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RAM upgrade mod atari

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#76 Swami ONLINE  

Swami

    Dragonstomper

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Posted Tue Sep 26, 2017 10:53 PM

Antonia gives you memory, some switchable OS's, and an 816 CPU. The 816 and the RAM are great, But I couldn't live without all the features the U1M adds, Especially with Jon's BIOS.

 

Does anyone do installs of the U1MB or the new 4MB upgrades on a Taiwan 800xL or XEGS, or sell 800XLs already upgraded? I don't think my soldering experience is up to it.



#77 martinez OFFLINE  

martinez

    Combat Commando

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Posted Wed Sep 27, 2017 12:50 AM

As far as U1MB is concerned, you may send mobo to Lotharek and get it back upgraded. He charges additional fee for the job.



#78 mutterminder OFFLINE  

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Posted Sun Oct 8, 2017 2:27 PM

I'm planning to install the U1MB in my 600xl and in checking my 64K memory upgrade, I found that it does not match any of the common upgrades.  I put it in at least 15 years ago, maybe more and I don't remember where I got it. The 64K chips have their markings sanded off.  I have wires soldered to the lifted legs of U5-3 and U6-9, but they go to U2-4, and 5.  Also U18 pins 8, 9, and 10 are lifted.  There are just the two wires.  Does anybody know anything about this upgrade?



#79 mutterminder OFFLINE  

mutterminder

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Posted Sun Oct 8, 2017 6:55 PM

To add to the above, in case it isn't obvious.  Because the wires are soldered to the MMU, I'm not sure that this particular memory upgrade is even compatible with the U1MB.



#80 tf_hh OFFLINE  

tf_hh

    Moonsweeper

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Posted Mon Oct 9, 2017 6:23 AM

I'm planning to install the U1MB in my 600xl and in checking my 64K memory upgrade, I found that it does not match any of the common upgrades.  I put it in at least 15 years ago, maybe more and I don't remember where I got it. The 64K chips have their markings sanded off.  I have wires soldered to the lifted legs of U5-3 and U6-9, but they go to U2-4, and 5.  Also U18 pins 8, 9, and 10 are lifted.  There are just the two wires.  Does anybody know anything about this upgrade?

 

Sounds ok. The lifted pin at U6 should be 10, not 9. The both cables connect the missing address lines needed for selecting something over 16K - A14 and A15. You can take these both from the MMU like in your solution, the CPU, the 74LS375 (U15) or some solder joints.

 

U18 (74LS32) is only needed to limit the CAS signal to the lower 16K. When pins 8, 9 and 10 are bended up, there must be a connection between pin 8 and 10 somewhere, maybe from the bottom of the PCB or chip itself.

 

I see no problem to install an U1MB. Remove the both wires connected to the MMU and solder them to an other place, for example:

 

A14 = pin 9 of U15 (74LS375)

A15 = pin 15 of U15 (74LS375)



#81 mutterminder OFFLINE  

mutterminder

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Posted Mon Oct 9, 2017 6:38 AM

 

Sounds ok. The lifted pin at U6 should be 10, not 9. The both cables connect the missing address lines needed for selecting something over 16K - A14 and A15. You can take these both from the MMU like in your solution, the CPU, the 74LS375 (U15) or some solder joints.

 

U18 (74LS32) is only needed to limit the CAS signal to the lower 16K. When pins 8, 9 and 10 are bended up, there must be a connection between pin 8 and 10 somewhere, maybe from the bottom of the PCB or chip itself.

 

I see no problem to install an U1MB. Remove the both wires connected to the MMU and solder them to an other place, for example:

 

A14 = pin 9 of U15 (74LS375)

A15 = pin 15 of U15 (74LS375)

Thanks for the feedback I was just going through the schematic myself to see if I could figure out what was going on.  The situation at U18 concerned me.  You are probably right, there may be another jumper somewhere on the board that I don't see,  like I said, I installed this upgrade a long time ago, so I don't remember anything about it.  I Think I'll follow your suggestion about finding A14 and 15 somewhere else.



#82 mutterminder OFFLINE  

mutterminder

    Star Raider

  • 72 posts

Posted Mon Oct 9, 2017 6:50 PM

Sure enough there was a jumper on the bottom of the card between U18-8 and 10. While this does preserve the the CAS going where it needs to go, I decided to just lift pin 9 of U18 and short it to ground on PIN 7.  (Oh and it was U6-10 and not 9). Now to to install the U1MB. :)



#83 tep392 OFFLINE  

tep392

    River Patroller

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Posted Sat Oct 14, 2017 2:21 PM

So, no current memory upgrades available for an 800 past 64K?

An Axlon type board has been design but you would have to order the parts and build it.  I've built a few.

http://atariage.com/...oard/?hl= axlon



#84 Stephen OFFLINE  

Stephen

    Quadrunner

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Posted Sat Oct 14, 2017 5:13 PM

An Axlon type board has been design but you would have to order the parts and build it.  I've built a few.

http://atariage.com/...oard/?hl= axlon

Very cool video BTW.



#85 tep392 OFFLINE  

tep392

    River Patroller

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  • Location:Peoria, IL

Posted Sat Oct 14, 2017 6:26 PM

Very cool video BTW.

Thank you!  I really love that 800. :)



#86 Stephen OFFLINE  

Stephen

    Quadrunner

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Posted Sat Oct 14, 2017 9:13 PM

Thank you!  I really love that 800. :)

If I get this Bit3 working, my Incognito will be the always hooked up machine in my basement setup.







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