Hi Dave,
?
I know SDCC is PC based but it inherent PCisms are notable.
?
Its compiler does not produce great code.? It works and runs
but you would think on a current generation PC there would
be better optimization.? Even for Z80 it does a lot of redundant
stack work and under utilizes the register set.? Actually most
do not as the assumptions of stacks and issues with addressing
modes are a handicap.
?
Code for 6502 is not terrible.? The compiler writer has to get
out of the hardware stack mentality.? ?The 6502 has a limited
hardware stack ( best used for subroutines only) but decent
selection of memory addressing modes.
?
The granddaddy of them all is PDP-11, as that was where C
as we know it originated and many of the nominal K&R pointers,
datatypes and the like are native addressing modes on that
machine. It also had a powerful MMU.? I have several PDP-11
systems.
?
Owing to the period of generation (very late 70s and early 80s)?
one has to expect K&R C is the standard.? Later C# and C++ are?
nearly a decade later.
?
As to IDEs Turbo Pascal and C were later and very good. they
migrated to DOS on PCs.? At that time a step up for PCs
and DOS languages.
?
Bank switching is easy, there is no standard mechanism
and CP/M does not support it (or prohibit it).? ?CP/M
applications?don't know to use it. So...
?
As to MMU and larger than 16 bit addresses, that were Z80
(and friends) were at a impasse.? ?The Z180 has it built in but
it adds little.? The two predominant schemes were whole
Bank switch (whole 64K pages) usually with a small common?
non-banked ram or paged with scatter gather using a
1/4/8/16/32k kb page size.? ?I have such a paged system
(1k page).? ?The real issue is CP/M based system? are flat
64K and programs do not look further.? The most common
use was to put an extended bios and maybe resident system
extensions outside normal workspace the TPA or the Transient
Program Area (from 100h to below the BIOS) and that could
be up to 63K though systems with 56K were considered large.
The other was to use the extended ram as fast disk.
?
Also tried?straight 64K ram system (about 1980) with fast
(ram disk) storage to do virtual paging.? ? Nothing to take
advantage of it and swaping overhead was high.? Worthwhile
but only got used for foreground/background operations
like printer spooling.
?
I also do hybrid...? Myz80 a full z80 system emulation in software
on the PC under linux/dosemu for when? a PC is handy but a
real system is not.? It has all the same tools as my real
hardware and can even transfer files PC space (either way).?
Turns out the PC editors are no better than VEDIT on CP/M.
?
If you want a Unix like system then Usi unix and kin are to
be looked at.? ITs big so banked memory is desirable.
?
That's 50 years of been there did a lot of that.
?
?
Allison
