1. Not old. Vintage. :)

XE Games System - RAM upgrade

Discussion in 'SIG: Atari 8-Bit Hardware' started by kokkiklhs, Aug 15, 2020.

  1. by kokkiklhs
    kokkiklhs

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    Hiya, atari-gurus!!
    I recently acquired a long-desired XEGS and I'd like to upgrade it at least to 128k, with some DIY procedure (not the manufactured RAM upgrade kits that are being sold through the web)... I googled a bit but found almost no information about such a job on this specific machine, as it has a different PCB compared to the regular XE's (and XL's, of course...)
    Only located a german webpage (don't even remember where), but the directions were poor and didn't understand much...

    So the question is, has anyone in here upgraded the RAM of an XEGS? Could some fellow make a step-by-step guide, with some explanatory info and photos? I suppose that for anyone who knows, it would be rather simple, following the regular 128k upgrade guides (or even the 512k SRAM+GAL upgrade by Hiassoft) and adapting the guide on the special XEGS PCB layout...

    I believe that a 128k (or more) upgraded XEGS with keyboard would be the most beautiful last generation 8-bit Atari machine that a collector could have, very stylish and elegant little piece of hardware...

    TIA for any assistance!!
     
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  2. by Vyper68
    Vyper68

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    Jürgen’s 512KB RAM board fits an XEGS and of course there is the Ultimate 1MB upgrade as well. They both need some level of desoldering skill and the XE PCB’s are easy to damage so bear that in mind.
     
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  3. by Graham
    Graham

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    Hi
    Yep XEGS boards as bad as the other XE series boards for lifting tracks.
    One pretty simple update upgrade is upto 128K
    Needs two additional 4x64K chips (there the one very bottom left.) An EMMU from a 130 XE a 33Ohm resistor and a bit of care. wiring it all together, there maybe be a way of using a 74LS95 chip and one other instead of the EMMU
    The additional RAM chips are piggy backed on the originals, Bar one leg, the two legs one from each chip connected to each other with a fly lead. This will attach to the EMMU, also need multiple conections from PIA chip for Bank selection, and a pair of wires from Freddie FA14 & FA15, there are others.
    I can dig out the upgrades and post on here for you. other than that Third party options I'm afraid. best solution maybe to put one that sit under the CPU or Antic not sure which, and instead of de soldering, clip the original chip out and buy a new one to pop in, only leaves indiviual legs to desolder.
    Strange you mention this as I've been building an XEGS board from scrach, and only started on it yesterday properly.
    By the way. I'd be happy to help you if you wanted to send it to me, and I know JazzFlashCat on AA would also do the work.
    Happy to discuss.
    Before I write anything up to post better to discuss what you really want to do as the U1MB is a great board, or you may want something from Jurgen known as (tfhh on AA) as mention above.
     

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    Last edited: Aug 16, 2020
  4. by kokkiklhs
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    @Vyper68 and @Graham thank you both, fellows, for your answers!
    I am looking for exactly what Graham describes as a complete DIY option! 128k are more than enough for me! Of course the ready-to-go solutions are more sophisticated and are likely to cover all my future needs (thanks also for Jurgen's list, Graham, I especially liked the 512k expansion and the stereo POKEY board) and the prices are also very reasonable, but I'm the soldering iron-addict guy, so I'd definitely go for the higher fun-factor choice! ;)

    So, if Graham could find and post here the 128k mod for the XEGS, it would be fine for me! I am particularly interested in using the 74LSxx circuitry instead of the EMMU, as the latter is rather rare and expensive, if found (in fact it would cost more than buying a ready made 512k expansion from Jurgen, hahaha)... :D

    We are not in a hurry, whenever some spare time is found, it would be great for the 128k mod to be posted here, I'm sure that other XEGS owners will be interested, as well! :)

    Last but not least, thank you Graham for your kind offer, but what keeps my interest for these machines alive is mostly hardware modding and fiddling, so I'd really prefer to do this with my own hands!

