retrocanada76 Posted August 29, 2016 Share Posted August 29, 2016 (edited) Hi all, Since I cannot find any Axlon board to buy I decided to design my own Axlon compatible RAM board using 512KB Static RAM. I've designed some hardware for coco computers but for Atari that would be my first project. I've pretty much drawn the design: - It would sit in middle slot and I'd be pulling /S6 from OS-Board. - The static RAM would be disabled whenever /S2 and /S3 are high or /REF is low. - The bank register is a 4-bit flip-flop (I could make it 5 bit to use 512KB) - Power on reset would set the initial bank to 0 But I need to decide few details: - Should it use 0xCFxx or should I lock into 0xCFFF ? Which address does SDX use for BANKED ? - Should I care fro the shadow register 0x0Fxx or should avoid it at all ? - Should the bank be zeored in the reset ? If so, how axlon does that ? Does it pull the RES line from CPU ? - Should I use early R/W or late R/W signals ? Are all data and address lines set in the early ? Thanks, Edited August 29, 2016 by retrocanada76 1 Quote Link to comment Share on other sites More sharing options...
+Larry Posted August 29, 2016 Share Posted August 29, 2016 I have a 512k SRAM board for the 800. I think it is Axlon compatible. I'll dig it out tomorrow and take a look at the docs. I remember that it came with info on modifying Mydos for the big ramdisk. Larry Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted August 29, 2016 Author Share Posted August 29, 2016 Thanks, that would be helpful. Quote Link to comment Share on other sites More sharing options...
Mathy Posted August 29, 2016 Share Posted August 29, 2016 Hello Larry IIRC, Axlon support was fixed in MyDOS 4.55 beta 4. Sincerely Mathy Quote Link to comment Share on other sites More sharing options...
+Larry Posted August 29, 2016 Share Posted August 29, 2016 Here is a link www.bobhays.com/atari512k.html The docs and site don't actually say it is Axlon compatible, but perhaps you can tell for the other info provided. He did use Mydos 4.53/4 for this project. Larry Quote Link to comment Share on other sites More sharing options...
1050 Posted August 30, 2016 Share Posted August 30, 2016 - Should it use 0xCFxx or should I lock into 0xCFFF ? Which address does SDX use for BANKED ?Don't know about SDX at all. Axlon documentation suggests using 0xCFCx region while noting that this is actually the shadow of 0x0FCx which is the only address showing up at the slot used for a real Axlon board. 0x0FC0 thru 0x0FFF is the actual actuating locations with 0xCFC0 thru 0xCFFF being the shadow of that working location which also works the bank selection logic. - Should the bank be zeored in the reset ? If so, how axlon does that ? Does it pull the RES line from CPU ?No it does not have a RESET connection at all, most latches do however have a RESET function which can be combined with a capacitor/resistor pair to allow for a RESET pulse to exist after sufficient power on time has passed such that the latch is properly RESET - but not all latches are the same, some reset to zero, while others reset to all ones. And then latchless designs come along to defeat the proposed purpose entirely. In the case of the real Axlon it doesn't matter anyway since DOS is yet to be loaded and whatever the last byte is that is stored at 0x0FFF determines the 'home' bank anyway. An exceptionally stupid way to do it if you ask me, which I why I'm thinking bank 0 should be the 'home' bank since all size of Axlon would contain bank 0 while bank FF might be something nebulous depending on exact glue logic used and we really can't know this part universally, especially as to new designs. Software also an issue with FF for home banking on the Axlon, no universal standard exists or is adhered to that I'm aware of. Bank FF is the home bank for portB type ramdisks just as an aside. The 0xCFC0 thru 0xCFFF scheme is capable of (64) 16 meg ramdisks. Hardly a reason for such a beast to exist, the potential for it is still there. - Should I use early R/W or late R/W signals ? Are all data and address lines set in the early ? Concerning myself primarily with the software side, I have no opinion or experience to suggest anything here. The Bob Hays unit seems to break the rules at 0xEFxx region. Modified 4.53 MyDOS would be a modified version and only Bob and the lord knows what was modified there. Beta 4 MyDOS 4.55 has some Axlon code added in an attempt to correct the code such that it might work better - no testing was possible due to the rarity of real Axlon boards. But zero is stored to 0xCFFF in both DOS.SYS and the companion MyRD ramdisk program in an attempt to home bank with zero for Axlon detected ramdisks. http://www.mathyvannisselroy.nl/mydos.htm axlon_manual.zip 1 Quote Link to comment Share on other sites More sharing options...
sup8pdct Posted August 30, 2016 Share Posted August 30, 2016 I have superram 800. axlon compatiable. will try and do up a schematic for it sometime soon. Do know that bank select is $CFFF. James Quote Link to comment Share on other sites More sharing options...
