Z80,
Been developing and using the Z80 since I got my Northstar Z80 cpu
for Altair in early 1977 at that time a 4mhz part or easily twice the
8080 speed.
I have not less than...
5 Z80 s100 systems??
3 Z80 SBCs? (amproLB+ is still in regular use).
12 VT180 (two complete and 10 Z80 boards which
? ? ?are complete systems sans terminal).? The VT180
? ? ?was a VT100 terminal with a serial connection to a
? ? ?Z80 system floppy and IO complete and 64K of ram.
? ? ?The only shared thing was power supply, case and
? ? ?used the VT100 power on reset signal.
2 TRS80 (early)
And many SBCs of my design using Z80.
I also have a later set of systems based on Z180 (z80 with
integrated peripherals) and Z280 a really extended Z80
with 16 bit bus.
Its a versatile CPU that had dominated the 8bit world?
and the only other that had a significant presence was
the 6502 (AppleII and friends).? ?Both have demonstrated
extended life compared to many.? ?They are the two that
still appear the most besides 8085 and 1802.? Other well
knowns that seem to have disappeared are?6800, TI9900
(not the console but the CPU), Signetics 2650.? What
helped the Z80 stay alive was speed by '81 6mhz was
delivered and a year or two later 8mhz parts.? Now its
possible to find 10 and even 20mhz parts.
It had staying power because of speed,? instruction set and?
peripherals (and could use 8080/8085 supporting parts as well).
Its instruction set including all the 8080 have a large selection
of 16 bit and extended instructions with options for increment
or decrement and repeat.? My favorite is JP NZ,target (also
seen as DJNZ target).? There are three instruction mnemonic
sets in use, official Zilog, one I call Alternate-80 extended,
and TDL.? The latter two use the format most common to
8080/8085.
As to compatibility with 8080, there were a few programs that
behaved wrong on Z80 and that was early.? Later compatible
8080 code noted the small differences in flag use and avoided
those traps.? Smaller systems suffered that but it was both flag
and IO devices used that caused code uniqueness that made
code incompatible.? ?Most of the CP/M 80 applications was
compatible 8080 unless marked as Z80 required [used
extended instructions].? Generally 8080 was binary compatible
with Z80 but and only in carefully crafted cases the reverse
by avoiding the z80 unique instructions.
Comment to date I've not found any z80 that didn't have the
"unsupported instructions".? Same for the 8085 "hidden instructions".
By that point in time semiconductor makers understood the need
to be completely compatible as in identical.
Generally a CP/M user, either CP/M2.2 flavor or Zrdos.?
I have on S100? NorthStar? Horizons that run
NSdos a primitive tag and bag disk monitor but one
of the early mini-floppy (5.25") disk systems as part
of the main box.? There is also Uzi-Z80 a unix look alike.
Most of the other OSs are in the rare or platform unique l
ike TRSdos/Ldos and MSX.? There are a large set of real
time OSs for Z80 as well.
For me its 44 years of z80 and still running.
Allison
