Atari Mega ST 1 Rev 1 no boot

[rubber_jonnie]

Definitely looking like a RAM issue. I'd definitely recommend using a serial cable, it will tell you an awful lot about the RAM during boot.

One thing I would add here is that the Mega ST mainboards are pretty fragile, so handle with care, I had one board where I plugged an IDE adapter into the MegaBus connector and it popped 2 vias and broke it.

Quick question.... serial output only works with Diag cart on right? or a regular boot should show some output?

Just with the diag cart.

[Dwh18]

Hi
Not great output... get some artifacts in some tests but nothing special....One symptom I notice with the diag cart is that main menu takes ages to load

WhatsApp Image 2025-03-07 at 10.29.07_2cde6525.jpg

[HigashiJun]

Is everything correctly set ?

[Dwh18]

Is everything correctly set ?

I'm using 9600, N,1, and tried several control types ... HW, None, XonXoff

Any clue why Diag menu loads sooo slowwwww?

[HigashiJun]

@Dwh18

I use Putty with an USB to RS232 cable, with the following settings:

Baud rate to 9600 , 8 data bits, no parity, 1 stop bit and no flow control.

[Dwh18]

@Dwh18

I use Putty with an USB to RS232 cable, with the following settings:

Baud rate to 9600 , 8 data bits, no parity, 1 stop bit and no flow control.

With an adapter to convert DB9 to DB25?

[Badwolf]

Any clue why Diag menu loads sooo slowwwww?

Lots of errors?

It looks like you're getting a full character set dump (in ascending order) on your terminal so something's happening.

BW

(BTW, a floating [or toggling] HALT or BR line could produce slow motion output)

[HigashiJun]

With an adapter to convert DB9 to DB25?

No, there is no adapter.

The USB plugs directly into my USB port and the DB25 into the ATARI.

[rubber_jonnie]

@Dwh18

Baud rate to 9600 , 8 data bits, no parity, 1 stop bit and no flow control.

These settings are indeed correct.

You should see data on screen as the machine boots and you will eventually get a menu over the terminal that shows the same thing as on the computer screen.

Did you revert the RAM upgrade fully as yet?

[Dwh18]

Yes, all reverted ... but no onscreen duplicated on serial for sure