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[LoadWB]

I decided to start out with an "easy" project. I thought it would be really neat to have a card containing ChipRAM and a 2.5" hard drive which slides into the A500 trap door.

The idea was to have a hard drive interface for the 500 which would not require raising the 68000 any higher out of its socket, and without a side car. Ultimately, my thought was to have a completely self-enclosed A500 with no externally visible signs of upgrades, but hiding a lot of functionality under the hood. Doing this, one could build a system holding a 50MHz Derringer, an ICD FFV, a hard drive, and extra ChipRAM, all while looking completely stock.

Upon perusal of the A500 schematics, I find that the trap door slot does not hold any of the signals I need for an IDE interface. So, that shuts out the plug-and-go idea for the project, but it doesn't leave me out completely.

Rather than raising up the 68000 higher in already cramped quarters, I thought about a logic board a la BaseBoard, which put 4MB of FastRAM in the trap door via a logic board which sat in the Gary socket.

I was hoping to fish for some comments on the idea presented here. I think that 500 is largely ignored in our current affairs, and probably rightly so considering the viable alternatives available. I'm not planning to make a zillion dollars and introduce anything ground-breaking here, I just want a project to start me hacking on the Amiga hardware.

[Jeff]

I always kind of wanted to do the same thing with one of my 1000's.

[whiteb]

Are you sure there are enough of the correct signals for the 500's trapdoor ?

I do not know what signals there are there. And is there enough clearance from the RF Shield/Keyboard ?

[LoadWB]

whiteb wrote:
Are you sure there are enough of the correct signals for the 500's trapdoor ?

I do not know what signals there are there. And is there enough clearance from the RF Shield/Keyboard ?

I mentioned in my OP that the signals I need are NOT there, which is why I would need to logic board in the Gary socket. My BaseBoard did fit, albeit snugly, under the RF shield and keyboard. I've already played enough to find that a 9mm or 12mm 2.5" hard drive set far enough to the back of the trap door slot easily fits under the keyboard.

I have also entertained the idea that I could probably just fore go the hard drive and use a CF card instead.

But most people tinkering with the guts of the 500 have thrown that out a long time ago ;-) [EDIT] The RF shield, I mean.

[whiteb]

Ah, so thats why my Axram (4x1MB Simm Trapdoor) has a Gary adapter.

[Zac67]

As long as you run all the required signals to it, you can put your IDE controller where you want.

Since Gary lacks registers you won't find any data bus and low address bits there. The easiest way to get them is actually the CPU socket or the expansion slot.

[alexh]

Why not create a sidecar addon? All the signals are there, it doesnt have to be physically very big if you use a CF card rather than an IDE disk.

Personally I think doing any A500 hardware right now would be mad. MiniMig is the place to put your efforts right now.

[LoadWB]

alexh wrote:
Why not create a sidecar addon? All the signals are there, it doesnt have to be physically very big if you use a CF card rather than an IDE disk.

Personally I think doing any A500 hardware right now would be mad. MiniMig is the place to put your efforts right now.

Thanks, but I already covered all of your comments.

Aside from that, I personally don't think the MiniMig needs my amateur assistance or mucking about. And I don't have one.

[LoadWB]

Zac67 wrote:

Since Gary lacks registers you won't find any data bus and low address bits there. The easiest way to get them is actually the CPU socket or the expansion slot.

Good points. I'm trying to stay away from the CPU and expansion slots for this project, so Gary seemed a most likely spot.

I can pull A2-A5 from CNX, and A17-A23 from Gary. Missing A16, I can't set a base address of $DA0000, I'd have to use $D40000 instead (or any combination in the peripheral range that A17-A23 will allow.) And I only need A2-A4 for the IDE drive.

But then I'm missing the raw data buss lines in both places. Makes me wonder how the BaseBoard worked... maybe it used the arbitrated data buss (DRD15:0). It looks like it could have manipulated the Gary signals to connect DRD15:0 and D15:0 using the tri-state latches.

Now I'm not so sure that this will all work the way I want: I have to look up possible conflicts at $D40000 and if using the DRD buss will work for my needs, maybe with some more logic. A challenge :-)

[LoadWB]

DOH! I need A12 and A13 also, which I can get from neither Gary nor CNX (the trap door expansion.) Looks like all this is moot. It seemed like a cool idea, though :-)

[alexh]

Why do you think it is a bad idea to raise the 68000 chip?

Surely it's just as bad as raising the Gary chip?

I conceed that the Gary is smaller and the socket cheaper, but if the 68000 has all you need... why not?

Is it because you already have an accelerator fitted?

[LoadWB]

Seriously, not trying to be a dick or anything, but I answered that in my original post, also.

[alexh]

It wasnt clear in your original post what you meant.

[Argus]

I for one would like to see any new hardware for the original Amigas. The A500 is quite expandable, you can even add clockports to it now thanks to Jens, which opens up fast serial, soundcards, and USB (if you have a 68020+). The problem with 68000 socket add-ons, however, remains the height concerns the invariable piggy-backing causes.

One idea to get the signals is to run some wire wrap from the 86-pin side connector to somewhere else inside the case. There is just enough room to keep the sidedoor on the case if you construct a thin enough edge connector. Then you'll have every signal imaginable right inside the case. There may be a limit on the cable length, however, and there may be conflicts with a particular accelerator in the 68000 socket.

Good luck with the project.

[Tron2k2]

A company called ICD made an IDE interface expansion for the 500, called the AD-IDE or ADspeed with IDE, it had a double speed 68000, 16k of static RAM as a cache, and an IDE interface for a 2.5" drive. You see them on eBay from time to time. Maybe you could base your project on that or something similar?

Hey, if you make a few of them I'll buy one! I'd love to rock a hard drive in my A500 :-)