STE BAD RAM (not bad simms)

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Re: STE BAD RAM (not bad simms)

Postby dlfrsilver » Mon Jul 04, 2016 2:27 pm

unfortunately Chris i don't have any. How much does this cost ?
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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 2:31 pm

dlfrsilver wrote:unfortunately Chris i don't have any. How much does this cost ?


Not sure, Normally around £30 I think, actually I have a huge stack of them, but no time to test them out. I want to convert them as a universal test cart, but not enough hours in the day :(
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Re: STE BAD RAM (not bad simms)

Postby czietz » Mon Jul 04, 2016 3:59 pm

I think I can easily write you a test program that selectively fills the screen memory alternating with two test patterns, e.g. white and green, at maximum speed and then reads back the memory. Do you want the program to stop if there is an error? (If the program is supposed to continue running, any error message on the screen of course will be immediately overwritten.)

Since you mentioned GEMBENCH and the window test: Do you know if the Blitter is used there to fill the screen? Maybe the problem is more pronounced when the Blitter and not the CPU is doing the writes.

PS: On your screenshots from the diagnostic cartridge I see that the error addresses are spread out with no particular accumulation at higher RAM addresses. Contrary to your post, the first megabyte is also affected.

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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 4:14 pm

czietz wrote:I think I can easily write you a test program that selectively fills the screen memory alternating with two test patterns, e.g. white and green, at maximum speed and then reads back the memory. Do you want the program to stop if there is an error? (If the program is supposed to continue running, any error message on the screen of course will be immediately overwritten.)

Since you mentioned GEMBENCH and the window test: Do you know if the Blitter is used there to fill the screen? Maybe the problem is more pronounced when the Blitter and not the CPU is doing the writes.

PS: On your screenshots from the diagnostic cartridge I see that the error addresses are spread out with no particular accumulation at higher RAM addresses. Contrary to your post, the first megabyte is also affected.


I didn't pay much attention to the address, but using 1MB of total RAM seems to not show up the faults, at least not on screen ram. Its possible lower ram could be effected, but mostly its 4MB and screen ram I have seen most faults. So its a good starting point.

I'm not sure if the blitter is used to fill the screen.. Its all just AES calls. Likely it does. Probably using the blitter would help speed up the loops ?

As for errors, might not need to test the entire screen area. Could possibly have a error line of text reporting number of errors, possibly how long the test has been running in hours and minutes aswell. That can update after say 10 or 100 ram test cycles so it doesn't slow down the ram test loop.

White and green is where I see the errors, when the background goes from white to green, I see small pixel lines drawn which seems to be white. I tried to get a image, but they happen so fast and the with video compression just impossible to see visually.

So my idea is to fill the screen area with green, and read it back to see if it is still green. Possible then fill with white and could read that back aswell, then loop back to green fill and read that back. Likely the colour wouldn't matter, could even be random. Though the pixel lines I see I am assuming its picking up "white" or assume again $FF from somewhere else in RAM causing the white pixel lines.
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Re: STE BAD RAM (not bad simms)

Postby stimpy » Mon Jul 04, 2016 5:34 pm

How about driving a signal when a fault occurs so you can trigger your scope? Something fast, maybe a read in the rom port address range and use the active low ROM3 or ROM4 signal.
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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 5:39 pm

stimpy wrote:How about driving a signal when a fault occurs so you can trigger your scope? Something fast, maybe a read in the rom port address range and use the active low ROM3 or ROM4 signal.


I don't know how that would work ? I can scope the MAD lines, but no way to know when the fault happens as dont know what or where the fault is exactly.
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Re: STE BAD RAM (not bad simms)

Postby czietz » Mon Jul 04, 2016 6:13 pm

Please find attached my crude screen RAM testing program. It alternatingly fills the screen memory with two colors as fast as it can, reading back the memory and comparing. I hardly doubt that you can see something with all the flickering. (Don't stare too hard if you're sensitive to flickering colors :wink: ) The colors are: black and white for mono (duh!), green and white for medium res, magenta and white for low res. This corresponds to 3 different test patterns, BTW. Blitter is not used at this time, let me know if you need this.

The status line shows the number of iterations, the number of iterations where an error occured and the RAM address of the last error. When no error is found, the number of iterations is only increased every 256 runs to save time. Press and hold the Alt key to exit the program.

