sound. I looked into it and realized the .a78 header is all that's wrong. I forget which byte it is, but the POKEY flag isn't set. The erroneous byte was set for 02, and it should be 03. It's a simple fix if you have a hex editor. After setting the flag the music works fine in MESS. Quote Link to comment Share on other sites More sharing options...
+Mitch Posted October 29, 2004 Share Posted October 29, 2004 You Mitch that makes sense. Because Commando's music still doesn't play even in the latest version of Mess. I believe my commando file came from AtariAge, and after looking elsewhere I still wasn't able to find one that had working sound. I looked into it and realized the .a78 header is all that's wrong. I forget which byte it is, but the POKEY flag isn't set. The erroneous byte was set for 02, and it should be 03. It's a simple fix if you have a hex editor. After setting the flag the music works fine in MESS. Yeah, there is a 7800 Commando ROM floating around with the wrong header. You can download the correct one from my web site. Mitch Quote Link to comment Share on other sites More sharing options...
kenfused Posted October 29, 2004 Author Share Posted October 29, 2004 The game mostly just uses a Pokey currently because I was able to directly copy the code from the 5200 version. I thought about making it try to detect the POKEY, and adjust accordingly....but then some probably wouldnt want a cart and just run it on a CC2. Are there any other cheap and simple sound chips that are plentiful in supply and could be added to a custom circuit board. Of course then, it would loose its Atariness in sound. Note currently also, I am using POKEY's RANDOM register until I drop in a random number function. Graphics will probably eventually get a facelift for the objects. If you played any of the demo, I havent even added more color to all of the pickle objects yet so it looks really bad. Unfornately we do not have any better resolution, but having more color available should help some. . Quote Link to comment Share on other sites More sharing options...
kenfused Posted October 29, 2004 Author Share Posted October 29, 2004 minor updates. No longer relies on POKEY for random numbers. You can now die. Life and Level display. Some speed optimization. It still slows down with more enemies so I need to find a way to keep the speed constant, No pepper yet. I also seem to be doing something reading the fire buttons and need to figure out how to read the start, reset, and pause switches. I am guessing that would be covered in 2600 doc (and PAUSE is like the B&W switch I think?). bd7800a.zip Quote Link to comment Share on other sites More sharing options...
Albert Posted October 29, 2004 Share Posted October 29, 2004 Maybe this thread should be renamed? ..Al Quote Link to comment Share on other sites More sharing options...
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