Mrarkus Posted October 4, 2020 Share Posted October 4, 2020 I just acquired an 800XL with a Newell 256K RAM upgrade. It has two SPDT switches on top - one I figured out is a switch between Newell/Rambo mode for the upgrade. The other however I'm not sure what it is for: Center connected to Halt on Newell board One side connected to a cap by power connector via a resistor Other side connected to Antic Pin 9 (HALT signal) Any idea what this switch does? Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted October 4, 2020 Share Posted October 4, 2020 "Switch between newell/rambo mode" is a bit ambiguous - is that switching the bits used for bank selection? I believe Newell RAM upgrades had extra logic to prevent shadowing of the main 64K as 4 extended banks, whereas the simpler Claus Buchholz/ICD Rambo/Wiztronics 256K upgrades did not. Maybe a picture would help? Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted October 4, 2020 Share Posted October 4, 2020 The switch maybe a switch between 130XE style 128KB "ANTIC" and 256KB "non-ANTIC" banking modes according to this post about the Newell board: https://atariage.com/forums/topic/267985-newell-industries-256kb-xl-ram-issues/ Quote Link to comment Share on other sites More sharing options...
BobJones Posted October 4, 2020 Share Posted October 4, 2020 I seem to remember some ram upgraded with a switch where you could load a disk into a portion of ram , flip the switch, reset and boot the machine and use the ram upgrade as a super fast second drive. Works well with spell check software. But I could be wrong.Sent from my Pixel 4 XL using Tapatalk Quote Link to comment Share on other sites More sharing options...
Mrarkus Posted October 4, 2020 Author Share Posted October 4, 2020 (edited) 24 minutes ago, Nezgar said: "Switch between newell/rambo mode" is a bit ambiguous - is that switching the bits used for bank selection? I believe Newell RAM upgrades had extra logic to prevent shadowing of the main 64K as 4 extended banks, whereas the simpler Claus Buchholz/ICD Rambo/Wiztronics 256K upgrades did not. Maybe a picture would help? I found this article: https://www.atarimax.com/freenet/freenet_material/12.AtariLibrary/2.MiscellaneousTextFiles/showarticle.php?105 which matches what the first switch is and how it's connected. Here is a quote: This modification will make a Newell 256K Atari 800XL compatible with, the PD "130XE compatible" 800XL 256K project, as well as the RamboXL 256K kit for the 800/1200 XL's. In other words, Make Your Newell 256K 800XL compatible with Most of the other 800/1200 XL and 130XE Mods. The problem is a simple one. It seems the difference is in how the different modifications use Bit 5 off of the PIA chip. All you need to do is provide a way to invert this one signal in the Newell upgrade and it will operate like the Public Domain and RamboXL upgrades with all the excellent error checking the Newell 256K Provides. If you also provide a way to switch it back, it will act like the Newell again, Thus giving you the Best of Both Worlds. My concern is the second switch, which I can't find any info on. Edited October 4, 2020 by Mrarkus Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted October 4, 2020 Share Posted October 4, 2020 1 hour ago, Mrarkus said: My concern is the second switch, which I can't find any info on. Photo's inside and out would help us identify Quote Link to comment Share on other sites More sharing options...
Mrarkus Posted October 5, 2020 Author Share Posted October 5, 2020 OK, here we go, some pictures.... Quote Link to comment Share on other sites More sharing options...
Mrarkus Posted October 6, 2020 Author Share Posted October 6, 2020 I am going to give it one bump to see if anyone wants to take a stab at it... Quote Link to comment Share on other sites More sharing options...
TGB1718 Posted October 6, 2020 Share Posted October 6, 2020 Still not sure of it's function, but with the switch in one direction it just puts a pullup to +5V to the Newell HALT. In the other position it allows ANTIC to send the HALT signal to the Newell board, probably allowing ANTIC to refresh the RAM Quote Link to comment Share on other sites More sharing options...
ClausB Posted October 7, 2020 Share Posted October 7, 2020 HALT is used in the 130XE to determine whether ANTIC or SALLY is accessing RAM. So the switch defeats that separate ANTIC RAM access mode which the "PD" upgrade doesn't support (shame on the designer! ). 1 Quote Link to comment Share on other sites More sharing options...
+Nezgar Posted October 7, 2020 Share Posted October 7, 2020 So in a "Rambo/PD style" 320KB (256KB extended) computer, allowing separate antic banking reduces accessible extended RAM to 192KB. In a 256K machine, would this reduce accessible extended RAM since there was already only 192KB? If not, yeah - there's a grand total of what - 5 known titles that use separate antic banking? The effort to install the switch would then be of questionable value, but articles of the day made a big deal out of it... Quote Link to comment Share on other sites More sharing options...
Mrarkus Posted October 8, 2020 Author Share Posted October 8, 2020 Ok, that makes more sense now, thanks! Quote Link to comment Share on other sites More sharing options...
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