I hope this suits your needs.
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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 6:27 pm

Thanks very much! See what you mean about the flicker, though I have been watching similar for the past week, so its already caused me brain damage :)

I've dismantled another STE, and its the same motherboard, so trying it out on that. Though looking at the signals they look pretty good on this one. Though a chap on FB said hes seen the spikes on his STE. So not sure what the difference is between these machines.
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Re: STE BAD RAM (not bad simms)

Postby Maeke » Mon Jul 04, 2016 6:54 pm

I know there are at least two different revisions of this integrated ic (c302183), i have the c302183-001 and i have seen a c302183-002/B on ebay, so finding exactly the same motherboard could be tricky Chris, maybe you should check the ic revisions you have (if one of these revisions is bugged, it could explain your problem).
Of course it's just an idea, i can't say for sure this is the answer (and i doubt it anyway, but who knows?).
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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 7:06 pm

Maeke wrote:I know there are at least two different revisions of this integrated ic (c302183), i have the c302183-001 and i have seen a c302183-002/B on ebay, so finding exactly the same motherboard could be tricky Chris, maybe you should check the ic revisions you have (if one of these revisions is bugged, it could explain your problem).
Of course it's just an idea, i can't say for sure this is the answer (and i doubt it anyway, but who knows?).
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:)

I've got another motherboard looks the same, same number on the IC, but that one seems to work fine. Also tried one without internal blitter, on power up the signals were bad, but after a moment went good. Still not all lines are perfect, but its passing RAM tests. Also I've heated up both these "new" motherboards a fair bit and they still are not faulting.

Theres a chap on FB who had a similar issue where loading the linse with a scope caused screen corruption, so his motherboard has similar issues to mine, but these 2 new boards dont have the scope loading issue. So this is really confusing things now :roll:
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Re: STE BAD RAM (not bad simms)

Postby czietz » Mon Jul 04, 2016 8:29 pm

Please also find attached another test program for the screen memory. This implements one test of the renowned Memtest86, more specifically the "moving inversions, 8 bit walking ones and zeros", which is supposed to catch hard to find "soft" errors in RAM.

It is rather slow because at this time I didn't bother writing the inner loops in assembler. Long term plans including speeding it up, expanding the test area to (almost) all RAM and implementing more tests.
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Re: STE BAD RAM (not bad simms)

Postby exxos » Mon Jul 04, 2016 8:40 pm

Cool :) More RAM test programs are useful, well they are for me :)

I've tested out the external blitter board and no errors on your program or diagnostic cart. Now trying a identical looking board. I'm starting to think that for whatever reason that problem STE IC is just bad. The faults seem to come and go depending how hot the IC gets. Considering I've now tested some other boards, im not seeing the same amount of spikes, I do see some, but nowhere as bad. So maybe its just a bad IC. Possible they could have been a bad batch of IC's but testing out every STE I have is going to take a lot of time, and doesn't mean I will find 2 IC's with the same batch number either.
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Re: STE BAD RAM (not bad simms)

Postby Maeke » Tue Jul 05, 2016 9:47 am

Well, you could try to change this ic (i know it's probably smt like mine but you have better equipment than me), and see if the errors are still there, this way you'll know for sure if the ic is faultive.
This one is presumably new (never used) (uh?) http://www.ebay.fr/itm/NEW-Atari-520-10 ... SwGIRXYENJ
PS: i know you probably have your own stock.

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Re: STE BAD RAM (not bad simms)

Postby exxos » Tue Jul 05, 2016 1:31 pm

Maeke wrote:Well, you could try to change this ic (i know it's probably smt like mine but you have better equipment than me), and see if the errors are still there, this way you'll know for sure if the ic is faultive.
This one is presumably new (never used) (uh?) http://www.ebay.fr/itm/NEW-Atari-520-10 ... SwGIRXYENJ
PS: i know you probably have your own stock.


I did see that one, slightly different numbers so not sure its the same IC exactly. But would be cheaper to get a scrapper STE and take the IC off that, I don't really fancy messing about with SMT stuff like that anyway. Only need a slight solder bridge somewhere and the things fried again anyway.

Going by I've got a identical board with identical IC's, I can't attribute anything being faulty in general. One IC works, other doesnt.. I mean it could be a bad batch of IC's but similar problem with the DMA's, would need to test 100's of them, so its just not viable to investigate it.

Its possible the PSU was spiking and caused damage to it at some point in the past (before I brought the machine) So thats all I can really conclude at this time.
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Re: STE BAD RAM (not bad simms)

Postby czietz » Tue Jul 05, 2016 5:07 pm

Did you run one of my test programs on your known-bad STE of the original post, BTW? Did it find errors?

As I luckily don't have an Atari that suffers from bad RAM, I have no realistic way of checking that my RAM testing programs really work as intended. I did of course simulate errors with a debugger, but I'm keen to know if the tests also find real bad RAM.

