IMPORTANT INFORMATION. It is highly recommended you read this entire page before assembling the Amiga 2000 EATX.
Disclaimer: This project is free and open source. It is a complex project and should only be undertaken by individuals experienced in SMD assembly techniques. No warranty or guarantee is offered that it will work for your particular situation. You assume all risk should you choose to build it.
This Amiga EATX PCB makes use of many modern surface mount components. These and the other standard components are available from most any good electronics supply house. In addition, you will need to obtain the legacy components shown in Table A1.
Notes:
- If you do not intend to use a bridgeboard or the ISA slots, you do not need to install the components shown in the ISA SUBSYSTEM silk screen.
- When space was available, the values of components are listed on the PCB. In the event several components are placed together with the same value, the value may be shown once and the components will be marked together on the silk screen.
- All end-of-life (no longer manufactured) components for this project are listed in table A1.
- Always verify the orientation and location of all IC's before attaching. Never assume the orientation matches the original A2000.
The best source of parts for this project is a dead or dying Amiga 2000 board. Otherwise, many of the Amiga legacy IC's and parts can be obatined from various internet suppliers. Unfortunately, Buster (MOS 5721) can be difficult to find. Beware the original Buster revision (318075-01) has a buffering error and cannot be used without a "Buster Tower". Be sure to use the one specifically listed in Table A1 or build a replacement option.
You will need an oscillator installed at X1 or X2 to generate a clock signal. You can find 5V TTL oscillators from various legacy suppliers in the 14-DIP format. In the event you cannot find one, you can use a 3.3V CMOS oscillator of the same frequency in position X2. See Table A1. Do not populate both X1 and X2.
Note on China sourced oscillators: There are reports that some new 14-DIP oscillators sourced from China have an output enable signal on pin 1. Original 14-DIP oscillators have no connection on pin 1, thus pin 1 of X1 is not connected on the Amiga 2000 EATX board. If you have one of these oscillators and are not getting oscillations, or random system halts/crashes, you can try pulling pin 1 to logic high by temporarily bodging a resistor (<= 10k ohm) to pin 14 of X1. If that corrects the issue, you can make the bodge permanent.
Note on X2 CMOS oscillator: 3.3v CMOS logic is compatible with in-spec TTL logic. My test board worked well with a +3.3V CMOS oscillator. All clock signals from Agnus are correct on my test machine. I would still recommend using like-for-like logic, if possible. Using the +3.3V CMOS oscillator should only be considered if a TTL oscillator cannot be reasonably obtained.
The revision 2.x board supports multiple Agnus revisions. See Table A2 for a list of part numbers supported. Not all the listed part numbers have been directly tested. Reviewing related literature suggests all the listed parts numbers should work. However, until each specific part number is tested, there is no guarantee any particular Agnus will work, even if listed. Table A2 indicates the status of each part number. If you test a new Agnus part number, please place a new post in the issues tab so the table can be updated.
The Agnus solder pad jumpers are not configured from the factory. During board assembly, the jumpers defined in Table A3 must be configured for the specific Agnus part number to be used. The individual assembling the board must correctly short each jumper, as necessary. Failure to correctly do so will result in a malfunctioning board. Most of the configuration jumpers are on the back of the board, with only JA13 on the front of the board. See Images 1 and 2. The jumper pad locations are circled in red.
Image 1. Agnus Jumper Locations - Front
Image 2. Agnus Jumper Locations - Back
Due to lack of availability of +5V SRAM, the revision 3.0 board was set up for +3.3V SRAM. All other board revisions, including 3.1, come from the factory set up for +5V SRAM. The revision 3.x boards include jumper J503, which is used to set the SRAM voltage. It is important to note the voltage of your SRAM part and set J503 accordingly. It is recommended to use the +5V part on all revisions.
The Amiga 2000 EATX (revision 2.2+) can support an externally or internally generated TICK. The factory default configuration for J300 is to short pins 1 and 2, which uses the _VSYNC signal from Agnus as the time base signal. For most configurations, the factory default is acceptable. However, if you intend to use video devices that replace the system clock via the _XCLKEN and XCLK signals, you should supply an external time base (TICK) signal. These types of video devices include genlocks, flicker fixers, and possibly others. See your product manual to determine whether this is of concern. Two accurate external TICK generators are included with this project and can be found in the TICK folder. These devices are small boards with simple circuits intended to be installed directly on J300. For details on J300, see table A6.
NOTE: You MUST jump pins 1 and 2 or install a TICK generator on J300 or your Amiga 2000 EATX will not function.
