First, welcome!

Second.... getting parts from China is always more of an issue of getting something that works. In general, providing a schematic of your circuit would help, along with what it's connected to, etc. Second, any code you've written trying to get it working is helpful.

The one thing that stands out is your clock rate. older NOS Rockwell parts were typically rated at 1MHz. Trying to run them faster usually doesn't work. Unless you have a 2MHz spec'd part, you should drop the CPU clock down to 1MHz. A quiet power supply is also important, so you might want to try something as simple as a 7805 regulator with some decoupling caps and driven from a 9-volt supply.

Posting pictures of your breadboard layout can also be helpful. FInally, if you don't mind trying someone else's code, look at my Github page and download Micromon.... it's a very small monitor that will drive a 6551 as a console. If it doesn't work, you have a hardware problem. Hope this helps.

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Regards, KM
https://github.com/floobydust

I have some 6551s and 6551As a bought from the US (rather than China) 15 years ago if you're in Europe and need a replacement. The UK WDC supplier normally has authentic WDC W65C51s at a reasonable price.

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Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs

Welcome!

My first questions have to do with your oscilloscope probe. I hope you are using the X10 ("times ten") setting, as this results in the probe having much less capacitance (compared to X1) and thus less chance of the probe disturbing the circuit it's measuring. Also, it's important that your circuit's ground be attached to the ground lead on the end of the 'scope lead. IOW don't rely simply on an alternative connection that somehow attaches circuit ground to the scope itself.

A photograph would be helpful. That's because the actual routing of ground and power connections can make a difference with wonky problems like this!

-- Jeff

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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
https://laughtonelectronics.com/Arcana/ ... mmary.html