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LouisB

Rogue Atari 800XL Mod??

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Hello, I recently purchased an 800XL and when I plugged it in and turned it on it did this:

 

image.thumb.png.17040476f635e6df672f0746f76764b7.png

 

That was sort of odd to me.  Sometimes I could get it to ready if I held down option and hit reset.  I took it apart and found this:

 

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Does anyone have the foggiest what's going on here?  I have to admit, I'm an 8-bit hardware hacker newbie (i'm more the programmer type) so this is going to take awhile for me to figure out.

 

Thanks

 

 

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You've got a memory upgrade and an OS upgrade... looks like a switch is missing... check the ram and re attach the switch...

might be good to make sure nothing is jamming up the cartridge port either, sometimes you find the weirdest stuff in a cartridge slot.

Edited by _The Doctor__

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Ah, switch makes sense because there's a mysterious hole in the back next to the parallel bus.  Do you know what the other end of the switch would connect to?  Ground?

 

Thanks for the tip I'll check the cartridge port for random things.

 

I can tell you guys are knowledgeable, thanks for the quick responses.

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For some reason, I can only see your first picture, the rest are just a bunch of random characters. Apparently others can see more?

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I can't see all his stuff either, but I do recognize what I believe to to an old runner or XL fix OS with a switch to go between standard OS and Translator OS... it should come up as a Grey screen or memopad or standard Atari basic depending on installation and switching... in addition to that I see what I believe to be a memory upgrade...

Logical failure points being bad memory, bad switch wiring, or failing eprom...

so a clean and re-seat, followed by verification of installation and a test of ram, and eprom os seems the path to take.

Edited by _The Doctor__

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23 minutes ago, LouisB said:

Ah, OK.  I see it's something like this:

 

I don't see where the wire would connect now, it may have gone to a switch for a removed multi-OS mod, the machine currently has a 27128 containing only a single third-party OS.

Edited by BillC
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okay, looks like BillC can see the whole thing...

the new pictures show the hole for the switch was in the middle between the rf modulator and the monitor jack... and yes sadly something is missing...

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1 minute ago, _The Doctor__ said:

okay, looks like BillC can see the whole thing...

the new pictures show the hole for the switch was in the middle between the rf modulator and the monitor jack... and yes sadly something is missing...

Ok - yes that's bad news, but makes sense because I couldn't find any signs of a solder connection to the motherboard anywhere on the front or back.  I'll do some homework on memory upgrades, multi-OS mods and the like, thanks for helping me out on where to start.  A Trak disk drive came with it, but I haven't been able to fire it up.

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Most likely the other side of the switch would have gone to pin 27 of the EPROM for a 2 OS switcher..

Edited by JR>
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8 256Kx1 drams, like a RAMBO/Wiztronics/Newell 256K XL upgrade - just not one I recognize...

 

It's odd that if it had a 2xOS switcher in a former life, that they left the FIX XL OS chip, and not the original XL OS... I guess that might be fine if it's mostly used for playing games, such as the ones that have XL compatibility issues. :) Well, good news it's pretty easy to put a switcher/adapter back in.

 

I have an ICD Rambo 256K upgrade in one of my XL's, and your screen full of 0's seems vaguely familiar. because the larger DRAM's take longer to clear their contents after poweroff, you may find the system behaves erratically if you turn it back on too soon, and the OS only treats it as a warm start, not clearing the RAM. This is also commonly seen on 600XL's that are upgraded from 16 to 64KB RAM... Attribute it to higher quality memory with 'better' retention properties, but it is kind of annoying waiting the 10+ seconds to make sure the system starts clean...

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To clarify, I start up the computer, I have to reset a few times to get the "Ready" prompt, then when I type "LIST" that's when I get the screen full of 0's.  I waited awhile to see if it would stop, but seems to go on forever.

 

Thanks again for the info guys, I did some homework on Atari OS's and piggyback mods.  Next I have to dig into what a "Rambo" upgrade is and how it works.  It's not clear to me at the moment if I simply have a configuration issue with this unit, or something is faulty and needs testing / clean / re-seat and verification as The Doctor pointed out.  I'll keep working on it and report back.

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Turn on the computer holding the option key. You should go straight to the self-test. Choose Memory test, and see if you get any red blocks. Should be 48 total small blocks, and 2 large blocks for the OS ROM. It does not test the BASIC ROM.

 

You can also get to the self test by typing BYE from BASIC, but it will only test 40 blocks.

