Tester Z80

The Z80 processor tester was created as a reaction to the discontinuation of the Z80 CPU production by Zilog and the subsequent increase in prices, which led to the proliferation of counterfeit processors.

The tester can detect whether the processor under test is NMOS or CMOS on the basis of power consumption, but also on the basis of the result of the OUT (C), 0 instruction. In the next steps, the tester attempts to discover the chip manufacturer based on the behavior of the CCF and SCF instructions when the undocumented flags F.5 and F.3 are set. Since different manufacturers deal with flag setting differently, some manufacturers can be detected.

All basic tests, which include the response to interrupts, are run at 2 MHz. In the last test, the tester tries to find out the maximum frequency at which the processor can still operate. The tester increases the frequency in steps, and after each change a number of instructions are tested and their effect on registers and flags is monitored.  If there are no errors, the CPU power consumption is measured and then the test is repeated at a higher frequency up to 33MHz.

The status of all tests is displayed on a small OLED display.

You can watch a video of testing my collection of CPUs on YouTube .

Ask for details.