Revision 2.1 and earlier does not have a TICK header. In the event you need to add a TICK signal to an earlier revision, instructions for modifying revisions 2.1 and 1.2.1 can be seen here. If power is needed, +5V can be drawn from pin 20 and ground from pin 1 of U300. You may also tap C300, if that is easier. It is recommended you make this modification only if it is required by your video hardware configuration.
The Amiga 2000 EATX is provisioned to accept 512k (27C400, 40 pin), 1MB (27C800, 42 pin), and 2MB (27C160, 42 pin) Kickstart EPROMs. The Kickstart socket (U500) is a 42 pin DIP footprint that supports all three types. A standard Amiga Kickstart ROM is based on the 27C400 EPROM. When installing a 27C400 EPROM, you must install it toward the bottom of the socket, leaving pins 1 and 42 of the socket empty. This is noted on the silk screen and will correctly align the pins. Installing the 27C400 EPROM incorrectly may damage it! Install 27C800 and 27C160 EPROMs as normal. Use of 1MB and larger EPROMs is considered experimental. Guides to create custom Kickstart ROMs can be found on Amiga community sites.
CN303 is a 34 pin header that is reponsible for the internal floppy drives DF0 and DF1. Pin 3 is a key. That is, factory Amiga floppy drive cables often have a pin socket blocked to ensure the cable is oriented correctly before installing. As such, it is recommended you remove pin 3 from the header before installing on the board. You can often pull it out with needle nose pliers. Alternatively, you can cut it off with a wire cutter.
CN304 is a 20 pin header that is reponsible for external floppy drives DF2 and DF3. This header provides 12V on pin 18. Installing the cable backwards may result in damage to connected devices! Thus, the BOM includes a keyed, shrouded connector that will help prevent incorrect installation when used with a keyed cable. To use external drives, an adapter cable will need to be created. See Tables A4 and A5.
There are two options for the real time clock (RTC). You can install the original Amiga RTC circuit based on the MSM6242 or a simpler circuit based on the RTC-62423A. The MSM6242 based circuit requires tuning of the trimmer cap to dial in the correct timing. The RTC-62423A circuit does not require tuning. This sacrifices accuracy, in that the RTC-62423A may drift over time. It is up to the user to decide which option is more appropriate for their needs.
When installing the MSM6242 circuit, include components Y800, C810, and VC800. When installing the RTC-62423A circuit, Y800, C810, and VC800 are omitted.
The individual line items of non-legacy components with Digi-Key and manufacturer part numbers can be found here. This file can be used as a reference for ordering. This CSV file can be uploaded into your Digi-Key cart, automatically adding the required items to your cart. It will also tell you when bumping the quantity to the next price break will save you money. Quite nice! Note that some items are optional, depending on your desired configuration.
Each individual component and PCB reference can be found here. This is a useful reference for placing parts, especially for those locations where labeling the component value was not possible.
In addition to the items in the BOM, you will need to obtain the legacy components shown in Table A1. Select a single oscillator that matches the video standard you desire.
You should download the interactive BOM, which will help you locate components on the board. It can be found here. Download the file and open it in your browser.
There are a few single diodes on the board. They are designated Dxxx and marked with a rectangle with one open side. The closed side indicates the cathode. This is often marked on the diode body with a solid line.
The electrolytic caps on the board are polarized and must be installed correctly. Electrolytic caps have a black mark that indicates negative (-). Positive (+) is marked on the board. Align the black side away from the + mark. Ceramic capacitors are not polarized and may be installed in either direction
Pin 1 of surface mount ICs may be marked in a number of different ways. A small circle, notch, line, or text alignment can indicate pin 1. If in doubt, check the data sheet. A small circle marking pin 1 has been placed next to each surace mount IC on the board to assist with orentation. There are also lines drawn across the top and bottom of the SMD position. The longer line indicates pin 1.
Throught hole IC's have a square pad and a "1" marking pin one. Pin one is usually indicated with a small notch on one end of the IC body. Occasionally, there may be a small circle on the IC body indicating pin 1.
Solder pad jumpers are present on the board. In the event there are only two pads for the jumper, you will place a solder blob across the two pads to short them when necessary. In the event of a 3 pad jumper, the solder blob must be placed between pad 2 (the center pad) and either pad 1 or 3, as defined in Table A3. Pad 1 is marked with a small arrow and the numeral "1" on the silkscreen. Pad 3 is marked by a number "3" on the silkscreen.