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Re: STE BAD RAM (not bad simms)

Postby exxos » Tue Jul 05, 2016 5:36 pm

czietz wrote:Did you run one of my test programs on your known-bad STE of the original post, BTW? Did it find errors?

As I luckily don't have an Atari that suffers from bad RAM, I have no realistic way of checking that my RAM testing programs really work as intended. I did of course simulate errors with a debugger, but I'm keen to know if the tests also find real bad RAM.


I ran your program on the other test machines, also the one with bad ram. But the problem only showed up (at least with the diagnostic cartridge) after it had been running for 2 hours. So to speed things up I started heating up the IC with my gas soldering iron, as after a few seconds before it used to crash the diagnostic cartridge. But it seems I got it to hot while running your program and the screen went black and that was kinda it :roll: So I can't tell you if your program worked or not as currently I dont have a faulty ST :roll: .

But what I could do is remove a DRAM IC off one of the simms, then it will simulate a bad bit all though that address range. If its in the >1MB area then the machine should still run fine, but should show as screen corruption... and your program should pick it up. Though its not a totally fair test as the RAM fault I had before was intermittent/random.

I guess I could short out A9 to 0V while its doing the tests, that might be easier to try out..
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Re: STE BAD RAM (not bad simms)

Postby Maeke » Tue Jul 05, 2016 10:04 pm

exxos wrote:
Maeke wrote:Well, you could try to change this ic (i know it's probably smt like mine but you have better equipment than me), and see if the errors are still there, this way you'll know for sure if the ic is faultive.
This one is presumably new (never used) (uh?) http://www.ebay.fr/itm/NEW-Atari-520-10 ... SwGIRXYENJ
PS: i know you probably have your own stock.


I did see that one, slightly different numbers so not sure its the same IC exactly. But would be cheaper to get a scrapper STE and take the IC off that, I don't really fancy messing about with SMT stuff like that anyway. Only need a slight solder bridge somewhere and the things fried again anyway.

Going by I've got a identical board with identical IC's, I can't attribute anything being faulty in general. One IC works, other doesnt.. I mean it could be a bad batch of IC's but similar problem with the DMA's, would need to test 100's of them, so its just not viable to investigate it.

Its possible the PSU was spiking and caused damage to it at some point in the past (before I brought the machine) So thats all I can really conclude at this time.


Well i didn't mean it was a faulty version, but most likely a damaged ic, that's why i thought trying another on this motherboard should be done.

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Re: STE BAD RAM (not bad simms)

Postby Anzac » Tue Jul 26, 2016 3:13 pm

exxos, maybe the IC is giving problems due to heat generation.

i´ve encountered some PCs who gave memory errors and then i found the northbridge was heating up and causing the errors. putting a fan solved the problema (at least at the time).

i can loan you a FLIR ONE camera if you want. it´s really good to find out where overheating is occurring. my FLIR is iOS version not android.

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Re: STE BAD RAM (not bad simms)

Postby exxos » Tue Jul 26, 2016 3:28 pm

Thanks for the thought. Currently I just concluded it was a bad IC. Though I killed that machine (think I posted about it already) so I can't do anymore tests anyway :(

I still think there is something suspect with the RAM on all machines in general. I think it comes down to long running time with some "9 chip" RAMs. There seems to be conflicting views about Parity. IMHO as those datalines are left "floating" they can cause noise on the RAM, with the fact that the RAM signals are not great to start with, it looks like after some hours of running, things can start to trip up enough to cause RAM and possibly DMA related problems.

Of course more work needs to be done , but that would be down to the community to run the RAM test software for several hours and document if they have 8 or 9 chip RAM. Though I can't see enough data being collected to draw any sort of conclusion.

Though I have observed some 9 CHIP simms failing after a few hours running, and others do not. So at this point I would suggest caution to anyone fitting 9 chip RAMs into their STE.. With RAM problems hinting towards DMA problems also, with so many people adding 4MB RAM into their machines, a "bad DMA" could simply be a red herring for bad RAM.
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Re: STE BAD RAM (not bad simms)

Postby Lynxman » Thu Jul 28, 2016 8:40 pm

exxos wrote: So at this point I would suggest caution to anyone fitting 9 chip RAMs into their STE.. With RAM problems hinting towards DMA problems also, with so many people adding 4MB RAM into their machines, a "bad DMA" could simply be a red herring for bad RAM.


Maybe it will fix the problem if the signals only used for the Parity chip are connected to GND.
Some years ago i found a document which told it may result in some kind of trouble if this signals are floating.
Or just remove the Parity chip.


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