+++
title = "IMC-2001"
+++

# IMC-2001

This is an old Taiwanese Apple \]\[ / CP/M clone. 

# Status

Trying to fix several issues:
- power switch makes some hissing noises
- the lever moving the contacts between 40-character and 80-character
  mode for the CRT output is corroded, doesn't always make contact
  and produces a flickering image
- keyboard cable is broken, at least the data line
- the paddle and the joystick connectors miss some legs for putting them into
  the sockets on the motherboard
- sometimes I get into the monitor
- ~~lower-nibble bit 3 of the key
  being pressed is missing, unclear where it is lost, I suspect a
  bad register on the motherboard holding the current ASCII value of
  the key pressed or something similar~~. Replaced a bad 74LS257N,
  works now just fine.
- ROM 1 with BASIC is broken (and gets really hot). This explains
  the booting issues.. (will be tricky to get a replacement)
- possibly much more

Known things to work

- The keyboard works electronically (8039 MCS-48 like CPU with a 2K EPROM)
- the Rockwell R6502 CPU has a phase 0 clock and seems to go through
  address lines and output data (another strong indicator is the 'Apple \]\['
  sign on the monitor when switching on which indicates 6502, 40-character
  ROM, video circuit seems to be just fine).
- Monitor is working just fine (which is sort of amazing for such an old
  CRT monitor).
- I can boot from a Apple \]\[ CP/M 56k floppy and I get a prompt, now
  as the keyboard works and the CP/M on the 80-character card I can also
  assume the Z80 is working just fine.
  
# Images

From the outside:

{{< figure src="/images/hardware/imc-2001/computer_full.jpg" alt="IMC-2001" >}}

Booting into Apple \]\[ CP/M 56k:

{{< figure src="/images/hardware/imc-2001/cpm_40chars.jpg" alt="IMC-2001" >}}

The motherboard and floppy drives:

{{< figure src="/images/hardware/imc-2001/motherboard_internal.jpg" alt="IMC-2001" >}}

Keyboard layout:

{{< figure src="/images/hardware/imc-2001/keyboard_front.jpg" alt="keyboard layout" >}}

Keyboard has a 8039 CPU inside and a 2K EPROM:

{{< figure src="/images/hardware/imc-2001/keyboard_pcb_controller_prom.jpg" alt="PCB and controller" >}}

On the oscilloscope:

{{< figure src="/images/hardware/imc-2001/oscilloscope_serial_keyboard.jpg" alt="serial keyboard signal" >}}

Broken keyboard cable (the black pins are just connectors added by me to test connectivity,
both connector are female per default):

{{< figure src="/images/hardware/imc-2001/keyboard_cable.jpg" alt="PCB and controller" >}}

# Documentation

This is the "Operation Manual for IMC-2001, version 2.01":

{{< figure src="/images/hardware/imc-2001/manual_frontpage.jpg" alt="manual frontpage" >}}

[The complete scanned manual](/hardware/imc-2001/manual_imc_2001_2.01.pdf)

# Schematics

Power connector on the motherboard:

```
O O O O O O
| | | | | +--- GND   black
| | | | +----- +12V  red
| | | +------- -5V   blue
| | +--------- -12V  brown
| +----------- +5V   white
+------------- +5V   white
```

keyboard cable connectors:

connector to machine (sort of a gummy version of a DB-9):

computer has a 9-pin DSUB connector male:

```
  +-----------    white  INTR
  | +---------    black  GND
  | | +-------    green  DATA
  | | | +-----    blue   RESET
  | | | | +---    Yellow CLOCK
-------------
\ O O O O O /
 \ O O O O /
  ---------
   | | | +----    red    5V
   | | +------    n.c.
   | +--------    n.c.
   +----------    n.c.
```   

On the keyboard PCB there is a strange white connector with the following layout:

```
    +------------- white   INTR (active low, after last clock tick)
    | +----------- black   GND
    | | +--------- blue    RESET (active low)
    | | | +------- green   DATA
    | | | | +----- yellow  CLOCK
    | | | | | +--- red     +5V
   +-----------+
   |o o o o o o|
   +-----------+
   |           |
```

# Links

* [Mention of the IMC-2001](http://www.epocalc.net/php/liste_models.php?texte=&look=All+fields&yearmax=2018&nocomp=pc&cat=Apple+2+clone):
  mentions it on the list of Apple clones
* [Youtube video of similar machine](https://www.youtube.com/watch?v=c7crlJg80Zg):
  "APPLE II CLONE + CP/M ------- IMC 2001 made in taiwan.--------", Retro Computacion Argentina Jorge E. Nuviola