The Sinclair QL Forum

Looking in to this further I found this video.

https://youtu.be/0z4X4AMKlcs

What is the easiest way to get a Minerva ROM?

maigretnz wrote:As it may be a RAM issue I used my phones thermal imaging camera to monitor the temps of the chips.

That was a good idea and it would be useful if someone else provided a thermal picture of a working board for comparison. By parallax I assume you mean the yellow hot areas need to move up one chip since the bottom ones are not on chips. The picture does show that one bank of RAM chips is running cooler than the other which might mean one of them is loading or more likely blocking signal switching. Switching creates the heat or even selection of the chips might be duff so they take less power. The first picture of your post looks like a lot of display ram chips are taken out because I had one duff ram chip but the display could still show the address that was wrong. Not sure why you want to change the ROM since it looks like display memory or selection of it that is at fault I think, although I am not an expert on QLs.

Ruptor wrote:

maigretnz wrote:As it may be a RAM issue I used my phones thermal imaging camera to monitor the temps of the chips.

That was a good idea and it would be useful if someone else provided a thermal picture of a working board for comparison. By parallax I assume you mean the yellow hot areas need to move up one chip since the bottom ones are not on chips. The picture does show that one bank of RAM chips is running cooler than the other which might mean one of them is loading or more likely blocking signal switching. Switching creates the heat or even selection of the chips might be duff so they take less power. The first picture of your post looks like a lot of display ram chips are taken out because I had one duff ram chip but the display could still show the address that was wrong. Not sure why you want to change the ROM since it looks like display memory or selection of it that is at fault I think, although I am not an expert on QLs.

The youtube clip I quoted said the Minerva ROM had more POST dianostics on boot up to give more indication of what may be the issue

maigretnz wrote:The youtube clip I quoted said the Minerva ROM had more POST dianostics on boot up to give more indication of what may be the issue

I didn't notice that you purloined the thread started by Mselkin that confuses things. It would have been better to start your own thread for your fault. We have no idea what your problem looks like on the screen since the screen that started this thread is not yours.
You need something like this to get minerva
https://www.theqlforum.com/viewtopic.php ... tor#p33779

I think the hotter RAM bank may simply be down to the fact that video access that bank of RAM and never the other - even with dual screens enabled, and since that video RAM access is pretty much constant whilst the device is on (apart from flyback time), this could easily account for the chips running hotter.

Sorry if it looks like I took over this thread but the failure I have appears to be the same as the original post so I was trying to avoid 2 threads.

Pr0f wrote:I think the hotter RAM bank may simply be down to the fact that video access that bank of RAM and never the other - even with dual screens enabled, and since that video RAM access is pretty much constant whilst the device is on (apart from flyback time), this could easily account for the chips running hotter.

All chips are accessed during screen refresh because it also doubles as the DRAM refresh.

maigretnz wrote:Sorry if it looks like I took over this thread but the failure I have appears to be the same as the original post so I was trying to avoid 2 threads.

The original post was a picture of a minerva screen not original ROMs like your machine hence my confusion with two different problems. Perhaps your infrared picture is a pointer because of the following.

mk79 wrote:All chips are accessed during screen refresh because it also doubles as the DRAM refresh.

Does this mean the infrared picture is pointing to a RAM bank selection problem or is it still a difference in RAM access rates due to code using one area more?
It would be useful for future fault diagnosis to have a heat picture of a good unit for comparison.

mk79 wrote:

Pr0f wrote:I think the hotter RAM bank may simply be down to the fact that video access that bank of RAM and never the other - even with dual screens enabled, and since that video RAM access is pretty much constant whilst the device is on (apart from flyback time), this could easily account for the chips running hotter.

All chips are accessed during screen refresh because it also doubles as the DRAM refresh.

true - but not all RAM chips will be accessed when the image is being written in screen RAM - so one bank may still run hotter

Ruptor wrote:

mk79 wrote:All chips are accessed during screen refresh because it also doubles as the DRAM refresh.

Does this mean the infrared picture is pointing to a RAM bank selection problem or is it still a difference in RAM access rates due to code using one area more?
It would be useful for future fault diagnosis to have a heat picture of a good unit for comparison.

Actually I've had a look at it again and while it's true that both banks are refreshed at the same time during screen read, only bank 0 actually provides data, bank 1 does a "RAS only refresh". So bank 0 will experience more activity, also because it hosts the system variables and probably everything else that is needed for an idling QL (code is generally executed from ROM in this case). One could try poking an endless loop executed in supervisor more to address $30000 to see if that changes the temperature of bank 1... but even though my employer has several expensive FLIR camera I haven't been at the office for 8 months now, so can't try it myself