Enhancing and modernising the A4000/040
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.
Below is an A4000 motherboard and A3640 with all the modifications applied. Click to view the full sized image.
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.
1:- Remove and replace leaking battery with CR2032 lithium.
2:- Upgrade motherboard RAM to 64MB.
3:- Upgrade Kickstart ROM size to 1MB (machine translated from French).
4:- Upgrade Kickstart to version 3.9, add custom modules.
5:- Upgrade AT-IDE interface from mode 0 to mode 2.
5:- 68030 state machine mod - improve motherboard RAM access speed when using A3640.
6:- Improve ability to overclock the A3640.
7:- Upgrade 68040 to 68060.
8:- Add threaded spacers to support CPU card.Helps ensure the CPU card is firmly attached.
9:- Add headers for cooling fans. A pair of two pin headers can be soldered into existing holes next to power socket, providing 12V.
10:- 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.
11:- 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.
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Introduced 25th April 2015. Updated 25th April 2015. Version 1.0