The A 1200 Trapdoor interface...

[McTrinsic]

Hi all,

I just was browsing the web when I found an interesting bit of info. Only to lose the link, though...

Anyway,  I read that the A1200 trapdoor slot would not be that different to some sort of other interface, i.e. Zorro-Slot or maybe CPU-Slot of the A4000/A3000 ?

Anyone able to say something about it? On the page I read about that, it seemd to actually make sense, since why would Commodore develop two (or more) totally different interfaces when modifying an existing one would work as well...

Or is it maybe more like the A500-trapdoor-slot? A500 with PPC!

Just wondering,
McTrinsic

[odin]

The A1200 trapdoor slot is only found on the A1200 :-).  A4k/A3k FastSlot is different. As are Zorro(I/II/III) and the A500 and A600 trapdoor slot (maybe those too are the same though?).

[Argo]

I don't think he means "physically similar".

[bloodline]

odin wrote:
The A1200 trapdoor slot is only found on the A1200 :-).  A4k/A3k FastSlot is different. As are Zorro(I/II/III) and the A500 and A600 trapdoor slot (maybe those too are the same though?).

The A500 and A600 trapdoor slots are nothing more than Memory interfaces. Nothing else can go in there.

The A1200's Trapdoor is a CPU/ZorroII type slot, it has all the signals requiered to implement those slots anyway.

[odin]

Argo wrote:
I don't think he means "physically similar".

As did I :-).

The A1,2k trapdoor slot doesn't require glue logic for an A3k/A4k CPU card then? (Ignoring the physical fact).

[SamuraiCrow]

@bloodline

There was a PC-emulator called AT-Once that plugged into the trapdoor slot on A500.  Since the enhanced chipset maps the trapdoor slot memory in as CHIP memory trapdoor slot expansions other than memory weren't popular on A500.

[Kronos]

@SamuraiCrow
The AT-onr that I know of was slapped between CPU and CPU-socket.

I think you had the KCS-Power-board in mind, XT-compatible with
768k of RAM. This one was only seen as "memory" for the A500, and one
could even use it as 512k expansion for the A500.

The only think that I don't know is wether it supported both addresses (for Chip
and "Ranger" mem).

[PaSha]

@Odin:
The only way (AFAIK) to stick an A3/4000 accelerator on an A1200 is via the Micronik Z3i A1200 Zorro3 backplane. And this board most likely has a whole lot of glue logic (and doesn't give you Zorro3 DMA), since the A1200 trapdoor slot only has Zorro2 signals (because of the 68EC020 having a 24bit adress bus) whereas the A3/4000 cpu-slot has Zorro3 signals.

-Paul

[seer]

The only think that I don't know is wether it supported both addresses (for Chip
and "Ranger" mem).

IIRC that depends on the A500 model (A500 it was "slow/Ranger mem, on a A500+ it was chip).. However I recall it was either 512K Mem and 512K ramdisk or 1Mb Chip or something also depending on the model/chipset....

[McTrinsic]

@PaSha

since the A1200 trapdoor slot only has Zorro2 signals

Does that mean that the A1200 trapdoor slot effectively is a Z-II Slot?? Or are there additional signals?

I meant the original posting so that I wondered if the A1200 trapdoor slot was "logically" similar to any other Slot found in Amigas.

I mean, physical adaptors should be possible to make


Have fun,
McTrinsic

[Kronos]

@McTrinsic
Zorro1 (side connector on A1000/A500 and MMU-slot in A2000) is just an unbuffered
68000-bus.

Zorro2 is a buffered 68000-bus.

A1200-trapdoor is an unbuffered 68020-bus.

[bloodline]

Kronos wrote:
@McTrinsic
Zorro1 (side connector on A1000/A500 and MMU-slot in A2000) is just an unbuffered
68000-bus.

Zorro2 is a buffered 68000-bus.

A1200-trapdoor is an unbuffered 68020-bus.

Zorro has some other bits and bobs in there as well :-)

The A1200 trapdoor has other signals as well as what is needed to implement ZII (notable are the audio signals).

[Karlos]

stupid question

Are the audio signals there analogue or digital? I'm guessing analogue.

-edit-

The only thing I ever played with was the /RESET line, which I tapped off to initialise my old (internally fitted to the desktop 1200) DB50XG card.

[bloodline]

Karlos wrote:
stupid question

Are the audio signals there analogue or digital? I'm guessing analogue.

-edit-

The only thing I ever played with was the /RESET line, which I tapped off to initialise my old (internally fitted to the desktop 1200) DB50XG card.

The Audio signals are Analog, they are resistively mixed with the Paula output and piped through the RCA's at the back.

It was for the CD1200 rom drive that would put the AUDIO CD output through them.

[Karlos]

Well that *does* give me an idea.

My CDRom has no output beyond the headphone socket. So it should be possible to tap those lines and connect them to a standard header for a CD audio cable, right?