IDE68K addressing

Yulquen74 · 16 May 2015, 12:14

Exactly what address range does those IDE expansions/Gayle emulators
for A500 occupy?

And are they implemented with address mirroring downwards?

I'm asking because I suspect potential conflict with FASTRAM in the
ranger area (0xC00000 - 0xDBFFFF).

Thanks in advance for any help.

Toni Wilen · 16 May 2015, 14:53

I don't know about about IDE68K but afaik only guaranteed safe "slow ram" region is 0xc00000-0xd7ffff (1.5M). Anything higher may hit some Gayle/other weird expansions.

Vot · 16 May 2015, 16:20

Is this what you were asking ?

It is necessary to connect two signals from the adapter board to the Amiga mainboard to get it to emulate A600's Gayle IDE behavior. One is /INT2 interrupt request signal, and the other one is /OVR, which is used here in an "unsupported" way: to disable address decoding by Gary, when address range $DExxxx is accessed. In A500 this is a mirror of the custom chip set addresses, but in A600 it is for special functions in Gayle, e.g. to detect presence of the IDE-interface of the Amiga 600. /OVR and /INT2 signals can be found next to each other at the 86-pin expansion connector. /INT2 can also be found at pin 21 of U7 8520 CIA (ODD CIA "A") in the Amiga 500, and /OVR at pin 29 of U5 Gary. /int6 is at pin 21 of the EVEN CIA "B", U8 in A500.
/OVR and /INT2 are available on the top side of the 86-position card-edge. Number one is a ground contact, and so is the next one beside it. In older A500 mainboards (rev5) these two positions may form a big unified copper area. When counting the top side positions, /OVR is the 9th, and /INT2 the 10th. In "pin-numbers": /ovr = pin 17, /int2 = pin 19, /int6 = pin 22. Link "Google" for other finds of information.

Yulquen74 · 16 May 2015, 16:39

Hi,

Toni really answered my question.

The case is in regard to my FAST-RAM board for A500 which enables the usage of
the entire 1,7MB slowfast area in addition to its other memory areas, totaling 12,6MB.

My goal was to make it compatible with the IDE68K board (and similar).

I have now just made the last 256KB of this area (0xD80000-0xDBFFFF)
optional by the means of one of the available switches on the board, so it should now
be possible to install in a machine with the IDE68K.

16 May 2015, 12:14	#1
Yulquen74 Registered User Join Date: May 2013 Location: Kleppe / Norway Posts: 258	IDE68K addressing Exactly what address range does those IDE expansions/Gayle emulators for A500 occupy? And are they implemented with address mirroring downwards? I'm asking because I suspect potential conflict with FASTRAM in the ranger area (0xC00000 - 0xDBFFFF). Thanks in advance for any help.

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16 May 2015, 14:53	#2
Toni Wilen WinUAE developer Join Date: Aug 2001 Location: Hämeenlinna/Finland Age: 49 Posts: 26,534	I don't know about about IDE68K but afaik only guaranteed safe "slow ram" region is 0xc00000-0xd7ffff (1.5M). Anything higher may hit some Gayle/other weird expansions.

16 May 2015, 16:20	#3
Vot Registered User Join Date: Aug 2012 Location: Australia Posts: 651	Is this what you were asking ? It is necessary to connect two signals from the adapter board to the Amiga mainboard to get it to emulate A600's Gayle IDE behavior. One is /INT2 interrupt request signal, and the other one is /OVR, which is used here in an "unsupported" way: to disable address decoding by Gary, when address range $DExxxx is accessed. In A500 this is a mirror of the custom chip set addresses, but in A600 it is for special functions in Gayle, e.g. to detect presence of the IDE-interface of the Amiga 600. /OVR and /INT2 signals can be found next to each other at the 86-pin expansion connector. /INT2 can also be found at pin 21 of U7 8520 CIA (ODD CIA "A") in the Amiga 500, and /OVR at pin 29 of U5 Gary. /int6 is at pin 21 of the EVEN CIA "B", U8 in A500. /OVR and /INT2 are available on the top side of the 86-position card-edge. Number one is a ground contact, and so is the next one beside it. In older A500 mainboards (rev5) these two positions may form a big unified copper area. When counting the top side positions, /OVR is the 9th, and /INT2 the 10th. In "pin-numbers": /ovr = pin 17, /int2 = pin 19, /int6 = pin 22. Link "Google" for other finds of information.

16 May 2015, 16:39	#4
Yulquen74 Registered User Join Date: May 2013 Location: Kleppe / Norway Posts: 258	Hi, Toni really answered my question. The case is in regard to my FAST-RAM board for A500 which enables the usage of the entire 1,7MB slowfast area in addition to its other memory areas, totaling 12,6MB. My goal was to make it compatible with the IDE68K board (and similar). I have now just made the last 256KB of this area (0xD80000-0xDBFFFF) optional by the means of one of the available switches on the board, so it should now be possible to install in a machine with the IDE68K.

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