Project Kiwi - an 68k Homebrew Computer

[Steady]

@nicholas

Really nice looking project. I wish I had your skills.

Just one question. You use a 68008 and say you have 4MB RAM. Since the 68008 only has 20 address bits, are you using bank switching for this?

[ferrellsl]

This project sounds like a somewhat crippled remake of the Sharp X68000.  

http://en.wikipedia.org/wiki/Sharp_X68000

[psxphill]

Just one question. You use a 68008 and say you have 4MB RAM. Since the 68008 only has 20 address bits, are you using bank switching for this?

The 68008 is available in 48 pin & 52 pin versions. The later has 22 address lines.
 
There is also the 68hc001, which is the replacement for the 68008 and can run in either 8 or 16 bit mode & has 24 address lines.

[TheBilgeRat]

After checking the cool youtube vids out, it looks like it was just a one-off by a very talented guy just for fun.  The telnet client vid was neat - especially the refresh rate for top

[Linde]

So...an MC68008 is actually an even crappier version of the 68000.  Sign me up :rolleyes:

Yes, why didn't he put an Intel Core i7 on it? I mean, most things are crappier. :rolleyes:

[Linde]

If speed was really such a concern to any of us, why would we be using Amigas at all?

[Hattig]

It's a nice project, ramming together all the 80s machines.

68008 from the Sinclair QL.
V9990 is an enhanced version of the MSX2+ graphics chip (the chip was produced in the early 90s though).
SIDs from the C64.

I'd say the next step would be to use a full 68000, that 8-bit data bus is going to be holding the CPU back.

[bloodline]

If speed was really such a concern to any of us, why would we be using Amigas at all?

I don't think people are concerned the device will be slow, that's a given. The problem is that the 8bit bus will artificially limit the CPU for no really good reason.

[Linde]

I don't think people are concerned the device will be slow, that's a given. The problem is that the 8bit bus will artificially limit the CPU for no really good reason.

How is that an artificial limitation? The bus is a very tangible and real limitation for any CPU, boo-hoo.

Tell me, if they used a 68000, what would suffice as a "good reason" for that choice?

[NorthWay]

How is that an artificial limitation? The bus is a very tangible and real limitation for any CPU, boo-hoo.

There are no 68000 instructions that are only one byte long. They are all a multiple of 2 bytes.
So a byte wide bus means you need to use at least 2 extra cycles per instruction on a 68008 compared to a 68000. If it makes your machine easier to construct then by all means go for it, but it is like tieing one hand on your back.

[Linde]

There are no 68000 instructions that are only one byte long. They are all a multiple of 2 bytes.
So a byte wide bus means you need to use at least 2 extra cycles per instruction on a 68008 compared to a 68000. If it makes your machine easier to construct then by all means go for it, but it is like tieing one hand on your back.

I know that, but it still doesn't answer my question.

[nicholas]

@nicholas

Really nice looking project. I wish I had your skills.

Just one question. You use a 68008 and say you have 4MB RAM. Since the 68008 only has 20 address bits, are you using bank switching for this?

Oh, it's not my creation, I wish I had the skills!

I just posted it here as I thought people might find it interesting.

[bloodline]

How is that an artificial limitation? The bus is a very tangible and real limitation for any CPU, boo-hoo.

Tell me, if they used a 68000, what would suffice as a "good reason" for that choice?

I said "artificial limit" because the 68000 works best with a 16bit bus.

[Linde]

I said "artificial limit" because the 68000 works best with a 16bit bus.

What does that have to do with the 68008? The 68008 works best with an 8-bit bus. There is no artificial limit imposed.

Seriously, the thing runs a line number BASIC editor, has a VDP from the early 90s, and a couple of buggy sound chips from the 80s, and the first thing you can think of as "artificially limited" is the CPU? It's a dated and inefficient design, but that's obviously the whole point of the project. If he wanted to build a computer without "crippling performance issues" he wouldn't have used any CPU from the 68k series.

So I think you should all stop whining about a few extra cycles spent on memory reads and realize that in terms of performance, the 68000 and the 68008 are two drops in the bathtub you get when if buy a decent cell phone. Whatever argument you are making, it could as well escalate into "why not a 68020", "why not a Coldfire", "why not an ARM" or "why not Intel". But it doesn't, because you have no sense of scale.

[AmigaClassicRule]

What does that have to do with the 68008? The 68008 works best with an 8-bit bus. There is no artificial limit imposed.

Seriously, the thing runs a line number BASIC editor, has a VDP from the early 90s, and a couple of buggy sound chips from the 80s, and the first thing you can think of as "artificially limited" is the CPU? It's a dated and inefficient design, but that's obviously the whole point of the project. If he wanted to build a computer without "crippling performance issues" he wouldn't have used any CPU from the 68k series.

So I think you should all stop whining about a few extra cycles spent on memory reads and realize that in terms of performance, the 68000 and the 68008 are two drops in the bathtub you get when if buy a decent cell phone. Whatever argument you are making, it could as well escalate into "why not a 68020", "why not a Coldfire", "why not an ARM" or "why not Intel". But it doesn't, because you have no sense of scale.

WOW! Now that people is what we call a sass! Though, I have to admit you are right 100%.

The guy just made a toy...it is a toy..really. It may be a Commodore 65 duplicate without us knowing. Personally I will buy it instead of gp2x or Nintendo DSi, or PSP. I consider it an entertainment system, a console and so forth so I will buy it for the games it will be developed for it. The graphics are great it have potential of having awesome sweet (good quality graphics) games like SNES, Genesis etc....so why not? I will buy it.

[TheBilgeRat]

So I think you should all stop whining about a few extra cycles spent on memory reads and realize that in terms of performance, the 68000 and the 68008 are two drops in the bathtub you get whenif buy a decent cell phone.

I know it may make you feel very clever to compare one-off hobby projects or any non-cellphone platform that contains an ARM chip to a cell phone, but it just comes across as ignorant.  A smartphone is not a general purpose computer, even if its quad core and running at 1.6Ghz+.

When I read the OP, it made it seem as if this guy was going to do a production run of underpowered 8bit-ish "hobby" computers.  I suppose if assembling one for the express purpose of saying you did is your thing, then all the power to you.  What I find hilarious is that a one-off 8 bit hobby computer is able to have even basic network connectivity, where here in amigaland is only possible in an easy sense if you have an amiga with PCMCIA.  While some may find projects like this inspiring, I just find them sad that we have no hardware guys able to shoehorn some easily available componentry into our miggys for a reasonable price (besides Jens, and I don't really consider his prices all that reasonable, even if his hardware is nice).

More and more it seems Amiga, if compared to comic books, is not the series you enjoy to read and dog ear your favorite pages, but more the series you buy off the shelf, stick in an acid free sleeve and bring out to sell later on when you need a new bathroom.