[TUHS] V7/8086 I'm a bit behind the times here, but...
peter.jeremy at alcatel.com.au
Wed Jul 2 08:19:34 AEST 2003
On 2003-Jul-01 18:16:27 -0400, Steve Nickolas <usagi.tsukino at pinku.zzn.com> wrote:
>I already had some ideas, and when I saw something called "v7upgrade", a weird thought came to my head...
>I'm wondering if any gurus out there would be able to point me in the
>general direction, as far as getting V7 stuff running on an 8086,
>perhaps a full V7 system. Something like v7upgrade but including a
>kernel and bootloader. I don't know. Just musing...
I've also been considering this in the background ever since "ancient"
Unix became available. At least one other person has posted that they
did actually do a suitable port.
- 8086 has no hardware protection. You'd need to go to the 80286 to
get any inter-process protection.
- 80x86 16-bit memory management is far more primitive than the PDP-11.
Given the requirement for data and stack addresses to be in the same
address space (assumed by virtually all C programs), the total data+
heap+stack space required for a process must be pre-allocated and
there is no protection between heap and stack.
The main reason I've never proceeded is the lack of a suitable C
compiler: 16-bit 80x86, open source, able to run in 64K I+D mode, and
generating half-way decent code. (Without the last requirement, the
kernel and some of the larger userland utilities will probably be too
Supporting overlays would add the requirement to handle mixed-mode
code, support segment overrides and 'far' objects.
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