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Re: Possibility of open-sourcing GS/OS
Michael Black wrote:
The Wizard of Oz (wizard@emeraldcity.gov) writes:
The original UNIX (without GUI) was apparently four Meg.
I'd say that's a high figure. UNIX dates from the early seventies, and
four megs would be a lot at that time for a minicomputer. There
were microcomputer based systems for UNIX twenty years ago, and they
were more like 512K of RAM. Unfortunately, I don't know where I put
the system adminstrator's handbook from circa 1985 that talked in
terms of large systems that are miniscule compared to the home computers
of today (minus the number of serial ports and users).
Right. The only way to get to 4MB for the early versions would be
to add in all the commands, which never co-reside in memory.
The kernel was quite small as OS's went in its day.
While there seems little point in trying to create something better
at this point, one thing a few big 6809 systems did in the late seventies
was to add processors to handle serial and parallel ports. Shifting some
of the demand off the 65816 likely would help to improve operation, not
just in terms of space considerations but in keep the load on the processor
down. Given that small amounts of ram rely on swapping to disk, having
something to swap to is vital. But a hardware ramdrive might help
in that arena, adding memory not to the address space but in a separate
area connected by the parallel bus.
Since it is relatively easy to equip a IIgs with 4MB (or more) of
directly addressable memory, I don't think that much swapping would
be needed. (Nor would it be very fast, at a peak transfer rate of
1MB/second.)
And the data transfer rates of serial and parallel ports are so
low that a little interrupt service time need not have much
performance impact, unless it is done poorly.
The real performance problems of small OSs come from poor structure,
slow algorithms, overly generalized interfaces, and too-fine-grained
modularity. If those pitfalls are avoided, a very fast kernel can be
written.
-michael
Music synthesis for 8-bit Apple II's!
Home page: http://members.aol.com/MJMahon/
"The wastebasket is our most important design
tool--and it is seriously underused."