A little bit of 8 Bit: 65XE upgrade to 128k RAM

Any 8bit repairs, images, cool things, upgrades etc.
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rubber_jonnie
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by rubber_jonnie » Thu Mar 22, 2018 9:25 am

walter_j64bit wrote:
Thu Mar 22, 2018 2:20 am
A 65XE to 128k nice work! I would love to see 65XE to 256K. 8-)
Took me an age to get the bits and details, so I thought it'd be good to document, and it's brought some other good info too.
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

ChaoticBiker
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by ChaoticBiker » Mon Jun 08, 2020 2:37 pm

Hello,
I'm new to this forum and decided to dig up this old topic.
I am trying to follow Jurgen's upgrade for 320kb. Doing this to an 800XE, board C070067 rev b

I have followed the instructions closely and have the GAL chip programmed as per file (not by me). I am also using the 100nF ceramic capacitors next to the chips.
I have a couple of questions, as my Atari is not powering up with the upgrade, it seems like it's trying giving a meshy looking red screen.

1. I am drawing the +5v off C308 next to to SIA port, where I've soldered the 3.3kOhm resistor and a wire to ling to PIN16 of PIA (U23) and then another wire off that very pin to GAL pin 7.
Do I need to cut anything out from PIN16 in the PIA? e.g. do I need to disconnect it from the motherboard? It doesn't look like there are any traces going out from it.

2. for PIN 13 of the GAL to PIN 6 of the MMU, I have put a wire just between the 3 resistors tight under the MMU, there's a connection there that goes to PIN 6 of the MMU. I have then cut the trace so it doesn't go to the PIA. Is this about right?

3. What else can I try to diagnose what might be the problem?

Thank you in advance for all your help with this

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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by rubber_jonnie » Mon Jun 08, 2020 2:46 pm

ChaoticBiker wrote:
Mon Jun 08, 2020 2:37 pm
Hello,
I'm new to this forum and decided to dig up this old topic.
I am trying to follow Jurgen's upgrade for 320kb.

I have followed the instructions closely and have the GAL chip programmed as per file (not by me). I am also using the 100nF ceramic capacitors next to the chips.
I have a couple of questions, as my Atari is not powering up with the upgrade, it seems like it's trying giving a meshy looking red screen.

1. I am drawing the +5v off C308 next to to SIA port, where I've soldered the 3.3kOhm resistor and a wire to ling to PIN16 of PIA (U23) and then another wire off that very pin to GAL pin 7.
Do I need to cut anything out from PIN16 in the PIA? e.g. do I need to disconnect it from the motherboard? It doesn't look like there are any traces going out from it.

2. for PIN 13 of the GAL to PIN 6 of the MMU, I have put a wire just between the 3 resistors tight under the MMU, there's a connection there that goes to PIN 6 of the MMU. I have then cut the trace so it doesn't go to the PIA. Is this about right?

3. What else can I try to diagnose what might be the problem?

Thank you in advance for all your help with this
I've not done this specific upgrade myself, but FYI you can tag people by typing @ then begin to type in their forum name and pick from the list, and they will get a notification.

@tfhh and @guus.assmann are you able to offer any help with this?

Good luck.
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

guus.assmann
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by guus.assmann » Mon Jun 08, 2020 6:41 pm

Hello,

Did you leave pin 7, 8, 9, 12 and 13 from the GAL out of the board and bend them up?
They shouldn't make any connection to the MB.
The redish screen usually means a Ram fault or the CPU not running.

To test the standard part, remove R111 at the side that's not connected to pin 15 of the Ram and connest that to +5V.
Now the extra Ram is disabled becaue CAS is permanenly inactive of the extension bank.
If the computer boots, you could remove R110 on one side that's not connected to pin 15 and connect that to +5v.
remove the connection of +5V to R111 and connect that to where R110 was.
You now hate the extra ram as main ram.
If that works as well, the ram is ok and the selection is somewhere at fault.

