Zorro II expansion card which gives your Amiga the following:
2 x serial ports (DB9) up to 614400 baud.
1 x parallel port. (DB23)
1 x MIDI port.
1 expansion port
Additional details:
Rev 4
Prototype board never released (#011). A missing trace on the rear of the PCB layout (jumper trace present). Socketed PAL chip and clock.
Rev 6
First production board. All possible connectors, sockets, and potential components, no PCB layout mistakes.
Rev 7
Cost reduced. The MIDI option was deemed not to be unpopular, but the serial ports were very popular. Components which were not needed for the serial and parallel functions and therefore removed: J4, ROM socket, 10-pin MIDI header, and 37 0-Ohm jumpers in front of various connectors. The MIDI functions were still available in software if a 10-pin header was added and the optimal oscillator / driver tooltype setting present.
Previously Undocumented 'Reserved' Jumpers:
J3 - Hardware AutoConfig Disable (for testing/debug use only) - Shorted, the board will not AutoConfig, and any downstream boards are not sent the AutoConfig signal on the Zorro bus.
J4 - ROM Disable - If the U5 ROM socket was installed, any boot ROM (like a GVP FastROM) could be placed there to activate other boards at boot time. However, the GVP I/O extender never had a 'boot ROM'. The GVPIO driver/icon combo was put in the Expansion drawer, and activated with Binddrivers during startup.
J6 - Modified a parallel port signal between the PC and Amiga parallel port modes.
There were no other products made for the Option connector, though it contains most, if not all, of the important signals from the DPRC or serial/parallel port (pin out was never documented). Standoff holes were provided at the bottom of the card for a potential option card's stability.
Edit/Under Reconstruction: The early I/O Extender manual describes a MIDI option kit (external) which would have provided up to two 16x channel MIDI busses, with each bus providing 5x common 5-pin DIN MIDI connectors for IN, THRU, and 3x OUT. Research is ongoing (2024) as to the actual MIDI product kit design and options mentioned. The 9-pin D-sub MIDI connector seems to have not been documented well, either, but essentially had signals from the serial port(s) needed for an external unit. The 34-pin port also has some power feed pins for which an external MIDI unit may have wanted/needed if it was to be powered from the card. Seeking actual hardware or useful documentation if anyone has it in hand.
Field Observations:
- Rev 5/6 (PCB Silkscreen) is a fully functional board with MIDI 9/10-pin header and the (unused) ROM socket.
- Rev 6.01 (paper label) omits the ROM socket and the rearward MIDI 9/10-pin header.
Rumors of a network option were just that - rumors. At best, a PLIP-like Ethernet-over-serial communications solution with another node which might benefitted from the high baud rates possible could have been done. No plans existed to use an Ethernet chipset.
Manual Mistakes:
The GVP I/O Extender serial port, as included on the GVP A2000 G-Force '040 board, is numbered as serial port 0. When followed by a GVP I/O extender in a Zorro II slot, the first two ports on the first I/O Extender are numbered serial port 1 and 2, on the gvpser.device. The manual incorrectly states that port 1 in the sequence is skipped/not used. Subsequent I/O Extender serial ports on additional Zorro II cards would be numbered 3 & 4, 5 & 6, etc. Stacked parallel port interfaces would also increase in ther port numbering by 1.
Note: The GVP G-Force '040 board has the same kind of hardware (but a VL16C551 chip with only 1 serial port). The software knows there is no port or connector space for the missing port, and correctly skips the unconnected hardware. The board had the wiring for another port, but external no header space.
Picture note:
The Rev 4 card is a prototype that was never shipped. It is much like the Rev 6, but has a missing trace on the rear (jumper wire visible). This card has a 20Mhz oscillator, and is functional, but it does not adversely impact the serial/parallel performance. The oscillator was soldered in on production boards.
Any oscillator value is valid (for serial/parallel operations) up to the speed rating of the VLSI I/O chip on the PCB as long as the clock frequency value is updated in the Expansion drawer's driver Tooltype. A higher value, up to that limit, will make possible the higher baud rates particularly for sending, although it may still be limited by CPU response to clear pending interrupts to flush the bufers. This in turn can be more difficult for the CPU to service if mutiple channels are all running at higher inbound rates. The (default) 7.372800 clock value only matters to MIDI function/calculations, and this is the default oscillator on the G-Force 040 bord. All boards must have the same oscillator frequency, or irregular results may occur on some communications.
BOM details from internal GVP documents can be found here: https://archive.org/details/gvp-io-extender-bom