+Larry Posted August 30, 2016 Share Posted August 30, 2016 And here is the modified MyDos 4.53/4. -Larry MyDos453 for 512K 800.ATR 1 Quote Link to comment Share on other sites More sharing options...
drac030 Posted August 30, 2016 Share Posted August 30, 2016 - Should it use 0xCFxx or should I lock into 0xCFFF ? Which address does SDX use for BANKED ? SDX uses $CFFF. Also the Antonia, when set in Axlon mode, reacts to writes to $CFFF (only). - Should I care fro the shadow register 0x0Fxx or should avoid it at all ? These do not seem to be used. SDX memory management skips that area when the 800 hardware was detected. Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted August 30, 2016 Author Share Posted August 30, 2016 This shadow register exists because Axlon doesn't pull the /S6 from OS-board (or /S0 from RAM1). So it never knows if the bank is S6 or S0. But it knows for sure that is not any of S2, S3, S4 and S5. The addresses 0xCFxx and 0x0Fxx have the same visible bits. I've simplified my design, I don't need to care about /REF anyway, just /S2 and /S3. Then I'll be using: 74LS04 74LS08 74LS138 74LS273 AS6C4008 - 512K SRAM I can easily add a power on reset on the octal flip-flop. It will be using 5-bits for 512K. Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted August 30, 2016 Author Share Posted August 30, 2016 The Bob Hays unit seems to break the rules at 0xEFxx region. That explains how he managed to use only 2 TTLs for the logic. I had to use 3 for the 0xCFxx range. 1 Quote Link to comment Share on other sites More sharing options...
sup8pdct Posted August 31, 2016 Share Posted August 31, 2016 Superram 800 uses the original chips on the ram card.The unwanted power tracks have been cut. Added chips are; 74LS573. Latch for $CFFF 74LS133 74LS158 x 2 74LS112 74LS27 James Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 3, 2016 Author Share Posted September 3, 2016 And it's ALIVE! I made a proto board to be used as ram or rom card. (the VCC is not connected). Anyway, it works really well I going to make a schematics for it. 512 KB fully Axlon compatible 0xCFC0 and no shadow register. Now my next challenge: make a OS-RAM card and maybe run 800XL rom. Also, I'm thinking adding Mr. Atari internal IDE 10 Quote Link to comment Share on other sites More sharing options...
Kyle22 Posted September 3, 2016 Share Posted September 3, 2016 Are there any of those proto boards for sale? Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 4, 2016 Author Share Posted September 4, 2016 Here the gerber files with few improvements I think was needed. Extra padding on edge connectors. You can order them from http://www.allpcb.com/it will cost you 15 dollars + 10 shipping depending where you are. You can choose to DHL express for 10 more (at least for me). I've submitted my files on Sunday night and got the boards by Friday afternoon, here in Canada. You can use the boards as ram or personality, since the VCC line is not connected, so you can route it as you want. Enjoy ATARI800-PROTOBOARD.zip 2 Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 4, 2016 Author Share Posted September 4, 2016 Osh park somehow doesn't like my excellon drill and the cost is pretty high because the boards are larger. Not recommended to use osh park when your boards get large. Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 4, 2016 Author Share Posted September 4, 2016 Here the schematics. It's pretty simple. First time I use KiCAD and I'm enjoying it Axlon 512.pdf 1 Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 5, 2016 Author Share Posted September 5, 2016 I made the entire board on KiCAD. Here the schematics, 3d view and gerber files if you want to produce your own. Axlon 512.zip Axlon 512.pdf 4 1 Quote Link to comment Share on other sites More sharing options...
a8isa1 Posted September 5, 2016 Share Posted September 5, 2016 Are a 16K board and a 32K board prerequisites for this upgrade? Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 5, 2016 Author Share Posted September 5, 2016 yes you need. This one goes in the middle slot and you still need the 16K on both 1 & 2 Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 5, 2016 Author Share Posted September 5, 2016 I have added a decoupling capacitor on SRAM. It's better this way. So use this version instead. Axlon 512.zip Axlon 512.pdf Quote Link to comment Share on other sites More sharing options...
ebiguy Posted September 5, 2016 Share Posted September 5, 2016 yes you need. This one goes in the middle slot and you still need the 16K on both 1 & 2 I guess many of us have the same idea when reading this thread: using some free slots to make new cards So, would it be possible to go a step further and - either make the middle board handle all the RAM (not only the middle 16KB). This will free at least the last slot. - or (better) make a single board for ROM (eprom) and RAM to replace the personality board. This will free 3 slots Because your proto board is great and if there were any slot free, one could try to build a different kind of extension to plug in the 800. In another thread about a 1090 expansion clone, someone gave a list of cards which could be created (can't find it right now). Why not try to build them for the 800. It would give the 800 the "open spirit" found in the Apple II. Am I the only one who is frustrated to not being able to use the slots for someting else than the ROM/RAM ? Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 5, 2016 Author Share Posted September 5, 2016 The middle board could have the slot3 ram on it, but not the slot1 because the signals needed are not there. But then it would require extra SRAM chip for the 16KB (the smaller I found was 32K SRAM). Trying to use a bank from the ram drive would make the circuit far more complex, also more gates for the extra logic. I'm planning to make a OS-ROM with an Cyclone IV connected to it , then the sky is the limit.... Quote Link to comment Share on other sites More sharing options...
ClausB Posted September 6, 2016 Share Posted September 6, 2016 The slot 2 board could have all the RAM, leaving slots 1 and 3 empty. Just wire A15 from the OS board as you did with S6. I did that in this mod: http://atariage.com/forums/topic/185500-using-the-atari-400-48k-board-in-the-800/?do=findComment&comment=2669222 2 Quote Link to comment Share on other sites More sharing options...
retrocanada76 Posted September 6, 2016 Author Share Posted September 6, 2016 The slot 2 board could have all the RAM, leaving slots 1 and 3 empty. Just wire A15 from the OS board as you did with S6. I did that in this mod: http://atariage.com/forums/topic/185500-using-the-atari-400-48k-board-in-the-800/?do=findComment&comment=2669222 What about the A14 without having S7, S0 and S1 ? How to you infer it ? Quote Link to comment Share on other sites More sharing options...
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