[Colchester] CP/M

[Chris Pritchard]

YAY ZILOG Z80!
On 5 May 2008, at 12:58, Wayland Sothcott wrote:

> Toby Whaymand wrote:
>> Hi Wayland
>>
>> I don't know if you know this but the guy who sold MS-DOS to  
>> Microsoft
>> ended up in court back in the early 1980's in which he admitted to  
>> "Low
>> level copying" of the CP/M  code which is owned by Digital...
>>
>> In the book Accidental Empires by Robert Craingely that was published
>> back in 1990 he argues that if Digital were not so slack, not so laid
>> back they could of been were Microsoft is today!
>>
>>
>>
>> _______________________________________________
>> Colchester mailing list
>> Colchester at mailman.lug.org.uk
>> https://mailman.lug.org.uk/mailman/listinfo/colchester
>>
>>
> Toby,
>
> I know CP/M and MS DOS were very similar. In fact the Zilog Z80  
> which CP/M ran on was a derivative/copy of the Intel 8080. The Z80  
> chip by comparison was very powerful but Intel then did the 8086  
> with it's segmented addressing allowed you to address 1Meg of ram  
> rather than 64k of the Z80. I think this also played a big part in  
> the success of MS DOS. The Z80 still has the best Interrupt  
> structure, the device places it's number on the data bus when it  
> hits the IRQ line, providing up to 255 Interrupt channels. The 8086  
> only had 8, cascaded into 15, this is still a limitation to this  
> day! Meanwhile Motorola had the 6809 and the 68000 with innovative  
> relative addressing meaning the operating system did not have to  
> relink code depending on the location in memory the program was  
> loaded to. Sinclair, Apple and Comadore were big users of the  
> 68000.  Apple switched to the Power PC but strangely switch to Intel  
> when the X-Box 360 switch to the Power PC. Acorn of BBC Micro fame,  
> developed the Acorn RISC Machine spawning ARM (Advanced Risc  
> Machines), this is the chip found in almost every PDA today. Linux  
> runs on all of these but Windows is stuck on the x86 family with a  
> special version  available for the ARM, but that's really just  
> Windows in name, not the same OS. I like the fact that you can get  
> Debian for the Broadcom RISC (Reduced Instruction Set Cpu) as used  
> in the Cobalt Qube 2 and the Links WRT54G and the Buffalo WHR54GS.  
> It means you can turn virtually anything into a Linux server.
>
> I used to write code in 'C' for the Z80 for embedded systems. With  
> only 56k of ROM the code had to be very efficient. An operating  
> system would have been nice, then I could read and write disks and I  
> would not have had to write my own network stack. However in many  
> ways having an OS is cheating and opens up insecurities. Code burned  
> into a chip that cannot be altered and can only run the one program  
> is far more secure than having an operating system that can be asked  
> to run a different program. Many of the devices with a CPU today run  
> an operating system, Linux or VX Works or other embedded OS, this is  
> a great opportunity to Linux fans to change the way these devices  
> work.
>
> Wayland.
>
>
> Wayland.
>
> _______________________________________________
> Colchester mailing list
> Colchester at mailman.lug.org.uk
> https://mailman.lug.org.uk/mailman/listinfo/colchester