reZet80: Z80 NMOS/CMOS Test

Since 2016 when I started reZet80 I have accumulated about forty Z80 CPUs.
Most of them are standard Z80s in a DIP-40 package from ebay or unsoldered from old computers.
I also collected some exotic ones like the T6C79 from Toshiba and the ATJ3310 and ATJ3315 from Actions.
But I'll stick to the pure Z80 as produced by Zilog here.

A short history of Z80 CPUs:

Z80: 2.5 MHz NMOS

Z80A: 4 MHz NMOS

Z80B: 6 MHz NMOS

Z80H: 8 MHz NMOS

Z80: 4-20 MHz CMOS

I'll talk about the CPU speed in one of my next posts.

A simple 8-byte program will help me differentiate between NMOS and CMOS Z80 CPUs:
;=============================================================================
; take it easy
nop
; disable interrupts
di
; SENTINEL configuration register
ld c, 00h
; out (c), 0
db EDh, 71h
; loop forever
_loop:
jr _loop
;=============================================================================
NMOS CPUs output 00 (hex) executing the undocumented instruction "out (c), 0".
CMOS CPUs output FF (hex).
The SENTINEL configuration register is a 74HC273 latch.
I simply connect eight LEDs to the latch output to display the results:

Zilog Z80A (7725 date) ceramic package, clearly NMOS

Mostek MK3880 (7807 date) ceramic package, NMOS

Mostek MK3880 (8029 date) ceramic package, NMOS

SGS Z8400AD1 (18214 marking) ceramic package, NMOS

Toshiba TMPZ84C00P (8532 date) CMOS, extracted from a YAMAHA FB-01 mainboard.
I bought the FM sound generator from ebay so I can't comment on its history but I expected the CPU to be a genuine Toshiba CMOS part.

SGS Z8400B1 (88207 marking) NMOS as expected

Zilog Z84C0020PEC (0047 date) Bought from a leading ebay seller in China many years ago.
At least it seems to be a CMOS CPU, not a counterfeit NMOS one as expected.