    Cheers, mates and thank you again!!
    :cool:
     
  5. by Graham
    Graham

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    HeHe well we share a similar passion re playing with hardware.
    I'm not sure I have a post to share, which is why I asked, I think I'll have to write it for you.
    I know on the 130XE you can use a 74LS95 I think they are rare but not so bad as the EMMU.
    So it would be a combination of the 130XE upgrade, along with using a 'MOD' to utilise LS' chips.
    Meanwhile take a look at this. https://atari-owner.com/club/blogs/xegs-new-circuit-board-build-16-08-2020.9/
     
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  6. by Vyper68
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  7. by Graham
    Graham

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    Thanks Richie
     
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  8. by kokkiklhs
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    Thanks!! So, I see there's a GAL also required...
    Is it the exactly same GAL that Hiassoft used with thw 512k SRAM upgrade?
     
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  9. by Vyper68
    Vyper68

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    Well looking at Jurgen’s current PCB he is using two 22v10 gals so I think so as the article does reference 22v10’s as well as some logic chips and Jurgen’s expansion has a SMD logic chip as well.
    There looks to be a 74ls95 & Gal16v8 for 128K or if you want bankswitching for 256K you go down the Gal6002, Gal22v10 or 20v8 the latter two needing a 74ls04 as well.
    If it were me I probably wouldn’t get into creating something that can be picked up for €25 and works out of the box.
    That said I know you want to get your hands dirty :):):)
    Just remember to document your progress here!
     
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  10. by kokkiklhs
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    Hmmmm, very tempting idea, as a GAL needs progamming and I don't have a suitable programmer here... I'll think about and and decide through time, right now I am between the two solutions... :D
     
  11. by Graham
    Graham

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    Hi kokkiklhs

    Unfortunately not.
    The eMMU is a smaller chip than used in the 512K upgrade, and does a slightly different job
    The replacement for the eMMU uses a GAL16v8 plus the 74LS95 that was an empty socket on the 130XE board.
    The XEGS is very similar but used 4 bit wide Memory chips, 2x 4x64k rather than 8x 1x64k
    the additional chips only have one leg wired differently to the originals.(some later 65/130XE's used either 2 or 4 chips as well)
    On the 130XE Freddie works with the eMMU and allows refresh cycles to keep the additional memory working.
    So in effect you'll need to do the same, as eMMU is getting expensive the GAL16V8 a 20 pin device can be used with the 74LS95. This is likely the easiest route to follow bar having an original eMMU which is a custom made 16 pin device.

    eMMU_NOTES.png


    The 512K SRAM upgrade essentially does not require any refresh cycles, so the GAL chip used on this upgrade work slightly different.
    Firstly the chip is a 22V10 a 24pin device, exactly the same as the 'MMU' but with different programming. Update sorry wrong its 20 pins!
    This allows several types of memory upgrade 'type' to be emulated, using additional PORTB pins to switch in additional banks of memory. A standard 130XE has 4 banks (8K), and both the 6502, and the Antic processor can control the bank switching independently, so some memory upgrades don't allow for this and use this 'bit' to switch in additional Banks of memory, the internal Basic also has a control line from PORTB and again some memory upgrades use this 'bit' for themselves leaving the only option to use cartridge based Basic rather than internal.

    Since I don't mark up my supply of logic chips a 7432 rather than 74LS95 shown below as some idea of whats to be added.
    2020-08-21 12.38.39.jpg 2020-08-21 12.38.54.jpg 2020-08-21 13.03.33.jpg 2020-08-21 13.05.25.jpg

    I'm a little busy with building my XEGS and re drawing the schematics (Hopefully corrected)
    But I'll sort out the circuit for you.
    Hope this is of some value.
     
    Last edited: Aug 21, 2020
  12. by kokkiklhs
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    Gee, thanks Graham for the prompt reply and the detailed info!
    You both guys are great!
    :)
     
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  13. by Graham
    Graham

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    I hadn't checked your online, do you have the equipment to program a GAL ? I could possibly supply an eMMU as I have One spare. (I'd have to check it works o.k)
    Unfortunatly have to go fo about 30 mins.
     
