My "Apple ][" "Europlus"

My father bought us an "Apple ][", somewhere around 1980. A friend of his was involved with importing Apple clones from Taiwan.

It's a Taiwanese UNITRON, not to be confused with the Brazilian Unitron.

We started off without floppy drives -- I wrote a "breakout" lookalike in Integer Basic, which I eventually lost when the cassette I was using failed.

Later we got floppies, as well as a Z80 softcard and 80 column card for running CP/M.

I spent many many hours on this machine, coding, playing games, hacking games to give more lives, trying to break copy protected disks, and the like. Remember Zardax? It was an "upcopyable" word processor, apparently quite good by 1984 standards. I made the best copy I could, then spent hours trying to figure out why it didn't boot. Never managed to make it work, though...

I managed to scrounge a ROM card, a complete set of Apple ROMs, and a pukka Apple motherboard (unpopulated). I used the ROM card to crack games, both copy protection and nifty things like getting extra lives and axes in Conan. I still have all my notes, someday I might post it...

September 2011:

Got my Apple up and running again. Had a dud RAM chip in the first bank. Found it with a logic probe -- D6 on the 6502 was not toggling while the rest of the data lines were, traced this through the buffers, keyboard MUX and latches to the RAM.

My RAM is a motley collection of chips from all over. This one time, the motherboard fried, and they replaced half the chips, including about half the RAM. Also, some RAM chips blew before, and I replaced it with what I could find.

So this time, I found my stash of 25 brand new 4164 64k x 1 chips. These have four times the capacity of the 4116 chips used in the Apple, and are 5V only parts (the 4116 needs -5V and +12V as well). Replacing 4116 RAM with 4164, 41256, etc_.txt.

From: "Matt Osborn" 
Subject: TECH: Replacing 4116  RAM with 4164, 41256, etc.
Date: Monday, October 23, 2000 12:40 AM

I saw some posts recently about replacing 4116 RAM with 4164,
which is more reliable (it uses only one voltage, not three!) and
is cheaper (if you know where to look!).  I wanted to come up
with a solution that works for all boards (no board hacking or
harness tricks involved).  So here it is:

Take your 4164 chip and bend pin 8 up and over the top of
the chip.  Solder a small wire from that pin to pin 9 (which
is directly across from it, and has +5V on it).  Pin 1 of the
4164 is not used... just snip it off so you don't have to worry
about the -5V on the board.  That's it.  The chip is ready
to plug into the socket of the 4116.

You can do almost the same thing with a 41256 (also known
as TMS4256, MCM6256, HM51256, MB81256, etc., 256k*1).
In addition to flipping up pin 8 and connecting it to pin 9,
bend up pin 1 and connect it to pin 16 (that'll tie the high
address line to ground... you can't leave it floating).

I used TMS4256 to replace some blown out 4116 in my
Juno First, and it works great.  Runs much cooler!!!
Soldering the wires is a little bit of work, but worth the effort.


This works well, and I replaced the first two banks, giving me a "160k Apple(!)" (of which I can of course only use 64k :-) Will upgrade the third bank sometime as well.

September 2019:

A bunch of keys are not working. Not matrix related, all over the show.

This is the UNITRON keyboard PCB after I removed all the keyswitches -- quite unlike the Apple equivalent. Instead of the AY-5-3600 keyboard encoder, it uses a handfull of TTL and a 2732 EPROM.

The interesting thing about this keyboard is that it also has a lower-case mode, sort of. Even though the motherboard does not support lower case. At the lower left, where an Apple ][ has the power light, the Unitron keyboard has a button / light combination.

Super Serial Card

Bought one off eBay. The jumper block has three broken pins.

Apple II Super Serial Card jumper block wiring and connections (jumper block pin 1
matching socket pin 1, "modem")

   1489 pin 3  CTS    1-+ +-16    DB25 pin 8  DCD
                        | |
   DB25 pin 5  CTS    2-+ +-15    1489 pin 4  DCD (via SW1)

   1488 pin 6  RTS    3-+ +-14    DB25 pin 8  DCD
                        | |
   DB25 pin 4  RTS    4-+ +-13    1489 pin 4  DCD (via SW1)

   1489 pin 10 RxD    5-----12    DB25 pin 3  RxD

   DB25 pin 2  TxD    6-----11    1488 pin 8  TxD

   1489 pin 13 DSR    7-----10    DB25 pin 6  DSR

   DB25 pin 20 DTR    8-----9     1488 pin 11 DTR

(This is in the Super Serial Card Installation and Operating Manual, on the schematic page.

Apple II Communications Card


Disk drives and controllers

Apple disk drives, controllers, and the IWM.

There are many badly-scanned schematics for the analog board inside the Disk II. You will find a decent schematic here or in the DOS 3.2 Instruction and Reference Manual on Rich Cini's page -- note that this is the one with R28 = 9k1, other analog boards have R21 = 8k2 in series with a 10k pot R33 "Pulse Width Duration".

More schematics.

