That is just not true. I now have a 200MHz scope and have being doing some measurements... some results below.eslapion wrote: ↑Sat Jun 10, 2017 8:33 amEven if J-PLA has the very exact timing of a genuine Commodore PLA, its outputs has a slew rate that's off the charts when compared to the real thing and this makes it a massive noise generator.
Only the 10ns version of the XC9536XL with its slew rate limiter enabled offers signals that are similar in nature to antique NMOS and TTL signals. You look at that on a good scope and you can't see the difference from a vintage 74LS series chip.
Here I have measured !CHAROM -signal (all signals are pretty same, doesn't matter which I selected).
These measurements have been made on a real 250466 mainboard using a 150MHz probe with 10x setting on and a very short
spring-type ground contact.
I pasted the images on top of each other, so that it's easier to see differences (which doesn't exist!).
I do find it a bit suprising that your 10ns chip and my 5ns, both genuine, have so similar results, there is hardly any
noticeable differences in slew rates.
As you (and everyone else) can see, there is no ringing on J-PLA either.
Slew rates on both PLAnkton and J-PLA are faster than any original PLA, but I don't find that problem at all.
If that slew rate makes J-PLA a "massive noise generator", then yours is like that too.
I wonder if that 5ns chip you have been measuring had "slow slew rate" and "low power" -modes activated?
And was it a genuine chip? You have been telling that counterfeits don't have working slew rate control, so did you
actually measure a fake chip and now your "facts" are based on that?