Curt Vendel Posted December 2, 2011 Author Share Posted December 2, 2011 It's posted... 1 Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 6, 2011 Author Share Posted December 6, 2011 Just a quick update, Mark is doublechecking my changes to the schematics and PC Board layouts, I'm testing a change to the audio summation circuit tonight to improve compatibility with Pokey equipped cartridges and also to smooth out the sound from the XM pokey a bit. We've moved up to an 84 pin CPLD because of the need for a lot more I/O lines as we've separated the Bus lines to add better handling of the devices and also better control and compatibility overall. Mark also needed more room to implement some additional logic he's added. I am hoping to run off the new boards very shortly, but I am gonna have to say, most likely the only ones seeing an XM under the tree are going to be Mark and Bob and maybe one other developer for short term and as long as everything is fully shaken out and we are all confident of the functioning of the latest design updates, then I'll make another run of PC boards and start assembling again. Curt Link to comment Share on other sites More sharing options...
Dino Posted December 6, 2011 Share Posted December 6, 2011 Curt, I think its better to take your time and get it right than trying to rushj it our for christmas and getting it wrong... 1 Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 6, 2011 Author Share Posted December 6, 2011 Well, I was kinda hoping to get a bunch out for the holidays to people, so I'm a little disappointed, but I just don't want to take any chances, we are into the home stretch, a heck of lot of timing issues have been fixed and some new changes to make the hardware run better have been put in, we added about $6 worth of new parts in total into the design, but it is, what it is and this needs to be right out of the gate... I don't want 14 months of hard work and everyones support to be ruined by rushing these last couple of checks and such... I have to thank Mark a lot for that too as there have been a few times I've wanted to run another set of boards and he's asked me to wait until some other things were signed off, and its been a good thing too as some addition changes did need to be made. Curt 3 Link to comment Share on other sites More sharing options...
HARMIK Posted December 6, 2011 Share Posted December 6, 2011 Please take your time would hate for some bug to creep in at this point. And I've said it before but I don't think it can be said enough thank you to all involved for there hard work. 1 Link to comment Share on other sites More sharing options...
Lendorien Posted December 6, 2011 Share Posted December 6, 2011 I would say that if anyone knows what the XM boards need in revisions, it's likely be Groovybee, the one who has worked most closely with programming on the thing. None of us want to keep waiting for this to come out, but I trust his judgement, since he's the programmer who knows it best. 2 Link to comment Share on other sites More sharing options...
bradjewell Posted December 6, 2011 Share Posted December 6, 2011 Nothings better than that awesome christmas gift that comes a little later.... Take your time and have yourself a good christmas and get out the best quality product you can... 1 Link to comment Share on other sites More sharing options...
JonnyBritish Posted December 6, 2011 Share Posted December 6, 2011 Actually a relief the XM will not be out for christmas..now i will be able to afford presents for the family rather than spending all my money on XM games 1 Link to comment Share on other sites More sharing options...
+swlovinist Posted December 7, 2011 Share Posted December 7, 2011 Take your time, no rush. I'll be happy to wait longer for a more refined product. Thanks for the updates. Link to comment Share on other sites More sharing options...
Madaracs Posted December 7, 2011 Share Posted December 7, 2011 I hear this thing will make breakfast and take out the trash too. Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 7, 2011 Author Share Posted December 7, 2011 Only if you code the games to take advantage of the additional breakfast and garbage disposal ports We had the kitchen sink originally spec'd, but needed to make room for the PIA chip, so we took it out.... I hear this thing will make breakfast and take out the trash too. 2 Link to comment Share on other sites More sharing options...
Lendorien Posted December 7, 2011 Share Posted December 7, 2011 Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. Link to comment Share on other sites More sharing options...
DracIsBack Posted December 7, 2011 Share Posted December 7, 2011 Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. I don't think it's possible at all. IIRC, the 7800 has a 2600 mode and a 7800 mode. If it doesn't find the validation key, it thinks it's a 2600 and essentially part of the hardware doesn't even turn on. It uses TIA for graphics for example, while MARIA is dormant. Once it find the validation key, it's a "7800" and uses MARIA for graphics. Link to comment Share on other sites More sharing options...
atarian63 Posted December 8, 2011 Share Posted December 8, 2011 I want my XM thing (sung to the tune of "I want my MTV") Link to comment Share on other sites More sharing options...
desiv Posted December 8, 2011 Share Posted December 8, 2011 We had the kitchen sink originally spec'd, but needed to make room for the PIA chip, so we took it out.... As long as you left the solder pads in, so we can hack it back in.... :-) desiv Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 8, 2011 Author Share Posted December 8, 2011 The problem lies in the fact that 2600 cart's don't have the needed address lines, nor do they have a r/w line, clock line or an external audio line.... if they did, they'd be 7800 carts :-) Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. Link to comment Share on other sites More sharing options...
