minimig 4000

[AJCopland]

I don't necessariyl disagree with your ambition but I think that you're going to need to put some effort in yourself if you want to get this started.

Firstly however a couple of things. SDRAM PC100 or PC133 is seemingly much easier to implement and is on my own list of things todo right after "build my first MiniMig v1.1". DDR and DDR2 has been mooted as difficult for hobbyists due to timing constraints. So for now I'd stick with SDRAM, its cheap and plenty fast enough for MiniMig.

Forget sockets and just go straight for an '060 if you're wanting to upgrade the CPU. It makes the design easier as its running at the same 3.3v as the FPGA so theres no level shifting.

CIA's are, as far as I know, replicated within the FPGA using Verilog. No need for anything external.

To support AGA and '060 you're gonna need a 32bit data bus, might as well support a 32bit address bus at the same time. That means quite a few more pins available on the FGPA so you'll be going to BGA based FPGA.

ATA/100/133 IDE is nothing I've heard talked about so I don't know how much harder it'd be than any other IDE mode.

Zorro support. I have not a clue :-D

Basically I think that if you want to see this become a reality then you should break it down into the tasks required for each stage. Once you've done that pick the first one that you feel is crucial and look into the parts and things that you'd need to change to make it happen! You don't need any experience to that bit but it'll mean that when you come back and need experienced help you've done most of the legwork!

Good luck.

Andy

[AJCopland]

A6000 wrote:

downix wrote:
How about we get an A2000 replacement going first, then let's work on the next step?

The responses to this thread have been so negative that nothing will be done.

Actually you're replying to Downix who has started to do something. He's right though that you've got to do these things in little steps because that's how you make sure that they actually get done!

Andy

[AJCopland]

A6000 wrote:

Well I will admit that this task is beyond me, but well within the capabilities of others on this forum. but I would start with the circuit and pcb design of the 4000D and:-
1. replace fast slot with cpu socket, this can accept 040 or 060 since there will be more 040's available than 060's. the programmable clock speed allows any speed version to be used.
2. replace AGA chipset with minimig FPGA.
3. implement memory, SDR is old and expensive, DDR2 may be more economical.
4. implement hard drive interface.

Job done?

P.S The PPC can go on a board plugged into the cpu socket.

Someone else has already stated it but you're talking about something like the Clone-A. Where you start by replacing each of the chips in an A4000D motherboard with fpgas and "just" duplicate the motherboard design.

That won't really work for several reasons. The main one being duplicating the motherboard design as it isn't really easy or possible for hobbyists and it's not economical for a professional company.

Don't let that be the end of the idea though.

What I meant in my reply was to start from the MiniMig v1.1 as your base. Decide what you want and then figure out what you'd need to do to change the v1.1 into the thing which supported that idea. Then you move onto the next part of it and do the same. Repeat until you've got all of your features and voila! You'll have got a MiniMig4000.

Also as someone already said, SD-RAM is still cheap and plentiful due to its use in just about everything from washing machines to set-top-boxes. Also for the speed of the 060 and PPC chips its plenty fast enough. DDR can come later but start off easy!

For the A4000D you'd want what? an '060? Ok figure out how to add that, just with pen and paper compare what the MiniMig has now and what you want it to have. Go and lookup the datasheet on the Freescale website and see if as alexh says it uses 3.3v or 5v for it's IO lines. If it does use 5v then you know that you'll need voltage shifting hardware.

Make all of the things that you discover into a list of things that you _reasonably_ think you'd need to do, but don't know how, to put a 68060 processor onto a MiniMig v1.1 physically. Don't even worry about the code used in the FPGA for now just think about that one small area.

Once you done that, come back and ask again about how to actually do those things or see if someone would be willing to design them for you. Basically get someone to sanity check them.

Andy

[AJCopland]

I think there's more to having AGA support than just changing the Verilog. It'll need the data and probably address buses upgrading to 32bit as well as running at a higher clock speed. Then to actually support software which expects AGA you'll probably need at least an '020 processor.

Basically take the A1200 as a minimum spec' for AGA and upgrade the MiniMig v1.1 to it.

From the way I've just written it that doesn't actually sound like too onerous a task :-D but I bet in practice it won't be so simple!

There seems to be a fairly common theme in peoples postsa bout AGA probably not fitting into the current FGPA which I'm curious about. I seem to remember Dennis stating that he was only using about 60% of the current for OCS. Now the difference between OCS and AGA wasn't that staggering, a faster and wider data bus. Extra registers etc, but it was mostly described as evolutionary rather than revolutionary.

What I'm trying to say is that I've heard no good argument as to why AGA shouldn't fit within the current FPGA. Has anyone got any knowledge about this? It seems to be a bit of an inaccurate science guessing how much space any given implementation might occupy.

Also a CPU fast slot isn't going to make a v1.2 any better at supporting AGA as it'll still be connecting to the same FPGA via the same 16bit wide data path running at half the clock speed of AGA. Since a large part of AGAs benefit was actually the 32bit data bus and the doubled bus clockspeed over the OCS/ECS system you'll lose whatever benefits you hope to gain by having it.

Just my opinion obviously.

Andy

HenryCase wrote:

AeroMan wrote:
I think if AGA compatibility is the target, we should have that in mind when doing any board. The hardware should be capable of supporting it, and we can grow the software slowly from OCS to ECS and then AGA without doing new boards. This keeps costs acceptable for us hobbists.

Aeroman, this is very important, and it's something that hasn't been discussed much. The key to doing this is expandibility, which is the one major weakness with the v1.1 PCB. Let's say an AGA solution was made. It seems very likely that AGA wouldn't fit on the current design, so those people who want it have no choice but to upgrade to a newer PCB revision. If we had something like the CPU Fast Slot then we could design an upgrade board for the existing design, with an FPGA providing the extra processing capacity. People who hadn't bought a Minimig before this time could just buy a newer version of the PCB with the expanded capabilities built in.

I don't know if Minimig v1.1 had enough I/O pins on the FPGA to handle an expansion port, but if TobiFlex does release his code then we'll have plenty more I/O pins to play with. Downix, how many pins does your A500-like expansion port need?

If an expansion port is included in v1.2 a greater number of early adopters have more versatile hardware sooner, which in turn will speed up development. Any thoughts?

[AJCopland]

downix wrote:
92, but I wasn't using "pins" but a card-edge.

If you don't mind me asking what kind of connector are you using? One of the MCA style edge connectors like the ones on the CD32 or one that matches the original A500 more closely?

I was thinking that if you're making a connector design then it's not going to be readily usable by the old A500 expansions due to the 3.3v and 5v issues. So why not make it using a more common and easy to source connector type?

Andy