Project Kiwi - an 68k Homebrew Computer

[matthey]

I like the idea of a simple Coldfire system.
Using a PCI video card like a Voodoo3 the system could be powerful enough for an AROS port.
In fact, much of the work done on the 68K version should be easy to re-write.

I have two 200MHz Coldfire CPUs that support PCI. They only cost about $20.
233MHz versions run about $25.

The ColdFire is nice because of the SoC capabilities which are old but fine for a hobby project. The Fido is actually more interesting to me as a CPU and I'm surprised no hobbyists have tried to do anything with it. My main Amiga is a 68060@75MHz with Mediator+Voodoo 4. Despite the slow PCI gfx bus (~8 MB/s), I can load Quake in about 30 seconds and get about 25 fps in 640x480x16 full screen with QuakeGL. I think 30fps would be possible with more optimized code. That's not bad for 90s era hardware .

[haywirepc]

"68000 would be nice.

Personally I'd be interested in a similar machine based around an Hitachi 6309."

You could just buy a tandy color computer III and the 6309 is pin to pin compatible with the 6809 and twice as fast. Many people have done this. I believe someone also interfaced sid chips to the coco... I have a 6309 coco.

[nicholas]

I Will!  Just as soon as I get it published in "Cantankerous Gits Monthly" along with a paper I have in mind about low slung jeans and that crappy Hippity Hop music.  Git Offah Mah Lawn!

Here I am responding to Nicholas' link to the Ubuntu Phone Edition link:



Kids these days - BAH!

:lol:

Not been referred to as a kid for many a decade, I'll be happy all day now.

[nicholas]

"68000 would be nice.

Personally I'd be interested in a similar machine based around an Hitachi 6309."

You could just buy a tandy color computer III and the 6309 is pin to pin compatible with the 6809 and twice as fast. Many people have done this. I believe someone also interfaced sid chips to the coco... I have a 6309 coco.

I've always found the Coco an interesting machine, it's quite exotic here in Blighty. The Dragon series was our nearest equivalent I think.

[nicholas]

That would interest me too.
I have three 63C09s sitting in my spare parts bin (and another installed in an Atari 130XE).
I looked at the predecessor of that Yamaha VDP years ago.
They have overlay and sprite support.

How about multiple 63C09Es running at 3.56 MHz with interleaved memory access? After all, really fast memory is available, and with individual caches the processors could all share the same memory.

SIDs tied to a multitasking system with decent graphics?
Sounds neat.
And I can handle 6809/6309 assembly code.

If only I had the skills to build such a beast!

[bloodline]

I'm not sure. For most instructions the 68000 only accesses the bus every two cycles, where it fetches 2 bytes. I am too lazy to check, but it would not surprise me if the 68008 accesses the bus on every cycle. So it might not make much difference.

That would be reasonable, but I always thought the 68008 was just an ordinary 68000 with only 8data lines exposed, thus is would also suffer the every other cycle memory access penalty.

-Edit- But actually thinking about it, that would make almost all the addressing modes pointless...

[Linde]

I'd love to try that Hitachi CPU!

[persia]

Is it named Kiwi in honour of Trevor?

[psxphill]

That would be reasonable, but I always thought the 68008 was just an ordinary 68000 with only 8data lines exposed, thus is would also suffer the every other cycle memory access penalty.

It's not just a 68000 with 8 data lines, it has a0 as well.
 
My point about the speed was that on the 68000 it would read a word at cycle 0, cycle 2, cycle 4 etc. While the 68008 may read a byte on cycle 0, cycle 1, cycle 2, cycle 3 etc. So as long as you don't require access to the bus then it's the same.
 
If you did need to dma from memory as well as fetching then you could use 16 bit ram and buffer words and allow the second byte to be read from the buffer. However you're getting into being easier to just use a 68000. These days you could probably just use vram or double speed ram as well.
 
A 68SEC000 is probably the best bet & it can be clocked really fast, but the bus can also be configured as 8 bit or 16 bit. MOVE SR is privileged though, which makes it more like a 68010.

[A6000]

Motorolla claimed the 68008 was 30% slower than the 68000 at the same clock speed, which seems an acceptable price to pay for the simpler and cheaper 8 bit computer design it made possible.