Pi400 won't boot RISC OS at all!

I just got a new Pi400 (UK) from Digikey. It works fine with Debian, but I actually bought it because I thought it would make a nice RISC OS machine. It seems I was wrong!

I simply can’t get RISC OS to boot at all.
I have tried the Pi400 install from downloads here.
The Pi400 install from RO Direct.
Updating my Pi3B install with the update file from RO direct.
Many different SD cards from different manufacturers.
A different PSU.
A different HDMI cable.
Network cable plugged and unplugged.

Regardless the behaviour is always the same. A quick flash of a mostly textual boot screen.

Then the pi outputs a black screen at 1650×1050 60hz (correct for my display) and absolutely nothing else.

Any suggestions? Thanks!

Both the ROOL and ROD RPi400 images worked out of the box here on the RPi400. RISC OS works very well on the RPi400 with a commendable turn of speed, it is a most satisfactory piece of kit.

A quick flash of a mostly textual boot screen. Then the pi outputs a black screen at 1650×1050 60hz (correct for my display) and absolutely nothing else.

Given that there is some initial display it could be worth trying an easy one first. Press F12 then unseen enter *wimpmode 28 to evade any EDID issue but but if that were the case then the monitor would not even show the black screen.

It’s not that the monitor may be connected to ‘wrong’ hdmi output as that only loses sound. (The ‘right’ hdmi is the one nearest the SD card slot.)

The RPi400 builds are not exclusive to the RPi400, they exist as separate entities because the RPi400 comes after OS5.28 which needed to be minimally updated for the RPi400, anywhere else it would be called OS5.28.1, and they should also work in the the RPi3B. My RPi400 card starts up in the RPi1. (It has stopped at a “Memory cannot be moved error” but that will be because a greater the 512MB RAMdisc is configured.) The ethernet would need to be reconfigured. The RPi3B card would need minor changes to work on the RPi400.

Just noticed something.

1650×1050

Is that correct?

Another possibility is that the RPi400 is a new revision we don’t know about yet.

Does RISC OS support horizontal resolutions which aren’t divisible by 8 these days?

Does RISC OS support horizontal resolutions which aren’t divisible by 8 these days?

I was unsure, so I raised the query.

I have now tried a 1650×1050 mode on the RPi400 and it is displaying, on a 1920×1200 AOC. The cvt tool would only create 1648×1050 so there was a little creativity applied to the MDF.

So its probably not that then.

So its probably not that then.

Something else it probably isn’t is an unexpected board revision. The revision number is displayed near the top of bootloader screen when no bootable media is found. Mine is c03130. Just in case.

Sorry 1650×1080 was a mistype. The correct resolution is 1680×1050.

But I have news! I tried the Pi400 on two more of my displays: a FullHD Samsung monitor and a 4:3 Dell. I had to use a HDMI>DVI cable. The result was exactly the same.

Then I took the Pi through and disturbed my wife’s TV viewing in the living room. That is also a Full HD Samsung. However on that I did get the RISC OS desktop. It was oversized and the TV wouldn’t adjust to it. However I was able to change the congfig to a default resolution of 1680×1050 and save. Now going back to the original display I get the desktop displayed very nicely indeed.

But I guess, based on the number of displays that I got a black screen on to begin with that the default “Native” resolution doesn’t work properly, either for a lot of displays or I am just very unlucky with the ones I have available!

Thanks all for your help :)