exxos's Atari, Amiga & retro forum

I've been playing with the PiStorm Atari this morning with the Pi3 instead of the Pi4.

Still no use as I was finally was able to make out the latch/flop-flop chip designations as 374 rather than 373 types.

Anyway not fun ensued setting most of the ST-RAM to be virtual... until I bumped the machine... Then it didn't work until I tapped on the MMU.... So I reseated it... wrongly as I mistook a crunched corner to be the one marking the pin 1 side... Wondered why the PSU kept resetting... Bother!

One dead MMU.

P.S. Or not.... Phew! Cruddy socket!

You know, the Kaico edition of the OSSC is a bit pants on the sync input side.

For a lot of the afternoon I was chacing what thought was an issue with the ST. When running with the TF536 as soon as it would get to the desktop the display would go off and the OSSC would be showing wildly changing horizontal sync values. Which would generally not happen when running with the 68000, so obviously it must be an accelerator problem, right?

Every time in medium res I'd open a GEM window the screen would go off... every time. I thought machine had crashed.

However, this is not the case. It looks like the Kaico OSSC is seeing the lines on the windows as spurious H.Sync pulses somehow and it's getting confused. Why not under TOS 1.4 then? Well, that doesn't have the dithered desktop background.

Putting a 'scope on the H.Sync signal shows if rock solid when the OSSC is going crazy.

My original OSSC has no problems with the signal at all.

I'm guessing that they cheaped out of the low pass filter on the h.sync line so it's seeing all the individual pixels.

stephen_usher wrote: 19 Feb 2026 12:55 I've completed the video. I decided against the extended edition as that would almost be as long as "The Fellowship of the Ring" extended edition. :-)

Anyway, here it is:

Hey Stephen, just wondering what you set the jumpers to on your Lazarus. I tried to see in the video, but I may have missed it.

Interestingly I installed the resistor and cap on the edge connector almost identically to you before I watched your video :)

According to the Lazarustorm Github the settings are:

Stock jumper settings for the LAZARUSTORM adapter, tested with two 68000 cpu's are: VPAJP 2-3 and BRJP open.

stephen_usher wrote: 28 Feb 2026 17:50 According to the Lazarustorm Github the settings are:

Stock jumper settings for the LAZARUSTORM adapter, tested with two 68000 cpu's are: VPAJP 2-3 and BRJP open.

Cool thanks

@stephen_usher

Can I ask where those blue sockets came from?

I was about to test my Lazarustorm and I cannot plug my Pistorm adapter into it at all it's just way too tight and needs way more force than I'm prepared to use.

My Pistorm adapter has turned pin headers so I'd expect it to fit, but I'm going to have to pull the socket and fit turned pin headers instead.

Will let you know how I get on,

They're from Retro Revival.

Turned pin will push in but as you probably saw in the video I had to push very hard the first time, removing the PCB from the case. After that it was far easier. See 32' 40".

I couldn't get the PiStorm adapter to push into the socket at all, so ended up swapping out for turned pin headers that work perfectly.

However for me the Lazarustorm wasn't working, at least not as intended, as I've described below.

I put the original CPU from this machine back in to test and the machine boots to the KS prompt with no issues.

I shorted JP6 on my Rev 6a then plugged in the Lazarustorm using the stock jumper settings of VPAJP 2-3 and BRJP open.

The machine started and I got an Emu68k boot screen from the Pi, and that's as far as it went. It just freezes. The RGB2HDMI is clearly powering up as I see profile info pop up briefly there, but no video activity.

However if I pull the original CPU from the A500 the Lazarustorm will boot fully and work as intended.

I tried all combinations of Lazarustorm jumpers but it made no difference, it would only boot from the external PiStorm with the original CPU removed.

I also removed the short from JP6 but that made no difference either. I put the short back to continue testing.

As soon as I installed the PiStorm back inside the A500 all was well.

So I dropped in a different CPU, and that worked fine. Ok, odd but lets try the original CPU again. OK that works now as well!!!

:dizzy:

From that the only thing I can possibly suspect is that JP6 was not shorted correctly and the act of clearing it of solder and re-jumping with a fresh solder blob worked. It's running just fine with Caffeine O/S and dual screens.

All a bit weird really...

So it all works just fine is the final takeaway, but it wasn't as straightforward as it could have been.

Sometimes the system needs a soft reset to get itself working for some unknown reason with the PiStorm in the Lazarustorm, but after that it's completely stable.