I've attached the part of the schematics that you need to find the fault.
130xe_04b.gif
130xe_04b.gif (23.92 KiB) Viewed 1507 times
Please note that the schematics are from the original 130XE and not for the enhancement that in previous posts.
BR/
Guus

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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by rubber_jonnie » Mon Jun 08, 2020 9:52 pm

Thanks @guus.assmann
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

ChaoticBiker
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by ChaoticBiker » Tue Jun 09, 2020 8:53 am

Thanks @guus.assmann , that's really helpful.
The pins on my GAL, 7,8,9 and 12 13 are all bent up, do not touch the socket and have wires soldered to them. Pin 7 on the GAL goes to Pin 16 (orange/white wire) of the PIa (6250) and another orange/white wire from PIN 16 goes to +5v through a 3.3kOhm resistor. GAL pin 8 goes o Pin 17 on the PIA (blue wire ). Pin 9 (brown wire) is grounded exactly same way as in Jurgen's original guide as I'm not using a switch.
GAL Pin 12 goes through brown/white wire and a 33Ohm resistor to all pin 1's on all the DRAM chips, as per "Method 1" by Jurgen.
GAL Pin 13 goes through brown wire to pin 6 of the MMU C061618-20 through a solder located physically below R15 on the board, and a trace is cut so it no longer connects to PIA.

I am struggling to locate the R111. I understand it's one of those right under U34 (the GAL chip)? Which pin should I trace as it's not that clear from the schematic?
IMG_3835.JPG
IMG_3835.JPG (400.95 KiB) Viewed 1482 times

ChaoticBiker
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by ChaoticBiker » Tue Jun 09, 2020 2:17 pm

ok so I locater R111, desoldered one side (the side that's not going to the RAM) and connected +5v to it.
Doesn't look like it changed anything.
None of the chips heat up noticeably, though I've only got my fingers to check so might be missing something.

Wee update - checked the RAM chips separately - they do work
Checked the inbuilt rams by piggybacking known good ram on top

All to the same (=no) effect.

I'm leaning towards the issue being somewhere either around PIA or GAL chips. I have another GAL chip programmed for 128k so might try that one too.

ChaoticBiker
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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by ChaoticBiker » Tue Jun 09, 2020 4:26 pm

FIXED (almost!)
well it turns out it was all down to a single bad / cold solder point....

However now I have another issue - my Atari won't reset... loads up fine, sio2sd menu loads up as expected, keyboard is working etc.
no response to Reset button. I am almost certain this has to do with how I routed the +5v....

So my new question - where is best place to source +5v off so it only gets it when the Atari is on? And preferably close to PIA chip.

guus.assmann
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A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by guus.assmann » Tue Jun 09, 2020 7:04 pm

Good that you found the problem. :D
Soldering jobs are not always as easy as they look.

This may not be a reset problem but a totally different one.
To check that theory, take a game cartridge.
Switch off, plug the cartridge and switch on. The cartridge should run.
Now switch off, pull the cartridge and switch on again.
The computer should boot as usual.

If this works, the Ram´s are the problem.
Newer Rams don´t loose the data fast enough.
Waiting for about 1 minute or more should also help.
I have more OS-es in my computer and switch between those.
This clears some of the ram-location that the OS looks for to detect a cold start.

BR-
Guus

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Re: A little bit of 8 Bit: 65XE upgrade to 128k RAM

Post by rubber_jonnie » Tue Jun 09, 2020 7:26 pm

ChaoticBiker wrote:
Tue Jun 09, 2020 4:26 pm
FIXED (almost!)
well it turns out it was all down to a single bad / cold solder point....
Had this problem on my Mega ST 4, one bad connection on the ground to one of the ROMs and all sorts of erratic behaviour. Glad you've moved forward.
Collector of old Atari things:
800XL + Ultimate 1MB, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k +APE Warp) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg), 1040STF long button floppy, 2x 1040 STFMs + Gotek, 2x 4160STE with 32Mhz booster, ROM switcher, Mega ST1, Mega ST4, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

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