A4000 IDE - searching for implementation details.

[pandy71]

As in title - looking for A4000 IDE implementation details - software and hardware.Seem A4000 IDE is implemented without custom IC, only trough simple PAL - will be interesting to reimplement such IDE interface on other than A4000 HW and use software from A4000 (ide/scsi device with possibility to update kickrom image).TIA.

[jasonsbeer]

Its very similar to the Gayle implementation, which is somewhat documented. If the ROM detects a Fat Gary, it assumes a hard drive controller is present. In the A3000, its SCSI. In the A4000, its ATA. Fat Gary will decode the hard drive address space and assert the SCSI enable signal, which goes to the PAL you mention. From there on, it should behave very much like a Gayle implementation.

The A4000 service addendum probably has everything you need to know. See attached image. There is more relevant info there.

I implemented the Gayle ATA with some help from LIV2 in an earlier version of the N2630. You can see the code here... https://github.com/jasonsbeer/Amiga-...-1.1.1/IDE.vhd

I don't think there's anything special about the A4000 ATA compared to the A1200/A600 ATA implementation with Gayle.

EDIT: Looks like I already have a PDF of the relevant ATA section of the A4000 Service Addendum. https://github.com/jasonsbeer/Amiga-...DE%20Specs.pdf

[pandy71]

Thx Jason - seem that scsi.device recognize Gayle presence and if Gayle is not present then scsi.device is inactive - i had perhaps naive expectation that A4k IDE is bit different, just few registers (virtual as they are located on HDD) at the particular address and that's all - using original scsi.device from A4k remove many issues related to Gayle detection.
Goal is to not sue programmable logic, just discrete ones so removing problematic programming part (unless you have detailed specification for AMD PALCE - seem to be unobtainum despite being 30 years old).