Atari ST 520+

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zChris
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Atari ST 520+

Post by zChris » Wed Sep 15, 2021 1:06 pm

Hello,

I have acquired one Atari ST 520+. It is a machine with 1MB memory and 1.04 TOS. I have a problem with it when it comes to UltraSatan. It recognizes the SD card and i can partition it. But when it comes to writing to it there are issues and sometimes the SD card gets corrupted.

I have been checking around the forum and the page for mandatory fixes, and the fixes it suggest are 10, 11 and 12. I assume that there is problem related to signals from DMA. There is also a GOTEK in the machine and i have not had any issues with that. The PSU is https://centuriontech.eu/product/st520psu/ .

So my idea is to do the mandatory fix 12. I dont think i need to change the CPU since ive gotten a new PSU.

Do you have any recommendations on what i can look at to fix this ?

/zChris

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Steve
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Re: Atari ST 520+

Post by Steve » Wed Sep 15, 2021 2:04 pm

Ah @zChris I feel sorry for you, you've just jumped down the rabbit hole of the DMA. Change all the data bus resistors to 2.2k, follow the guides... But just remember, even doing all this might not solve the problem.

By the way, something I found out about recently is the EmuTOS image that can be burned to an ACSI device SD card and boot 'outside' of the drive partition - it actually solved all read/write errors for me, here is the post:
https://www.atari-forum.com/viewtopic.p ... 49#p421449
And here you can download the images:
https://github.com/czietz/emutos-bootlo ... oot-loader

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rubber_jonnie
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Re: Atari ST 520+

Post by rubber_jonnie » Wed Sep 15, 2021 3:21 pm

Also, you'd need a DIP version of the HC, which I don't seem to see around much, which would mean removing the old package and fitting a socket.

As well as the data bus pullup change, you might want to add no 3 from the mandatory fixes to your list, it helped stabilise a couple of mine and is fairly easy to do.
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exxos
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Re: Atari ST 520+

Post by exxos » Wed Sep 15, 2021 4:12 pm

The HC CPU is for STE series. Adding a HC to STF type machines may well make matters worse.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~

zChris
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Joined: Fri Nov 27, 2020 10:13 pm

Re: Atari ST 520+

Post by zChris » Wed Sep 15, 2021 5:51 pm

So all I can do is the resistor upgrade?

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