exxos's Atari, Amiga & retro forum

Hi guys,

In my attempts to upgrade the motherboard from 1 to 4 mb using an exxos I resulted in creating an Atari ST that provides a black screen when booting.
From this state I have soldered in sockets at the first rows of ram for further diagnosis. I am using RAM simms that I have succesfully tested using Yaart on another machine. During bootup, I get a black screen: When using the diag cartridge, I have the following screen: With the following output over RS232; wich are a combination of
I1 RAM/data line errors and
I2 RAM disturbance errors My first intended step is to consult the motherboard schematics to see if I can figure out if I can start testing continuity for all the related connected pins of the soldered in sockets.

I have no clue as to how to meaningfully interpret the Diagnostics cartrdige output to narrow down/focus/validate more specifically than mentioned approach. I would be oblidged to get pointers and feedback on my exploration :).

Kind regards,
Wietze

<edit> my current `diagnostics tools' consist of the cartridge and a multimeter.

Looks like bits 8 & 10 are bad. So if you trace on the schematic where D8 & D10 goto which chip and resolder it.

exxos wrote: 13 Jan 2021 22:21 Looks like bits 8 & 10 are bad. So if you trace on the schematic where D8 & D10 goto which chip and resolder it.

Thank you for your reply. How did you determine that bit 8 and 10 are bad? Id like to understand this.

In the meanwhile, I checked connectivity on all the soldered lines, by checking connectivity of the pin on corresponding pins on different sockets and unsocketed pins on the other rows. And from this I conclude that at least all pins are connected / the sockets are connected up with the board. I will see if I can trace the pins into the rest of the board; checking for continuity.

wietze wrote: 13 Jan 2021 22:30 How did you determine that bit 8 and 10 are bad? Id like to understand this.

Just count the bits https://www.exxosforum.co.uk/forum/viewt ... 143#p47751

See troubleshooting help.

But it look like bit 8 and 11. So after looking at schematics it is U44 and U27.

EDIT: @exxos beat me to it. :)

DoG wrote: 13 Jan 2021 22:49 EDIT: @exxos beat me to it. :)

Not really, you was more helpful ;)

Awesome guys! Thanks. Just to apply this knowledge (after reseating the simms):

So i ran the diagnostics a bit longer, just to see if I could make sense of it. And from the following shot I deduce:
D12 (from first line)
D9 and D8 and D2 (from second line)
D7 (from 4th line)
D14 (from last row)

These I1 errors come steadily after a bunch of I2 RAM Disturbance.
Is detecting errors in memory for I1 and I2 messages the same?

To be honest, if I run the diag cart for longer, it seems that almost all D lines are bad. There is literally lines that are 16 times 0, followed by 16 times 1; but these do not show consistently. (e.g. for reach 16 0's entry a different mask of 01 combinatios are shown per line).

If your getting random bit errors, then it can be bad RAS/CAS lines or bad address bit...

I fell victim of that recently... https://www.exxosforum.co.uk/forum/viewt ... 670#p37284

wietze wrote: 13 Jan 2021 21:21 I am using RAM simms that I have succesfully tested using Yaart on another machine.

I see no SIMMs there (SIMMs are used in the STe, here you have just chips in DIP packages), but what I see is the AT-Speed hardware emulator. Have you tried removing it?