article from Dave's Amiga Hardware Page
Although the A4000 was the ultimate 'Big Box' Amiga, due to it's age and certain design compromises, there are quite a few performance limitations. These include slow motherboard RAM access (when using the A3640), slow AT-IDE interface and small motherboard RAM capacity. The modifications described here are intended to alleviate these, while also providing a worthwhile performance boost at reasonable cost.
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| A4000 motherboard and A3640 with all the modifications applied |
The Modifications
Below is a list of the modifications. You can do them all together or individually if desired. Most of these link to third party sites or forum discussions. - Remove and replace leaking battery with CR2032 lithium.
- Upgrade motherboard RAM to 64MB.
- Upgrade Kickstart ROM size to 1MB (machine translated from French).
- Upgrade Kickstart to version 3.9, add custom modules.
- Upgrade AT-IDE interface from mode 0 to mode 2.
- 68030 state machine mod - improve motherboard RAM access speed when using A3640.
- Improve ability to overclock the A3640.
- Upgrade 68040 to 68060.
- Add threaded spacers to support CPU card.Helps ensure the CPU card is firmly attached.
- Add headers for cooling fans. A pair of two pin headers can be soldered into existing holes next to power socket, providing 12V.
- Add header for reset button. This is soldered to pins 2 & 3 on the battery backed clock chip, and pulls /Fail to ground, resetting the Amiga.
- Replace capacitors on A3640. Note I used low profile 'chip' capacitors to allow clearance for 040/060 adaptor. Capacitors on the A4000 motherboard should be checked too.
First Published: April 25th 2015
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