ZX Spectrum 128K toastrack vs. Harlequin issue 2D timing differences

This week I’m preparing the first batch of Harlequin 128K kits, and I’m using the issue 2D for that.

Now some people asked if the Harlequin issue 2D has the exact same timings as the original toastrack has.
Some say the Harlequin issue 2D has 48 timings and thus is different, but others say issue 2D should have toastrack timing

So I ran some demos and games with border effects, and IMHO I found out there are minor differences.
Let’s compare the video output.

Systems used

Upper: original toastrack, lower: Harlequin issue 2D.

The perticular toastrack board on the upper photo had a bad keyboard membrane, hence I’m using the external mechanical (which makes it sound cooler) DK’Tronics keyboard 😉

The Harlequin board on the lower photo is inside some kind of toastrack case.

First test: the timing test I got from Dan

Upper: original toastrack, lower: Harlequin issue 2D.

There is a huge difference. No idea which one would be the correct one as both have some strange details.

Second test: NMI 3 demo – part 6 ‘Splitty Overscan’

I selected 128 timings when I ran this.
Upper: original toastrack, lower: Harlequin issue 2D.

It’s quite clear that the upper photo (from the original toastrack) runs as it should.

Third test: Vectron

Upper: original toastrack, lower: Harlequin issue 2D.

No noticable difference here.

 

Conclusions

IMHO there are timing differences.

I received this info about timings:
“Harlequin issue 2D has the same timing as toastrack,100%.
Toastrack use 17.7345MHz crystal, divide by 2.5 to get pixel clock = 7.0938MHz
Issue 2D use 28.375MHz crystal, divide by 4 to get pixel clock (HCa) = 7.09375MHz.”

But how I read that is that the first line contradicts what is said in the last 2 lines: there is a minor timing diffenerence.

It’s not a big deal

Even with slight differences in the timings, 99.9% of all games will run as they were developed without any problems.
Only some demos will show this deviation.

So I will continue with Issue 2D.
If there will be an updated revision with better timings that I can produce, I will.