The Sinclair QL Forum

That being said you must not completely stop toggling RAS because it is used for the internal charge pump to negatively bias the substrate of the DRAM chips, without which the DRAM might consume too much current and not work right (a quirk of those older DRAM chips). Yes I forgot we discussed this ...

With the shadow ram I used the dram refresh is no more slowing the video ram access because it is done in the same time the ula reads the data to draw the screen and does not extend it at all. That is why I got about 30% speed increase in video ram access. The only way to do a little better if you ...

Looking closely at the VESA standard, the +5v line is not powered by the monitor, it is an input instead. In this case the D2 diode can be omitted. Anyone can confirm my guess? Confirmed. It could makes sense to modify a cheap monitor to provide 5V output. But in that case, the diode better goes in...

Yes the standard video ram can be replaced but there is no point to do so (that is what I should have said). I agree inasmuch great speed can not be achieved with the 68008 anyway. And for myself, I see no point in optimizing it. But if the 68008 system is to be optimized, replacing the video RAM c...

The ULA gets 18 of the 20 address lines, so without extra connections it's limited to the original 128 KB of RAM. Yes, but that wouldn't hinder replacing the video RAM. Also the ula sees the 16 lower bits of the address bus multiplexed 8bits at a time, so even with A18 and A19 available memory acce...

To be able to replace the video ram one needs to use more signals than the ula socket provides so I just did this simple improvement. I'm sure you are much more into this than me. If I remember correctly, the ULA can see all the signals of the QL DRAMs. Plus it can deactivate their RASL/CASL. So at...

I've finally found some time to tweak some demo code I've had for a couple of years and make a video out of it that shows the extended QL graphics idea: [youtube]https://www.youtube.com/watch?v=7EizW3ZWNqc[/youtube] Great presentation video. I was wondering about the voice until it turned out to be...

Hi Gianni, In the later versions, the one with the smaller PI, the 100 ohm resistors are missing and the syncs are directly wired to the VGA connector. Is that correct or do I need to add the two resistors between GP16,GP17 and the VGA v-sync and h-sync ? It is correct, and tested in several VGA des...

I have already checked the replacement for DRAM 1Mx16 chips, as well as for the SIMM 72 module, they work fine. That is good. I want to try adding support for QL-SD. Sounds like a good idea. Although it looks a little strange to use the old driver for the ROM port, I think that modifying the QL-SD ...

Yes, recently I was able to solve the INGOT20/21 problem. Amazing. To reverse engineer the SGC logic without sourcecode is a fantastic achievement. Congratulations and applause to you! :D It is also a very beautiful board. I like that you are using through-hole components whereever possible. Keeps ...