A4000 fastram address error

[Tumbleweed]

I had an issue with Fastram not being recognised. I replaced Buster and it resolved the issue. Check around the SIMM sockets for corrossion. Battery damage can extend under the SIMM sockets and you dont see it until you remove them.

Try swapping the SIMMS around. Start with one in the first slot, then try it in the seocnd and so on for third and fourth and see what Diagrom reports after each run. May help you narrow it down if tis a problem with a SIMM socket.

Weed

[Tumbleweed]

Thats how I identifed the problem with Buster. I swapped it with a -07 version from my A3000D (the A4000 was -09); the -07 doesnt work properly in the A4000D but it did highlight the issue. I ordered a -11 part from Analogic. Price of Busters has since shot up - I got mine for I think less than £100, Analogic now selling them for c£150.

Chip Name          Part Number        Used in
Buster 5721           318075-01   A2000
Buster 5731 Rev A   318075-02   A2000
Super Buster 71           390529-06   A3000
Super Buster 45           390537-09   A4000
Super Buster 71           390539-07   A3000
Super Buster 45           390539-09   A3000, A2631
Super Buster 45           390539-11   A4000, A4000T

From Big Book of Amiga Hardware: https://bigbookofamigahardware.com/bboah/product.aspx?id=1484#:~:text=Though%20you%20think%20it%27s%20the%20same%20chip%2C%20there,it%20does%20NOT%20support%20Zorro%20III%20bus%20masters.

https://www.analogic.co.uk/shop/amiga/a4000/shop-amiga-a4000-chips-and-roms-html.html

Good luck.

Weed.