Reply 20 of 59, by r00tb33r
Why would I need another A500? I've already got two. […]wrote:
I am a bit confused here. Why not just buy an Amiga500++ board. One of them reproduction ones. All you need is the custom chips them self. As they are not produced anymore. That way you can solder and build a brand spanking new a500 Plus machine.
Why would I need another A500? I've already got two.
The point of the project is to re-create Amiga architecture in a homebrew fashion using CPLDs, MCUs, etc, and using none of the original custom chips. I also don't aim for 100% software compatibility. Because I want to run my bus faster than 7MHz (hoping to reach 18MHz) I will also have to forego EPROM and Flash equivalents and replace it with SRAM and a loader MCU that will hold RESET and initialize it at boot time. It will be M68000 based, as I want to maintain the 16-bit bus for design elegance and simplicity. I do anticipate including an IDE controller. The video circuit will be natively VGA-like in terms of signal timings, with modes with and without scandoubling. It will be Franken-ECS, not AGA, but also having more features than plain ECS. Those are just some of the features of the design.
Anyway, you don't to "get" it. I just like working with PLDs. 😎
That will be hard. I mean really hard. And why not have a third Amiga? I have 4 of them already, and I am planning to get at least two more. I have enough PC's and C64's as it is right now (one Breadbin, one Model-C, one 286, four 486's, one Pentium1 and one Pentium3)
Well, I have Computer Engineering education, so I like picking apart old architectures (because they're simpler). Amiga is really cool, it had a lot of things going for it, be it unified memory architecture, the fancy but practical video circuit, the fancy operating system (intentionally vague on it's features), respectable sound, etc. But everywhere where the cheap A500 excelled, it also fell short as a workstation architecture. Around 1990 it no longer made sense to use television-based video modes in a computer, yet Amiga's architecture was designed around TV signal timings. No higher (practical) resolutions, no non-interlaced modes. High density floppies never became common on Amiga, and the ones that were available are a bit of an abomination (dual rotational speeds, WTF?). No chunky pixel video modes. No sound sampling rates that are CD-like (44.1KHz or multiples of it). Sure, you can install cards that remedy some of those points, but at what point do you replace most of the hardware architecture that makes Amiga the Amiga? It just becomes a generic M68K computer, which were actually very common back in the day.
So rather than wanting another Amiga, I want an Amiga like it should have been, or could have been. In my project I will be able to make it a little bit more relevant. For example as I mentioned earlier, I intend to dump TV-based video signal in favor of VGA-like. Sometimes using built-in scandoubling (the address generator will make the Denise equivalent read the same scanline data twice), sometimes with new progressive video modes. I will probably include an interrupt generator that will produce interrupts that will make CD-quality audio more practical to implement, and might extend the DAC to more bits if I feel the need to. I also intend to implement an Ethernet controller based on ENC28J60, because I feel floppies and CDs aren't relevant anymore, though a hard drive is still desirable. Implemeting a minimalistic IP stack will be a major undertaking on it's own. I am planning on a 2MB all Chip RAM configuration, since I consider the unified memory architecture one of the strengths of the simpler Amiga models.
So vanilla Amiga I like studying, but I don't really like using it all that much. Re-imagining it is more fun for me.
By the way, I do like your Amiga project(s). I'll do my best to follow your blog.
PS Sorry about the callous attidude toward your problem, I also have Asperger's and actually do have trouble with daily funtioning. I can barely get myself to work and back, and I live alone, and I do a pretty poor job of keeping my household straight. And I'm in that dreaded hole where I am no longer able to enjoy the things I once enjoyed doing. So I haven't actually done anything related to my hobby for about a year. Nowadays I don't feel like doing anything when I get home after work. My engineering job mostly deals with custom software for broadcast industry. If I had more energy perhaps I would have gotten something better for myself. Call it defiance, but I do not consider myself depressed, or rather I refuse to recognize it as being a thing.