The Sinclair QL Forum

Maybe this has been addressed before but does your implementation uses the same pixel/memory layout as the 16 colour Aurora mode ? François No, this is based on regular mode 8 except the original flash bit is used as a brightness bit. It means that for each pixel, two bits out of four are in the ev...

Pr0f wrote: ↑Sun Dec 04, 2022 7:44 am ... A winding with 500mH inductance would give a reactance of 157 Ohms.

...And that would be very low for a primary reactance of that size transformer. The primary inductance will easily be in the tens of H region.

Excellent work Leon! The black version looks better to me. The reason why composite will look bad is that the patterning produces a 2.5MHz frequency component which is not well filtered in the PAL coding process (Sinclair used a simplified circuit for the PAL modulation chip which does not filter ch...

The extra resistors should be connected to the voltage divider before the series capacitor connected between it and the actual RGB pins of the PAL chip. The extra resistor should be connected to the common point of the 8.2k resistor from the RGB signals and 1k resistor to ground, as well as the afor...

AFAIK the ATF1508AS can be used in place of EPM7128S (as used here ). But at about the same price (ATF1508 is largest in range). ATF1508S can also be had in a TQFP100 package which is small and thin, so much so that with a multilayer PCB it may be possible to squeeze the whole board within the outl...

Checked, mine is the old CLA2310 in a ceramic case, so perhaps one of the first ones...

What do you think about the big differences of the 2 ULA speeds ? Not sure, obviously some optimization was done, the difference in the required logic is very small. It makes sense that a small mask correction could be done between batches. That being said, I only have one type (will have a look an...

It is difficult to test the RAM speed with that simple program because most of the code executed runs in ROM. But you could for instance do a loop of scrolling the entire screen vertically, and then subtract the time an empty loop of the same length takes. This will still have lots of cycles in ROM ...

In the beginning I did the 8 cycle (of the 7.5Mhz clock) refresh for the non visible lines and tested the speed vs the ULA and for a simple basic program loop the time it took for the cpld was about 1' 17" vs 1' 15" for the ULA. Then I reduced the 8 to 4 cycles for the non visible lines a...

What I haven't really understood: How have you read the contents of the Ula to know, what it is doing? I studied Nasta's description of the ULA. It's totally accurate and I mentioned that at my fb post. Nasta is great, respect. Thanks, I wonder if it is possible to do a few small improvements when ...