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Newell 256K and Ultimate 1MB Upgrades Together?


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Hi, this is my first post here.  I recently pulled my 800XL from storage and got it going again.  I have been reading this forum for weeks and can't find the answer I am looking for, so please help.  This 800XL has the Newell 256K upgrade installed along with a switchable Omniview bios chip.  I see there is a pretty cool upgrade out there (Ultimate 1MB) which I am interested in installing, but I would prefer not to remove the Newell upgrade and just add the Ultimate upgrade.  Can I do this?  Can they coexist peacefully without any memory conflict issues?  To be clear, I would not activate the Newell memory with software, just want to leave it installed doing "nothing" and instead use the Ultimate 1MB for additional memory.  I see that there are two possible switch installations for the Newell upgrade:  1)Newell says I can install a switch which provides PIA chip pin 15 with two different signal sources to make it look like "other" memory and 2) 3rd party mod says I can put a switch on the Halt line to determine whether Antic will follow either main or banked memory.  Will installing either one of these switches help?  Perhaps someone can explain to me exactly what they do since it is beyond me.  I am good at soldering so I could install either of these or both of these switches or even a different one that could "deactivate" the Newell memory.  Thanks!

Edited by jgrass
Also, as a first poster, I see I posted in wrong category. Sorry, can someone move to correct forum location?
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Basically the extended memory as used in the Atari scheme is to send the active memory bank the /CAS signal and that allows each memory chip in that bank array to decode for it's desired address for read or write on the data buss at the appropriate time. Without the /CAS signal, the memory chips then enter what's called /RAS only refresh mode where the data in/out buffers are tri-stated (unaccessable/disconnected from data buss) while address is decoded internally but is only used to refresh an entire row of memory cells. Each memory chip has the smarts to know which it should be doing by the /CAS signal going low. The / forward slash used on /CAS as I type it is supposed to be a bar across the top of it to notify those interested that it is a negative active logic state. So keep the /CAS line high all the time and that memory bank of chips is asleep and undergoing memory refresh on it's own internal counters. Turning on a bank of memory chips then requires the one and only /CAS signal to reach that set of particular memory chips.


So how to do it is where I can't help since I don't have knowledge of just how 1UMB works in the details.


1) Newell misspoke about the switch and was referring to another issue while using compatible talk to avoid the actual question about Antic access. It's not a thing with a Newell upgrade and never will be without the 2nd MMU of the 130XE wired into the circuit so that actual emulation of that talent occurs. 2) Same for 2nd switch advice then too, neither writer understands the complexity of Antic access nor how to bring it to a memory upgrade properly. 1UMB has it and it works fine, Newell will never have it and never did.


And what you want is something else entirely. There is nothing great or wonderful about the Newell, I have a one (four) meg FYI, I can not shut mine off with or without software. So I would have to install a switch to keep /CAS away from the input of the Newell and to also then shunt it to the 1UMB instead for it's use alone. Something like that might work, but I see no reason to keep the Newell since the 1UMB will give you one if you select for it. The off /CAS input then should be held high with a 4.7K resistor to insure that two memory banks are not trying to access the data buss at the same time.


So PIA pin 15 is bit 5 of PORTB 0xD301. In an Antic access upgrade, is it used to determine if Antic has access to the ram window at 0x4000 - 0x7FFF or the CPU has that access or neither/both do. It can not then be used as a banking byte to select the number of which bank of memory is in that window in Antic access upgrades. This requires a separate MMU in the 130XE since the /CAS shifting must occur during the /HALT event if it is to occur. Antic can then use the extended memory window while regular CPU Base memory for the window is refreshing. And vica versa as the case may be.


PIA pin 14 is bit 4 of PORTB 0xD301. It selects the CPU access to the extended memory bank for the ram window at 0x4000 - 0x7FFF, just like bit 5 does for Antic in Antic access upgrades. Bit 4 (and 5 in Antic access upgrades) are low active signal(s) so both high mean that the window data is coming from Base memory and extended memory is in /RAS only refresh mode.


Clear as mud even for me, I hold no opinion that Antic access is even desirable, but without it some Demos won't display/work right. You can't make a Newell into one of those by any simple switch or solder bridge. For Antic access you need both /CAS and /HALT signals decoded by logic chips before they happen so to speak in order before the switch of the proper window at 0x4000 - 0x7FFF occurs properly. This is the rub, apparently /HALT occurs before /CAS and this then requires the effect of a latch to hold its value such that straight glue logic fails to provide a working solution. We need a properly programmed GAL or PAL which is what Atari used in the 2nd MMU of the 130XE to pull off the magic of Antic access. 1UMB has the GAL which is also selecting an array of Antic access and other memory types/sizes including Newell.


ATB, stay safe out there people.

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With another bank of memory installed in the same access space, program data could stay in normal banks and Antic could have it's data in that extra memory, running it almost independent of anything else... but that's another story and upgrade... let's just say more was planned for freddie/mmu than what ended up being delivered.

Separate ANTIC access can still be leveraged in the current form to do some nice things. The X Comm wedge uses it as well, some demos, the community really hasn't explored or used this nearly as well as it should have.


The newell and other upgrades can use what is called ANTIC following... depending on use, you might see some flicker-but you will at least get to see the VIDEO as opposed to none at all or errrors...


Bottom line, just use the U1M... it does it all.

Edited by _The Doctor__
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