| Common Name | Designation/Part Number | Postion | Package | Notes |
|---|---|---|---|---|
| Motorola 68000 | MC68000 | U100 | DIP-64 | 8MHz or greater |
| Fatter Agnus | See Table A2 | U101 | PLCC-84 | |
| Gary | MOS 5719 | U102 | DIP-48 | |
| Paula | MOS 8364 | U200 | DIP-48 | |
| Denise | MOS 8362 or CSG 8373 | U201 | DIP-48 | Deniser |
| CIA | MOS 8520A, 8520A-1, 8520R2, or 8520PD | U300 and U301 | DIP-40 | These are all interchangeable |
| Buster | MOS 5721/318075-02 | U800 | DIP-48 | Bluster |
| Kickstart | Commodore ROM or Burned 27C400/V1.2+ | U500 | DIP-40 | Various Amiga suppliers sell ROMs ready to use |
| Video Hybrid | Commodore 390229-0x | HY200 | SIP-22 | Video Hybrid |
| Real Time Clock | RTC-62423A | U801 | SOP-24 | "A" revision is more accurate, but non-A version can be used |
| Optional Real Time Clock | MSM6242 | U899 | DIP-18 | This is the original, tunable RTC from the Amiga |
| 28.636363 MHz Oscillator | NTSC Oscillator, 5V TTL | X1 | DIP-14 | Alternatively, populate X2 with a 5.0x3.2mm footprint 3.3V CMOS oscillator |
| 28.37516 MHz Oscillator | PAL Oscillator, 5V TTL | X1 | DIP-14 | Alternatively, populate X2 with a 5.0x3.2mm footprint 3.3V CMOS oscillator |
*Commodore IC's may be marked "MOS" or "CSG", or possibly neither in the case of contract runs. These are interchangeable by part number.
| Agnus | Commodore Part Number | Status |
|---|---|---|
| 8372A | ALL | Tested and working |
| 8375 | 390544-01 | Tested and working |
| 8375 | 390544-02 | Tested and working |
| 8375 | 318069-10 | Tested and working |
| 8375 | 318069-11 | Tested and working |
| 8375 | 390554-01 | Unknown |
| 8375 | 390554-02 | Unknown |
| 8375 | 318069-12 | Unknown |
| 8375 | 318069-13 | Unknown |
| Agnus | 8372A | 8375 | 8375 |
|---|---|---|---|
| Commodore Part Number |
ALL | 390544-01 390544-02 390554-01 390554-02 318069-12 318069-13 |
318069-10 318069-11 |
| Jumper | |||
| JA1 | 3-2 | 1-2 | 1-2 |
| JA2 | 3-2 | 1-2 | 1-2 |
| JA3 | 3-2 | 1-2 | 1-2 |
| JA4 | 3-2 | 1-2 | 1-2 |
| JA5 | 3-2 | OPEN | 1-2 |
| JA6 | 3-2 | 1-2 | 1-2 |
| JA7 | SHORT | OPEN | OPEN |
| JA8 | 3-2 | 1-2 | 1-2 |
| JA9 | 3-2 | 1-2 | 1-2 |
| JA10 | 3-2 | 1-2 | 1-2 |
| JA11 | 3-2 | 1-2 | 1-2 |
| JA12 | 3-2 | 1-2 | 1-2 |
| JA13 | 3-2 | 1-2 | 1-2 |
| JA14 | 3-2 | 1-2 | 1-2 |
| J102 | SHORT for NTSC OPEN for PAL |
SHORT | SHORT |
1-2 = Short pads 1 and 2 together
3-2 = Short pads 3 and 2 together
SHORT = Short the two pads together
OPEN = Nothing is shorted
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | _RDY | 11 | DIR |
| 2 | _SIDE | 12 | _MTRX |
| 3 | _DKRD | 13 | _SEL3 |
| 4 | _WPROT | 14 | _SEL2 |
| 5 | GROUND | 15 | _DKRST |
| 6 | _TRK0 | 16 | _INDEX |
| 7 | GROUND | 17 | _CHNG |
| 8 | _DKWEB | 18 | +12V |
| 9 | _DKWDB | 19 | +5V |
| 10 | _STEP | 20 | GROUND |
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | _RDY | 13 | _SIDE |
| 2 | _DKRD | 14 | _WPROT |
| 3 | GROUND | 15 | _TRK0 |
| 4 | GROUND | 16 | _DKWEB |
| 5 | GROUND | 17 | _DKWDB |
| 6 | GROUND | 18 | _STEP |
| 7 | GROUND | 19 | DIR |
| 8 | _MTRX | 20 | NC |
| 9 | _SEL3 | 21 | _SEL2 |
| 10 | _DKRST | 22 | _INDEX |
| 11 | _CHNG | 23 | +12V |
| 12 | +5V |
| Pin | Signal |
|---|---|
| 1 | _VSYNC |
| 2 | Time Base (TICK) |
| 3 | GROUND |
| 4 | _RESET |
| 5 | NC |
| 6 | +5V |