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48 minutes ago, Nezgar said:

Turn on the computer holding the option key. You should go straight to the self-test. Choose Memory test, and see if you get any red blocks. Should be 48 total small blocks, and 2 large blocks for the OS ROM. It does not test the BASIC ROM.

 

You can also get to the self test by typing BYE from BASIC, but it will only test 40 blocks.

Thanks Nezgar, holding the option key takes me to an unresponsive blue screen with a cursor. 

 

Sometimes I can get to basic by turning it on, then holding option and hitting reset.  When I type BYE I get a blue screen with a cursor.  I can type commands but they're not processed when I hit enter.

 

In the end I could not access the self-test screen by any means.

Edited by LouisB

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1 minute ago, LouisB said:

Thanks Nezgar, holding the option key takes me to an unresponsive blue screen with a cursor. 

 

Sometimes I can get to basic by turning it on, then holding option and hitting reset.  When I type BYE I get a blue screen with a cursor.  I can type commands but they're not processed when I hit enter.

 

In the end I could not access the self-test screen by any means.

Oh doy, of course. You have the XL-FIX ROM in there, which is not an XL OS, and won't have self test...

 

If you have another XL or XE you can swap an OS ROM from into this machine to test, that would help. If not, you can program a new 27c128 EPROM and plug it in to achieve the same. Then at least if the machine is still acting up, we can rule that out...

 

If you don't have the means to program an EPROM, I can do so and drop it in the mail for you, PM me.

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1 hour ago, Nezgar said:

Oh doy, of course. You have the XL-FIX ROM in there, which is not an XL OS, and won't have self test...

 

If you have another XL or XE you can swap an OS ROM from into this machine to test, that would help. If not, you can program a new 27c128 EPROM and plug it in to achieve the same. Then at least if the machine is still acting up, we can rule that out...

 

If you don't have the means to program an EPROM, I can do so and drop it in the mail for you, PM me.

Wow that's extremely generous of you!  I'll PM you right now

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You might also consider getting a set of 8 replacement RAM chips on their way to test swapping out.

 

here's an example listing for 41256 type DRAMs on ebay from a seller in Poland I've purchased from in the past:

https://www.ebay.com/itm/264063660256

 

And maybe I'll send you shoestrings memory tester on a second OS chip too if you are unable to boot software based testers...

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I recommend getting a Syscheck 2.2, it can diagnose many problems and also functions as external OS and external RamboXL compatible 512kB memory expansion.

 

One thing to be aware of is the new XL/XE compatible model doesn't support pass-thru for PBI devices, the version for the XL(also the XE) does have a PBI pass-thru but I have no experience of whether it works or not.

 

Edited by BillC
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13 minutes ago, BillC said:

I recommend getting a Syscheck 2.2, it can diagnose many problems and also functions as external OS and external RamboXL compatible 512kB memory expansion.

 

One thing to be aware of is the new XL/XE compatible model doesn't support pass-thru for PBI devices, the version for the XL(also the XE) does have a PBI pass-thru but I have no experience of whether it works or not.

 

Thanks for mentioning that, Sys-Check looks incredible (I watched this demo video) and it did come on my radar.  I'm going to hold off for now but i'm keeping that option in my back pocket.

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I think on the original xl fix mod it disabled internal basic chip and enable xl fix os if switching xl fix off internal basic would be back on... basic is suppose to be on cart when in 800 mode... I could be mixing old runner os up with xl fix os though.... just don't remember the specific details anymore...

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When I get the OS EPROMS from Nezgar I'll test everything out and report back.  I'm assuming this is a Rambo flavor bank switcher.  It took me awhile to get my head around the how, what and why of the memory upgrades, and this thread was extremely helpful and has it well in hand:

 

I would also add this article does a nice job of visualizing what's going on with memory bank selection / switching, Figure 1:

 

Figure  Atari Memory Configuration

 

As for how the extra memory is leveraged, at first I thought that somehow the OS would transparently make it available to the system, but now I see that each individual program, demo or DOS has to be smart enough to access the various bank switching methods in order to leverage it?

 

This thread covers some ground on that:

 

 

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Well, thanks to Nezgar sending me a few chips including this memory diagnostic utility, my 800XL is back in business!

 

2074610004_buyicnowrom.thumb.JPG.53908d7927243aac9dd379ff166e915c.JPG

 

MemTest.thumb.JPG.61be6049d54daf7ea6e2ef490a4ed022.JPG

 

And memory looks good.  

 

Now for my next project : 

 

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