CMD Board
The CMD board is the primary control board for the CDC Phoenix Drive. The CMD board uses the AM2900 series of chips along with microcode stored in a collection of ROMs, much like the CPU6 Board. In order to realize the level of chip density necessary to keep the CMD board contained to a single board, it uses a very complex Multiwire PCB design.
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Multiwrie construction is essentially an early method of achieving essentially an 8 layer board. The Multiwire board starts with an already complex 4-layer board, featuring a ground and power plane, then an upper and lower copper plane, and then adds an additional four layers of enameled wire held in place by epoxy. This enables an incredible amount of chip density to be achieved, which is how the CMD board can only be a single board as opposed to the DSK/AUT and DSKII Boards, which take up two full slots.
This did however come with some drawbacks. The Multiwire boards are incredibly fragile. Any flexing can cause the internal enameled wire to snap, essentially severing a trace. Not only does this cause failures or erratic behavior, the fault is incredibly difficult to trace down and troubleshoot, especially so without a full-fledged schematic for the CMD board.
At this moment, we do not know anything about the basic layout of the CMD board.
No schematics have been reverse engineered for this board at this time.
The CMD board contains 11 ROMs in total that make up the microcode for interfacing with the CDC Phoenix Drive. It should be noted that these ROM files look very suspect. It is highly likely that some or all of the ROM files are bad or corrupt in some way.
| Board | Location | Usage | IC | Link |
|---|---|---|---|---|
| CMD | A7 | Microcode | TBP18S030 | Link |
| CMD | B3 | Microcode | TBP28S86AN | Link |
| CMD | C3 | Microcode | TBP28S86AN | Link |
| CMD | D3 | Microcode | TBP28S86AN | Link |
| CMD | DC3 | Microcode | TBP28S86AN | Link |
| CMD | E3 | Microcode | TBP28S86AN | Link |
| CMD | ED3 | Microcode | TBP28S86AN | Link |
| CMD | F3 | Microcode | TBP28S86AN | Link |
| CMD | HF3 | Microcode | TBP28S86AN | Link |
| CMD | F12 | Microcode | 6309 | Link |
| CMD | H15 | Microcode | TBP18S030 | Link |