Help! an 8-bit CPU for Linux

[eexuke]

I am going to design a high performance 8-bit CPU to run Linux & Staroffice.I am now studying the feasibility of this project.

About the CPU,if I can make it very fast,say,1GHz at 0.13um,maybe it can satisfy my needs.But for the memory and other aspects,totally I have no idea.The bandwidth of an 8-bit CPU is really limited.

Can anybody give me some suggestions?

Thanks & bow !

 

[davorin]

There is no 8-bit linux distro anywhere....and most probably never will (o;

What have you thought about address range?
Why not going with 16-bit and internal 32 bit registers and 32 bit address space? The blackfin DSP is an example 16-bit I know and worked with which has linux support (uClinux).

 

[eexuke]

Thank you for your advice!

Indeed,I am doing the feasibility study since the 8-bit CPU is cheaper and more effective than 16-bit or 32-bit counterpart. I just want to know the difficulties and the bottleneck to implement the linux on a 8-bit machine.

 

[davorin]

Well..maybe you should first start with:

Which CPUs are supported by gcc toolchain...otherwise you have to build own gcc/binutils set for it....though there are a few documents how to port to a new architecture it isn´t that easy...especially binutils is more difficult...

 

[jhonny_yang]

Well..maybe you should first start with:

Which CPUs are supported by gcc toolchain...otherwise you have to build own gcc/binutils set for it....though there are a few documents how to port to a new architecture it isn´t that easy...especially binutils is more difficult...

I don't think so Linux support for 8-Bit CPU but maybe possible for 16 bit CPU.
Operating system only use for complex system.

 

[davorin]

I don't think so Linux support for 8-Bit CPU but maybe possible for 16 bit CPU.
Operating system only use for complex system.

This is exatcl what I alread said in my first post...So please don't just repeat...and..there IS a 16-bit CP running uClinux..it's the Blackfin DSP from ADI...as also mentioned above!!!

 

[eexuke]

Thank you for your kind suggestions.
I know there's no 8-bit CPU that can support Linux now.The bandwidth of 8-bit is really limited for complex OS.But,is ther a way to compensate for it? For example, if the 8-bit CPU and its system bus is fast enough,for example,800MHz max frequency and 200MHz front-side bus,can I run linux on such kind of system?
So I am eager to know the hardware consumption during linux running in order to know whether it is possible to be supported by a fast 8-bit CPU.

 

[davorin]

It isn´t about the MHz (o;

There are many 68k clocked at 16MHz running uClinux (o;

It´s more about internal representation...if you do it like a 68008 with external 8-bit bus only then I see no problems...

For me a 8-bit CPU is like the Z80 with limited address range...and therefore will never run Linux...since it requires 32-bit address space...

 

[eltonjohn]

Hi ... I got interested at this project ...
Let me give you some reflections of my own ..If your real project is to design a CPU and the have it doing some nice .. it makes sense ..
Otherwise .. is just a matter of CPU flavor ... what can be acomplished with a heavy load system running on a light CPU??

In both cases the only CPU that makes SENSE is the AVR !!!!!!!!!!!!!
There is a GNU dev chain ...so you could try to compile Clinux .and
probably those chips are powerful enough to do something useful!
take a look first to see if it hasn't been done yet!..
Now if your main interest is to design a CPU .. well THE AVR INSTRUCTION SET also MAKES SENSE ..
There are some AVR open cores .. at www.opencore.org
at least you won't start from scratch ..and later and you coud try to design a primitive MMU like the one avlaible in the triscend E5 (8051 core
it does some paging by mapping banks .).
So you could start right away with the port of Clinux to the AVR an see what you neet to implement in hardware !
the gnu chain is there ! so are the avr eval boards !

good luck ..!

 

[Ozonehole2k]

The penalty seems to be massive when trying to run 32bit OS with 8bit micro.... The need for extra memory space is the exact reason to go for more complex microprocessor in the first place. Exceptional claim needs exceptional proof to back that up.... It is fine for a hobby project. But, for other work/research oriented projects, you may probably want to think twice.

I agree with eltonjohn that avr is a good starting point. you don't need to invest a lot of time time to upfront to test the idea. It will be slow when compare with your target system. But, the evaluation of overhead is the same... BTW, if you target uclinux rather than linux at start, you don't need a mmu....