Wickeycolumbus Posted December 8, 2011 Share Posted December 8, 2011 The problem lies in the fact that 2600 cart's don't have the needed address lines, nor do they have a r/w line, clock line or an external audio line.... if they did, they'd be 7800 carts :-) Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. What would stop the program from accessing XM (or any 7800) RAM though? Isn't that how Save Mary for the 7800 works? Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 8, 2011 Author Share Posted December 8, 2011 The problem lies in the fact that 2600 cart's don't have the needed address lines, nor do they have a r/w line, clock line or an external audio line.... if they did, they'd be 7800 carts :-) The XM Ram is controlled through RAM access lines from the MARIA, the system would have to be in 7800 mode and MARIA active to enable the RAM1 and RAM0 enable lines, plus you would still need address lines A13-A15 to engage the needed logic for just the RAM_CS and one of the the key Address lines going into the XMRAM, lastly... you still don't have a R/W line from a 2600 cart to the 7800 or the XM, this is not ROM loading memory, this is actually game RAM that the game needs to write into and use, so no a 2600 cartridge is not going to be able to use the extra RAM space. Curt Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. What would stop the program from accessing XM (or any 7800) RAM though? Isn't that how Save Mary for the 7800 works? Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 8, 2011 Author Share Posted December 8, 2011 Sorry, you mentioned Save Mary.... That was some kind of funky hack where a 2600 game was slightly changed so it could access the 7800 ram instead of the Sara chip, right? I don't fully know the deal with that game but wasn't it put on a 7800 board and some code was altered to somehow put the 7800 into Maria mode... Hopefully someone fully familiar can explain more because without the 7800 being in Maria mode and the ram0/1 lines from the Maria being active, I'm not sure how it's going to accomplish this without a neat but clean kludge Link to comment Share on other sites More sharing options...
alex_79 Posted December 8, 2011 Share Posted December 8, 2011 (edited) AFAIK Video61 Save Mary has its own ram chip on the cartridge. This was much easier on the 7800 because of the read/write and clock signals on the cart port; moreover the full address bus of the 6502 allowed to run the game (which is 16k) in the linear memory of the 7800, without bankswitching logic. http://www.atariage....post__p__773066 http://www.atariage....post__p__139381 Edited December 8, 2011 by alex_79 Link to comment Share on other sites More sharing options...
Curt Vendel Posted December 8, 2011 Author Share Posted December 8, 2011 That makes a lot more sense.... I didn't see quite how they could accomplish accessing the 7800 Memory, since again, they would've had to have enabled the MARIA to control its RAM0 and RAM1 lines.... yes, having the 6502 in there vs the 6507 is certainly a nice additional advangtage. AFAIK Video61 Save Mary has its own ram chip on the cartridge. This was much easier on the 7800 because of the read/write and clock signals on the cart port; moreover the full address bus of the 6502 allowed to run the game (which is 16k) in the linear memory of the 7800, without bankswitching logic. http://www.atariage....post__p__773066 http://www.atariage....post__p__139381 Link to comment Share on other sites More sharing options...
GroovyBee Posted December 10, 2011 Share Posted December 10, 2011 Here's a curious question from someone who's dumb about such things. Would it be possible to program an atari 2600 game to use features of the XM, such as RAM or sound options? I understand that things would be limited by CPU cycles, but I'm still curious. The XM control registers and peripherals are mapped into the $45x to $47x address range so should be accessible in 2600 mode. You could enable RAM and access an 8K page at $4000 to $5FFF (MARIA takes into account A14 and A15 in 2600 mode). You couldn't access an 8K page at $6000 because A13 would then be high which would normally cause the 2600 ROM to be accessed (or you copy a 4K image from ROM to RAM to ensure that reads don't conflict the data bus). Normal lda $xxxx and sta $xxxx instructions should work fine on XM RAM in the range $4000 to $5FFF. The XM mappers rely on HALT# so they won't work in 2600 mode. POKEY audio will need "detuning" compared to normal usage because of the lower CPU clock in 2600 mode. YM2151 audio will work fine (it has its own clock). Obviously this is all theory because I haven't tested it in 2600 mode. I'm probably not going to test it from 2600 code either since it is a 7800 mode peripheral. Link to comment Share on other sites More sharing options...
Eckhard Stolberg Posted December 10, 2011 Share Posted December 10, 2011 I don't think accessing XM RAM would be possible like this for a 2600 cart. The 2600 only has an address space of 8K total with the first 4K being used by the TIA and PIA and the second 4K being used by the game ROM. IIRC this is true for the 7800 in 2600 mode too. So all XM RAM would either conflict with a mirror of either the TIA/PIA or the ROM. It might be possible to access RAM at $5000-$5fff and $7000-$7fff (can the XM map it's RAM there?) if you'd put the 2600 game on a 7800 board. I think the hacked version of Save Mary does something similar, but uses it's own RAM on a 7800 board. Link to comment Share on other sites More sharing options...
GroovyBee Posted December 10, 2011 Share Posted December 10, 2011 Apologies for the RAM access mistakes in my previous post (I blame a distinct lack of tea ). We know the following :- - When the 7800 BIOS detects that there is a 2600 cart in the slot the last thing it does before handing control over to the cart's reset vector is to write $FD to the latch. This locks into 2800 mode, enables A12, A14 and A15 to it's cart slot and sets MEN low on MARIA. - MARIA decodes MEN low and A12 low to access TIA/RIOT depending on if A7 is low/high. Address lines A13 to A15 are don't care. - XM can map an 8K page at $4000 and another 8K page at $6000. Since A12 is low in both cases MARIA will decode a TIA/RIOT access for memory accesses in the range $4000 to $4FFF and $6000 to $6FFF. - When you access XM RAM locations $5000 to $5FFF and $7000 to $7FFF address line A12 is high so both the ROM on a 2600 cart and the XM will be read/written simultaneously (unless you have a new bank switching scheme). In conclusion XM RAM won't be accessible in 2600 mode. Link to comment Share on other sites More sharing options...
killersquirel Posted December 13, 2011 Share Posted December 13, 2011 Quick! Somebody get this man some tea! Link to comment Share on other sites More sharing options...
Like us on Facebook
Follow us on Twitter
AtariAge on Instagram
Watch us on YouTube
Chat on Discord
Recommended Posts