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  14. by Graham
    Graham

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    Something strange going on as I'd missed Richies post above and the reply completly until I logged back on .. sorry Guys
     
  15. by Graham
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    I must admit it's nice doing your own thing, but the 512K upgrade is approx 23 Euro + post.
    see attached
     

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  16. by M.D.Baker
    M.D.Baker

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    I like to do my own thing too, but when it came to ram upgrades, I always went with a kit or now external device. The first ever DIY ram upgrade I was going to do was the 800, hacking it's ram boards using ClausB's old schematics, but in the middle of it the Incognito returned, so once again I went with a kit and got it instead. These days with all the internal and external upgrades other than ram seem to come with 512k or 1MB extended ram as a bonus, so it almost doesn't make much sense to build your own or do a ram-only kit, when these other upgrades deliver so much value for the money with multiple upgrades on board. 800 Incognito: 1MB extended ram, 4 OS slots, SDX on board, 64K flash ram, CF storage and loading device. Ultimate 1MB (all XL/XE machines): 1MB extended ram, 4 OS slots, SDX on board, Side 2/3 CF cartridge storage and loading expansion available for it. Syscheck 2.0 (All XL/XE with PBI/ECI): 512K extended ram, 4 OS slots (1 is diagnostic OS). Just three examples, there are more PBI/ECI upgrades that include extended ram among other things too_Of course in your case with the XEGS and no ECI, @kokkiklhs , the U1MB is the only multi-upgrade-in-one kits that will work.

    Of course I still make use of what I have on-hand, even if it's just ram or OS upgrades alone. I just did a Dual-Pokey stereo, piggy-back style DIY upgrade for my 800 while installing the incognito, because all the stereo kit boards won't fit in an 800, but then went and purchased the Pokeymax Quad plus Covox because it will fit, so the piggy-back DIY goes into a 1200XL now. I'll still be making my own DIY internal amplifier and audio/video output board for the Pokey upgrade, and my own dual-PIA upgrade that will also include a DIY board for extra controller ports and a second SIO port for my 800 as well. And eventually a real PBI PCB-edge connector out the back too! The point being there are plenty of opportunities to still do cheap DIY upgrades and mods for fun and satisfaction, even if you go with multi-upgrade-in-one kit boards too.
     
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  17. by Graham
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    Hi Matt , kokkiklhs
    I have to agree that the U1MB is a nice solution for the XEGS, or indeed any of the XL & XE line, certainly with the limitations of having no PBI/ECI. The incognito goes without saying for the 800 (I'm guessing 400 as well)
    One nice thing the XEGS has going for it is the space within the casing, with no keyboard having to be accommodated, and the resulting 'slope' there is a great deal of room to add extra's (although the angled ports & Cart port take up additional space that can't easily be used)
    I've been working on my XEGS this morning, only adding the components to give me a system that initially boot to the ready prompt.
    Sophia2 hasn't made an appearance as yet which is a shame; I was hoping to do away with the PAL colour clock, and the colour adjustment circuit.(built into Sophia2) I've found even more mistakes with the drawings as well so I'm making notes as I go along. I will be using a DVI Sophia (the original) so I won’t be adding any of video components at all, not sure at the moment weather I need to load the GITA output lines, usually 1KOhm to +5V.

    I've also started the outline design of a replacement motherboard, so far the outline, the original ports and Cartridge port. I’ve added the U1MB in a similar way to Mytek inverted and sat in place, Not much else, the idea will be to produce something similar to the 1088XEL/XLD's that Mytek put together; but with my own extensions added; my XEGS Blog shows a few ideas on this, some will be realised as an add-on daughter card, early days yet, and completely self serving, such things as a CF interface, MIDI, DVI etc.

    I'm looking forward to what you decide on for your XEGS, I'm also going to rebuild the original SRAM under O.S Rom boards, I've found some other designs supposedly designed by John May, (Computer House UK) however I know he had no idea in regard electronics, as he never understood what I was doing!
    I'll have to update the addressing to these at some point but it's to allow me to learn, or re learn assembler on the 6502.

    I hope you keep us all updated, and share your upgrade whatever way you go !
     
