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aquaz

130XE behaves in a weird way - memory problem?

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I've just got Atari 130XE - it looks very well on the outside and on the inside, but there are some major problems.

Barely any application or game loads - I'm using SIO2USB with several disk drive emulators (RespeQt, AspeQt, SIO2BSD, atarisio) on variety of operating systems (Windows 7, 10, Linux, emulated XP) and some ATR/XEX files load, some don't.

Most of them froze after reading several sectors, some loaded successfully but were crashing and freezing when trying to access memory.

I have some zins that make use of extended 64k on 130XE and those were crashing as well.

Built-in memory test passes with all green, but some of diagnostic applications I've managed to start are showing really weird results - depending on application I use and how many restarts I've made... 

Sometimes they're reporting 96k, sometimes 64k, one application refused to load because base 48k weren't available. One memory test is showing a lot of errors.

https://www.youtube.com/watch?v=C4nZPRWjRBc

 

Not sure what to look for - should I start trying to replace memory chips, maybe it's some issue with MMU?

 

icet.jpg

memtest.jpg

sysinfonew.jpg

sysinfoold.jpg

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you may have an issue with the extended 64k bank.

you can try the piggyback method or there is another mod you can do to make the 2 banks 'swap places' to diagnose this - it involves switching 2x resistors so that they cross over instead of side by side. the info will be in the forum here. then the second bank will be the primary one which is tested by the inbuilt tester.

try to test RAM with software called XRAM or SHORTEST as they are compatible with the various extended memory banking schemes.

good luck!

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here is a link:

 

the piggyback method is quicker and less involved but you need sapre RAM chips to do it.

the user in the above link, tf_hh makes a device called "sys-check II" which diagnoses memory faults. it also has a 512kb upgrade and ROM 'slots'. a v.useful device 🙂

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The 130XE is notorious for bad Memory, using the "MT" (micron) memory chips as shown in this picture. It looks like your base 64K may be OK, and Ice-T reporting an issue with 48K maybe because you didn't disable BASIC (holding option on poweron), or simply because it needs use of the extended 64K, which is not working well.  The base 64K is the far left column of chips on the motherboard. The "Extended" 64K is the next column to the right. Your video of the extended memory test failing, and Sys-Info only reporting 32K extended memory suggests one or more of those extended RAM chips are bad.

 

You'll have to figure out which chips in the 2nd row are bad, or replace them all, which also involves desoldering and replacing sockets for all 8 chips. I have not had much success with the "piggyback method" myself... With a Sys-Check from tf_hh as previously linked, it will test the MAIN 64K and (usually) indicate which specific chip is bad. it doesn't test the extended 64K, but as mentioned by @xrbrevin, you can swap the legs of one side of R110 and R111 as pictured below, and the extended 64K will be swapped with the main 64K, so you can then test the 2nd column of 64K with Sys-Check, which might suggest specific chip(s) that are bad.

 

But best advice is to replace all MT RAMs wth a different brand for long term reliability. After time, more of the MT type may go bad.

474371312_130XESwappedResistors.thumb.jpg.5a31f1e6eccfe8632a62ca5d8641b19d.jpg

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Yes. MT ram SUCKS. It has the propensity to not reset after power down. It holds chunks of data, like static ram. FYI- I have seen Atari put a good Japanese ram in the first slot, and the rest were MT. They were aware of this problem, and just tried to save a buck. To make matters worse, they would ship some units with the " terrible two " power supplies that were filled with epoxy. They would overheat, then when they went out, put out extra voltage and fry IC's, starting with the RAM. MMU's don't usually go bad. If the RAM passes, you may want to look into the PIA.

I am seeing more and more bad PIA's these day's, most being revealed by the official Atari 8 bit testing station I have. This program might reveal where th the bad RAM is.

 

Paul

Eightbitfix.com

atari-power-supplies.jpg

eXtended RAM test v0.21.0 (2003-09-16)(-XI-)(SK)(en)[128k].xex

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XRAM says "No XRAM detected!" and SHORTEST reports 131072 bytes of memory, but when I'm trying to start "Ext memory" the screen looks disorted and.. that's it. Nothing else happens.

I guess I'll try to buy the RAM chips somewhere and I'll try with the piggyback method first.

Worst thing is I don't really know where to look, which chip may be causing the trouble. Memory tester results I've uploaded to youtube shows some information as to which banks fail but I'm not sure how it corresponds to physical chips.

