Atari 520 STE memory problem

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joska
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Re: Atrai 520 ste memory problem

Postby joska » Wed Mar 06, 2019 8:11 am

Lets not fuel the SIMM-myths - these are the requirements for STE SIMMs:

- It must be 30 pin SIMMs.
- Capacity either 256Kb or 1Mb.
- Speed 120ns or faster.
- All SIMMs must be the same *size*.

Manufacturer doesn't matter, 2, 3, 8 or 9 chips doesn't matter, parity doesn't matter. No problem in having four completely different SIMMs as long as the four requirements above are met. Oh, and the SIMMs must be in working order. That's not always the case today with 25+ years old components.

Greenious wrote:In short, my STEs has worked with just about every (working) 256kb/1mb simm I've thrown at them.


This sums it up nicely :)

athensnet wrote:I have tried also with 4 simms of 256 K to make it 1 MB but still the same problem.


I think we can rule out the SIMMs, there is most likely a problem with the STE. Time to dig out the schematics and multimeter I guess. I would start with the SIMM sockets and check continuity from there. If all the lines checks out (and the sockets themselves are undamaged) I would suspect the MMU/GLUE (combined in a single chip in the STE) or shifter next.

Edit: Running YARTT in manual mode as adviced above would problably give some hints to where the problem is.
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athensnet
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Re: Atari 520 STE memory problem

Postby athensnet » Sat Mar 09, 2019 5:39 pm

I think Joska is correct the bloody machine wants a profesional check.
I have done all what was proposed, even the poolfix one. The Yaartt with M selection and the upper memory address is always gives constant errors
I have three sets of simms Four the same from my other STE with 4 pieces of 1 MB from Freakz, the two ones 512 KB that came with the 520 STE and and another set of 1 MB in total.
All combinations of the sets and even unorthodox ones gives the same amount of memory available 270 KB.
The only difference which it happens only the time when I put two sims of the 1 MB in positions 1 and 3 I get a white picture with some coloured pixels or black and white stripes. The machine is stacked for a while and then it sounds like the tos is loaded and this because the cursor appears and are more coloured pixels populated and then the machine is stacked.
Pleas check the photos attached : https://www.dropbox.com/sh/dey2r6cjkq0w ... QBaLa?dl=0

6BQ5
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Re: Atari 520 STE memory problem

Postby 6BQ5 » Sat Mar 09, 2019 7:34 pm

Just took a look at your pictures.

You know what I would do? Replace the power supply.

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neanderthal
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Re: Atari 520 STE memory problem

Postby neanderthal » Sat Mar 09, 2019 8:17 pm

Yeah,I think I am on same path as Greenious here.Wonky adress line or something to ram.Might check the resistors there.
The ones in line with MAD0-9,ie R454-466?,,hmm,,sitting with a old bad paper copy here.R454-468,exluding 456,459,463,467 as it looks.
They should be 68ohm ones all of them,the 33ohm ones are for CAS,RAS and WE.Located between GSTMCU(U400) and Dram sockets.
Easy to spot they are inline sort of.
Anywho,got sort of a similar weird problem with a old ST.It booted fine with a desktop and so on.
But the damn thing would not properly load fats and or programs from floppy.(ye ye even I thought,what a 'bad' dma?)
And even started to fault trace properly,just to after a while figure out that the sockets had gone real dodgy.
My old standard push'em in and wiggle didn't work and was fooled by that.
Had to actually pull'em out and in to get rid of the oxide there.

Not of course appliacable to a STE but same sort of problem by the sound of it.

czietz
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Re: Atari 520 STE memory problem

Postby czietz » Sun Mar 10, 2019 7:46 am

Would have been nice to know the error actually shown by YAARTTT in "manual" mode.

athensnet
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Re: Atari 520 STE memory problem

Postby athensnet » Mon Mar 11, 2019 7:40 pm

@czietz
Please find below videos from the erros :
https://www.dropbox.com/sh/ehnmeblk518y ... g-eLa?dl=0
As you can see bombs and patterns and in the best case the scrolling error page (number 4 video)

czietz
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Re: Atari 520 STE memory problem

Postby czietz » Mon Mar 11, 2019 7:57 pm

You're not entering what I asked you! Type 080000 when asked for the start address. Then press Enter. Then type 3FFFFF when asked for the end address. Then press Enter.
I see you typing "08000 3fffff", which is a) missing one "0" in the start address and b) all in one line. It's no wonder YAARTTT crashes or shows strange errors in this case.

athensnet
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Re: Atari 520 STE memory problem

Postby athensnet » Mon Mar 11, 2019 8:25 pm

Thank you for the reply.
I thought I was doing it correct.
Upon pressing the "M" the start adrees is automaticaly typed as 0x. So there to put the 080000 after the 0x?


czietz
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Re: Atari 520 STE memory problem

Postby czietz » Mon Mar 11, 2019 8:59 pm

What looks at first like random stuff, is actually often an opcode. E.g. I see that often 0xb5c0 is read, which is an opcode from within YAARTTT's test loop. This most likely means that the MCU (GSTMCU in the STE) is not even accessing RAM above 512 kBytes. Therefore it reads back whatever happens to be on the data bus -- in this case opcodes from the program code. I would check the RAS and CAS traces and resistors next.


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