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Old 20 August 2018, 20:17   #1
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A4000TX ATX Amiga motherboard

Let me introduce to you the latest Amiga motherboard project I've been working on.

A4000TX ATX motherboard
, the first Amiga based motherboard in ATX form factor (actually a hybrid ATX/EATX form factor).
A4000TX is an A4000cr motherboard and daughterboard embedded together with a few additional features.
The motherboard is fully hand-routed like the A4000+ Alice motherboard was.

The specifications of the A4000TX Lisa rev 1.0:
- fits into (E)ATX case
- uses standard ATX power supply
- Amiga AGA custom chipset
- CPU slot connector for accelerator cards
- on-board 68030 CPU
- on-board 68882 FPU
- 16 MB Fast RAM
- 2 MB Chip RAM
- four full-length Zorro III slots
- three ISA slots
- extended video slot
- 3.5" IDE port
- internal floppy port
- PS/2 keyboard port supporting Amiga and PC keyboards (PC work in progress)
- PS/2 mouse port (work in progress)
- Amiga mouse and joystick ports
- serial and parallel ports
- 15-pin VGA port with 15kHz RGB output
- 24-pin breakout header with full RGB port support (for external scandoublers, genlocks, SCART cables, etc..)
- 3.5mm stereo jack
- on-board RTC with battery

Blank PCB

Here are pictures of the blank pcb.

The board is a four-layer PCB, which is quite crowded with components and traces both on the top and bottom side.
There is no space left on the board for many additional components.

Assembled PCB

Here are a few pictures of the assembled PCB.

Motherboard installed in an ATX case

The motherboard was installed in a standard ATX case.

Motherboard I/O connectors

Here is a picture of the back of the case showing the I/O connectors.

I/O connectors from top left to bottom right are
- PS/2 keyboard (Amiga or PC)
- PS/2 mouse (PC)
- Amiga mouse port
- Amiga joystick port
- serial port
- parallel port
- VGA port (15kHz RGB output)
- 3.5mm stereo jack

Behind the VGA port is the 24-pin breakout header to which you can plug in your custom-made cable (for scandoublers, genlocks, SCART, ...).

A4000TX motherboard dimensions

The picture below shows how much free space is required at the bottom of the case for fitting the motherboard.

The A4000TX motherboard is a hybrid ATX / EATX form factor board.
The standard ATX motherboard dimensions are 30.5cm x 24.4cm, EATX has 30.5cm x 33.0cm (height x width) (EATX = Extended ATX).

The aim was to create an Amiga motherboard that would fit to most ATX cases and still support full-length Zorro cards.
Top side of the motherboard has standard ATX dimensions (24.4 cm wide).
The bottom side had to be made wider (30 cm) so that full-length Zorro cards can be used with the motherboard.
The motherboard can be fitted into a standard ATX case if there is enough space at the bottom of the case. A full-length Zorro card is 34cm long.
Alternatively the motherboard can be fitted into an EATX case.

In the picture the motherboard was installed into an Enlight ATX case that takes standard size ATX motherboards only, no EATX.
And yet the motherboard fitted in well.

The motherboard is fully working (except the PC keyboard and PC mouse support that need fine tuning).

I have some prototype boards that I will be putting for sale soon if there is interest.

I would like to hear what you think, is there a demand for an ATX motherboard like this.
And also if there are some features missing that you would like to have in some later revision (reasonable please, can't embed a PPC there...).

All kind of discussion is welcome. Thanks.

Last edited by hese; 20 August 2018 at 20:22.
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