(updated on November 5, 2023)
Enhancing the HiTech C compiler for 128KB RAM / 512KB RAM hardware configurations
The HiTech C Compiler v3.09 is one of the best available C compilers that can be used on 8-bit CP/M 2.2 systems.
However, the high quality of this toolset is critically affected by the available RAM memory constraints. It is very frequent that the compiler reports “out-of-memory” error messages for C source files enough small (some hundreds code lines…).
In the same time, currently there are available a lot of Z80 based hardware configurations provided with 128 KB RAM or 512KB RAM banked memory; of course, Z80 may use only a 64KB address space, but in these hardware configurations, the available extra RAM banks can be selected using I/O ports.
This opens the possibility to “enhance” the capabilities of the C compiler, by allowing him to allocate memory in the extra RAM banks.
For the 2 x 64KB RAM systems, this is possible only by keeping a small piece of code ( the “shadow” code) at the same address in both of the 64KB RAM banks, usually on the highest available address space; this code will be responsible with moving bytes from/to the two available 64KB RAM banks.
This way, it is possible to “allocate” memory on the “upper” 64 KB RAM bank, in order to store there data for the C compiler.
For the 512KB RAM systems, a "buddy-system" memory allocator can allocate memory in this 512KB RAM space.
Of course, this means that the C compiler code must be modified, in order to handle these “special” malloc calls.
Obviously, this means some extra code is executed, compared to the "original" HiTech tools, resulting in a longer execution time.
However, this loss of speed ( 10 to 15% ) is largely compensated by the big advantage obtained: to be able to compile larger C source files.
Benefiting from the high quality work of Andrey Nikitin and Mark Ogden, who published the decompiled C sources of HiTech C compiler's toolset on GitHub, I modified these source files to implement this concept of a enhanced C compiler.
The following components were modified:
- CPP.COM
- P1.COM
- CGEN.COM
- OPTIM.COM
- ZAS.COM (replaced with Z80AS, made starting from the Hector Peraza’s ZSM4 published on GitHub)
The included files are built to be used on Z80 sytems provided with 128KB RAM or 512KB RAM modules hardware configuration.
The resulting C toolset can be used on any available 128KB RAM / 512KB RAM Z80 hardware system configuration:
- RC2014 provided with SC108, SC114, SC118, SC150, SC152 or the Phillip Stevens memory module, or the 512KB RAM + 512KB ROM module, or
- RCBUS-based systems provided with SC707, SC714, or
- Z80ALL (which has 4 x 32KB RAM) or
- Simple80 (2 x 64KB RAM)
For RC2014 or RCBUS 128KB RAM systems, the CP/M must be setup using one of the files from the folder PutSys. This is necessary because of the "shadow code", that must be stored to high RAM address space.
The results are spectacular.
Large C source files can now be compiled, without any problem (see the TESTS folder for some examples).
The C compiler's modified source files are included.
See "How to install.txt" for the enhanced HiTech C detailed installation procedure