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BTW, do you the 130xe with 4 ram chips or the one with 16 ram chips? 

If you have the 4 ram chips it is pretty cheap and easy to replace the 2 extended  memory chips and check if every works ok. You can get those in ebay very easy. Like a pack of 5 just in case. You want to replace them all. 

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16 minutes ago, aquaz said:

I've uploaded to youtube shows some information as to which banks fail but I'm not sure how it corresponds to physical chips.

Banks do not correspond to chips at all. 1 byte of RAM is comprised of one bit from each of the 8 chips. You'd have to work out which bit of the byte is bad, and figure out which chip that corresponds to.

 

The only RAM testers that I know that identify corresponding chips are that built into the sys-check board, and Shoestrings memory tester, which is a just replacement OS ROM. I could program an EPROM with that on it and mail to you if you like.

 

https://atariage.com/forums/topic/282022-shoestrings-atari-8bit-ram-tester/

 

https://www.jammarcade.net/shoestrings-atari-8bit-ram-tester/

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28 minutes ago, manterola said:

BTW, do you the 130xe with 4 ram chips or the one with 16 ram chips? 

No I have the older(?) board with 16 4164 DRAM chips.

As far as I can see they're widely available and not very expensive. I'll try to put the them in sockets too.

13 minutes ago, Nezgar said:

I could program an EPROM with that on it and mail to you if you like.

Thank you, but I think those chips will be cheaper than international postage costs and taxes :D

 

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out of interest - what is the second monochrome screen test you ran?

 

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I haven't had much luck identifying bad DRAMs using the piggyback, I've had some success identifying bad SRAM ( 2114s, 2128/6116 ) with that method. The mT DRAMs I've dealt with have mostly shit themselves to the point where the chip is completely dead or the outputs are floating, I haven't really seen any other failure modes beyond that with these ones. 

 

 

 

Edited by shoestring
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20 hours ago, aquaz said:

No I have the older(?) board with 16 4164 DRAM chips.

As far as I can see they're widely available and not very expensive. I'll try to put the them in sockets too.

Oh.. OK that is not great but at least you can just cut the legs of every ram chip you want to remove and then desolder those legs one by one. It is not that terrible if you do it that way.

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yes, be aware that the XE circuit board are fragile and prone to lifting traces so take extra care to succeed

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I don't even have the parts yet and I'm already sweating.

I'm not sure about cutting the legs though - there's barely any space to fit the cutters, I tought about desoldering chips, removing as much solder as possible and then very carefully removing chips from the board.

I don't care about those old chips too much, but I'm worried I might cause more damage with the cutters than without them.

 

Edited by aquaz

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I've never had a problem getting the cutters in, what type are you using?

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If you'd like to minimize desoldering & cutting, I again recommend running the RAM test using a sys-check board, or shoestrings ram tester replacement OS ROM to first isolate specific chips to target...

 

My offer to send you a chip programmed with shoestring's RAM tester still stands, total cost mailed to US would be $5.  Much cheaper to start with if you dont want to jump for a sys-check right away.

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On 1/17/2020 at 1:22 AM, aquaz said:

Built-in memory test passes with all green, but some of diagnostic applications I've managed to start are showing really weird results - depending on application I use and how many restarts I've made...
 

Just forget the internal memory test. First, the test on the first K is all fake, i.e. it always shows green and does not perform an actual test. Then, the test for the region that is covered by the self-test overlay ($5800 to $5c00) is also all fake and does not test anything, just lights the square green.

 

Then, the test is not quite a test. It writes a byte, and immediately read it back. However, a typical failure pattern for dynamic RAM is that bits are flipped randomly after a while, i.e a better test would be to write all bytes, then wait a while, then read them back.

 

Last, the test tests the RAM byte-wise, but the RAM is organized bit-wise, i.e. each bit is in a separate chip, not each K block. Thus, it would be much more helpful to have eight blocks, each representing one bit, and belonging to each of the chips.

 

Long story short: Just forget the outcome of this test - it's worthless.

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I did it. Fortunately it was the second one I decided to replace.

Removing is not an easy process, putting a new one is pure joy.

It works now - programs show both base and extended memory.

 

atawymianapamieci.jpg

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good job but all that MT memory is living on borrowed time..

on a rainy day you ought to finish them off if you can

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