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  18. by kokkiklhs
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    Well, the latest news are not at all good...
    I finally found some time to fire up the XEGS, so far I had only unboxed it, to check cosmetic condition...
    Meanwhile, I have decided to order (and did order) a ready made 512k SRAM expansion from Juergen, it is the easiest and by far most economic solution. As for my soldering appetite, I have many other projects open, so I don't mind much...
    Back to my testing: On power on, guess what? BLACK SCREEN of death! Such a frustrating experience, I bought it as working item long ago, no I no longer have the right to return it or claim my money back... Silly me, I just let the time pass, now I had this situation in return... Well, never again, I should be more careful...
    Anyway, I gave the machine for free to a friend of mine, who is a real atari freak and has good repairing skills. I didn't want it hanging around my place anymore, I was just so disappointed... I hope he fixes it and keeps it, but meanwhile he tells me that he needs a good schematic to help him... He has found on the web a XEGS schematic which seems to have a lot of mistakes. So far he has found many short-circuits around the board (which is in perfect shape), seems that the previous owner must have pulled/inserted a cart while the machine was operating, or something...
    Is there anybody in here who has a GOOD, decent schematic for the XEGS? Please help, I'd like to see it coming back to life in my friend's hands...
    As for the SRAM expansion that I've ordered, this will (sometime) fit into my 800XE..
    :)
     
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  19. by M.D.Baker
    M.D.Baker

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    I did this with a Arduino Uno I purchased, so I know what you mean...but guess what? I did it again with an Elegoo Uno too! I still haven't bothered to check it out, so if it's not working that'll be twice for me...actually more times than that I buy hardware and it sits for months, but the Arduino Uno was the first that wouldn't work for me. If I buy a full machine, I do test them right away!
     
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  20. by Graham
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    Oh Dear
    I'm sorry to here of your woe's and I hope your friend is careful with a soldering iron, from experiance I can say the traces often lift, If you know for definate which chip is dead its far better to clip each leg, and remove the IC itself, then carefully tackle each IC pin one at a time. Thats not to say that they can't be extracted in one go but a proper desoldering gun, and a decent hotair soldering gun/pencil will make all the difference.

    Yes There are many mistakes in Jerzy Sobola's XEGS diagrams.
    I'm currently redoing them in KiCAD from a revision A board.
    They will include the PAL colour clock (not available from Jerzy), and the colour adjment circuit with corrected component numbers among many other things, such as there are four power rails with individual filtering and not the three show in his diagrams.
    I'm about a week away from release as PDF's or soon after , they will appear in the XEGS build BLOG thats on here (by myself) there are some pictures there at the moment but they may still have some mistakes until final release as attached PDF's
    There is a resource re black screen of death somewhere on here AOC as well; originally on another Atari board and reposted here.
    This maybe the quickest way of sorting the problem.
    New diagrams second.
    Lets hope he get it working so he can sell it to me :)
     
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  21. by kokkiklhs
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    Thank you very much for the help, I'll look for the BSOD troubleshooting guide...
    Meanwhile my friend already knows about the bad quality of the PCB (I had similar experience once with a Sinclair QL, an Atari STE, and a A590 HD for the Amiga, very nasty PCBs all 3 of them) and he has ordered a new Sally, it's definitely fried, as the oscilloscope says...
     
  22. by Graham
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    Yes Sally is a common issue unfortunately, hopefully it's not fried just failed, as otherwise it would indicate lots of other blown chips. The ROM is another favourite failure point as masked ROM's in many computers have started to fail

    Freddie is very susceptible to static as it uses CMOS technology, all the other Atari LSI chips are NMOS and tend to be fairly resilient, even to way to much voltage etc.

    Sounds like your friend has the correct equipment to test and repair with as well, so hope he gets it working. As I said, if you / he is interested in selling I may be interested in buying it, depends a little on what you have and the value you place on it.
     
  23. by kokkiklhs
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    I think he'll manage to fix it, he has already replaced the ROM and one bad RAM chip and also working on replacing Freddie... Hopefully he has some atari-junk around, for donor purposes...
     

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