Stellation Two The Mill

Somewhere along the way I acquired a The Mill 6809 co-processor. This is not the only 6809 co-processor for the Apple II, there was also the Seikou EXCEL-9, IBS AP-10 and maybe others.


I bought a Catweasel back in 2005. As of 2015 it's still unused.


I found some Wildcard PCBs on eBay.

Commsoft Photocaster

This is some kind of an SSTV system which sends black and white or colour (by scanning the same picture three times with different filters) pictures at a whopping 128 x 128 over a radio link. This cost $500 back in 1983, excluding the actual video camera. See this press release on page 98 of Ham Radio Magazine.

The board I have is a clone (here's the real thing). I doubt they would have sold a whole lot of them, but at $500 they would have been worth cloning!

80 Column Card

This is of course a clone of the Videx Videoterm, you can see they sat down with a Videx PCB and copied the traces by hand. And then they added some mods, look under the code EPROM. (The Videx used a 2708, the clone a 2716).

But more interesting, compare the traces to the Unitron 80 Column Card on AppleLogic. It's clear that that card is a direct (as in, same artwork) descendant of this one. So this might be a first-gen Unitron, before they got their act together? Or, KAM copied the Videx, and Unitron copied KAM? (The Unitron combines the two 2716 character generators into one 2732).

While the Unitron code EPROM is quite unlike the Videx EPROM 2.4 which is online in a number of places, there are only a few differences between my EPROM and the Unitron one.

KAM                                                                 Unitron

C800                 LDA     $6B8,X                                 C800                 LDA     $6B8,X
C803                 AND     #$F8                                   C803                 AND     #$F8
C805                 CMP     #$30 ; '0'                             C805                 JMP     $CA0B
C807                 BEQ     $C847 ; This is just an RTS            C808                 .BYTE $EA
C809                 LDA     #$30 ; '0'                             C809                 LDA     #$30 ; '0'
C80B                 STA     $6B8,X                                 C80B                 STA     $6B8,X

C883                 $7B $50 $62 $19 $14                            $7B $50 $5E $1F $19
C888                 $08 $12 $13 $00 $0B $C0 $0B $00                $20 $12 $16 $00 $0B $C0 $0B $00
C890                 $00 $00 $00 $7B $50 $62 $19 $1B                $00 $00 $00 $7B $50 $5E $1F $22
C898                 $08 $18 $19 $00 $08 $C0 $08 $00                $60 $18 $1D $00 $08 $C0 $08 $00
C8A0                 $00 $00 $00                                    $00 $00 $00

CA00                 BIT     $FFCB                                  CA00                 LDY     #$63 ; 'c'
CA03                 BVS     $CA09                                  CA02                 STY     $63B
CA05                 SEC                                            CA05                 LDY     #$73 ; 's'
CA06                 BCC     $CA20                                  CA07                 STY     $63C
CA08                 CLV                                            CA0A                 RTS
CA09                 STA     $CFFF                                  CA0B                 STA     $C059
CA0C                 JSR     $CB15                                  CA0E                 CMP     #$30 ; '0'
CA0F                 RTS                                            CA10                 BEQ     $CA0A ; RTS
CA10                 STA     ($28),Y                                CA12                 JMP     $C809
CA12                 SEC                               
CA13                 BCS     $CA05

So the Unitron code jumps to a patch at $CA0B which tickles AN0 at $C059 -- so it supports the soft video switch.

Also, the CRTC tables (there are two of them, 16 bytes each) are different -- Maybe PAL vs NTSC timing?

(Oh BTW if you're here because the code makes no sense and you're trying to figure it out -- The hardware maps the $CB00-$CBFF block to $Cx00, so PR#3 or IN#3 calls $CB00 not $C800. But that doesn't explain why my ROM has a copy of the $CB00 code at $CA00.

Basically this code makes no sense to me at this stage. The same flags get set and cleared over and over again.

C800 2C CB FF LC800  BIT     $CBFF  ; Set V. The 6502 has a SEC and CLC but no SEV only CLV.
                                    ; I would have used something from my own ROM, not from
                                    ; the Apple monitor. Maybe this came from someone's hints
                                    ; & tips. Or maybe they are looking for a different ROM,
                                    ; this will for example fail on the Apple III which has
                                    ; $86 where Apple ][ original and autostart and //e has $60
C803 70 04    LC803  BVS     LC809
C805 38              SEC
C806 90 (18)         BCC     LC820  ; save one byte by using the next instruction as a branch offset.
C807 18       LC807  CLC            ; Output is hooked here
C808 B8              CLV
C809 8D FF CF        BIT     $CFFF  ; Unmap ROM
C80C 20 15 CB        JSR     $CB15
C80F 60              RTS
C810 91 28           STA     (MON_BASL),X ; Input is hooked here
C812 38              SEC
C813 B0 F0           BCS     LC805  

Z-80 Softcard

Not much to see, just a Unitron clone of the Microsoft Z-80 Softcard




Copy Protection

The Apple ][ has some insane copy protection schemes. Follow 4AM to learn.


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