exxos's Atari, Amiga & retro forum

sety wrote: 05 May 2025 10:25 Hi guys. Just a bit of an update and a question.

I've gotten myself in a quite of a state with the Left/Right polarisation of the SIMM sockets and I'm not sure if I have stuffed in the right ones. Do your spring clips face North (toward CPU) or South (toward ISA bus) - On mine, the spring clips face North but the chips face South as they should.

Does it make any difference as long as the SIMM card is oriented correctly?

I've got myself so confused :?

As mentioned, the 72 pin SIMM sockets have 3 locating lugs that stick out on the bottom. 2 larger and 1 smaller so that they will only go in one way. I just checked my spares, and I have 72 pin SIMM sockets that face in both directions. I tested the ROM with both SIMMs and it faces the ISA sockets in both type of SIMM socket.

I would say that as long as you RAM and ROM modules are facing towards the ISA sockets and away from the CPU, you should be fine.

Here is a photo from my build for reference.


And here is the spare socket I checked (same as yours), noting the black SIMM socket is the other way round (in the foreground) and both sockets only fit one way round:

kodak80 wrote: 05 May 2025 12:32 As mentioned, the 72 pin SIMM sockets have 3 locating lugs that stick out on the bottom. 2 larger and 1 smaller so that they will only go in one way. I just checked my spares, and I have 72 pin SIMM sockets that face in both directions. I tested the ROM with both SIMMs and it faces the ISA sockets in both type of SIMM socket.

I would say that as long as you RAM and ROM modules are facing towards the ISA sockets and away from the CPU, you should be fine.

Here is a photo from my build for reference.


And here is the spare socket I checked (same as yours), noting the black SIMM socket is the other way round (in the foreground) and both sockets only

With the programmer from agarland and the board I can use any 72 pin socket as long as it is correctly placed? The Left polar sockets are expensive and hard to find.

I'm closing in a lot faster than I expected. I'm checking my shitty TSSOP solders. First boot is coming up sooner than I thought and the anxiety is real!

Okay wow, here I am. There is not much more I can do until I attempt a boot.

I don't have an ISA video card yet, but I have one on order. Should I use that as an excuse to procrastinate more and double check things over the next week? Or should I hook up the serial terminal, grit my teeth and hit the power switch? :lol:

I did something silly and accidently put a RAM module into ROM the programmer. Is this likely to cause any damage? I was going to mark it but didn't and it got mixed up again, but I know it isn't the one that is fitted.

(Chris/Exxos, if that particular 68060 looks very familiar it is because it is, and I sure don't want to smoke it!)

Thanks again guys. I am really enjoying this build!

- Stuart

That looks crazy good!

I did something silly and accidently put a RAM module into ROM the programmer. Is this likely to cause any damage?

No should be fine, they have exactly the same pinout so you just ended up writing a bunch of stuff to ram :)

Should I use that as an excuse to procrastinate more and double check things over the next week? Or should I hook up the serial terminal, grit my teeth and hit the power switch? :lol:

If you want to be extra cautious you could perhaps power up without cpu inserted, and measure that 3.3V and 5V are as expected on the board (and even -5V, +12V and -12V while at it; these are easily accessible on ISA pins)
Perhaps especially verify that power pins on the cpu socket have the correct voltage.
I did something similar when I built my boards, testing the power stuff at some stage of the build before turning it on with cpu inserted.

agranlund wrote: 13 May 2025 13:43 That looks crazy good!

Thanks! It means a lot coming from the dev :)

If you want to be extra cautious you could perhaps power up without cpu inserted, and measure that 3.3V and 5V are as expected on the board (and even -5V, +12V and -12V while at it; these are easily accessible on ISA pins)
Perhaps especially verify that power pins on the cpu socket have the correct voltage.
I did something similar when I built my boards, testing the power stuff at some stage of the build before turning it on with cpu inserted.

Ahh sweet! I already had a chance to do that when I flashed Nessi and everything measured up fine, so I guess I'm good to go!

- Stuart

Wheee! First boot, no smoke and something meaningful on COM1. This is far as it goes before it stops. I don't have an ISA graphics card yet, but I am happy that CPU seems to be talking, even if it is a bit grumpy and wants to halt!

This is way easier to work on than a Falcon! :lol:

An absence of smoke or explosions is indeed a good sign :)

So it prints
RAVEN060
...
InitMfp
RAVEN060 (again, and then halts?)


InifMfp will be the first time it's reaching out to stuff beyond the MC68150, so it feels plausible it could be related to that.
(it will write a bunch of stuff to the MFP1 and MFP2 registers)
Can't off the top of my head think of anything obvious that would cause it to end up executing code from the beginning of rom again though. Address pin short?

Perhaps the attached rom will get you to the monitor program. Its skips all but bare minimum initialisation.
Might be useful for poking at the machine to see how it behaves.

This safemode rom doesn't set up the Atari-like logical memory map so talking to stuff requires using their physical addresses.

agranlund wrote: 16 May 2025 19:31 An absence of smoke or explosions is indeed a good sign :)

So it prints
RAVEN060
...
InitMfp
RAVEN060 (again, and then halts?)


InifMfp will be the first time it's reaching out to stuff beyond the MC68150, so it feels plausible it could be related to that.
(it will write a bunch of stuff to the MFP1 and MFP2 registers)
Can't off the top of my head think of anything obvious that would cause it to end up executing code from the beginning of rom again though. Address pin short?

Oh sorry! It isn't executing from the start of ROM again! That's just me resetting without clearing the terminal buffer. I would really be scratching my head if it were behaving like that!

I'm feeling a bit paranoid about those MFPs now, since they came off eBay and I didn't socket them.

Thank you for the attached ROM. I will try it and let you know!

- Stuart

The monitor works! I have no idea what to do with it tho :lol:
Update: typing rtc into the monitor crashes the system