Assembler recommendations for Orton 3C

[James Harland]

Hello everyone,

When I started learning Z80 assembly last year, it was on the ZX Spectrum and ZX Spectrum emulators, following a course which used the sjasmplus assembler, so that's the one I've stuck with for programming the Orton 3C.

I have come across some limitations though - sjasmplus is mainly aimed at ZX Spectrums and Amstrad CPCs, and so for example I cannot create a plain 128K (non-banked) ROM image - I have to create a 64K one, and then pad it out with truncate on the command line.

While this works, it has got me thinking, whether I should find a more generic Z80 assembler, that would allow me to make the Orton3C.rom image without an extra tool.  Any recommendations?

More generally, is there a gold standard for Z80 assemblers in the wider community, one I should consider using for sharing code with the widest reach?

I'm using some variant of Debian GNU/Linux on each of the machines where I would run an assembler.

Thanks,

James

[Ed Silky]

I use the UNIDOT macro assembler and linker (z80asm, ulink) that I started using in the late 70's. I use it for everything except modifications to RomWBW or things I want to actually build on my Z80 CP/M machine. For those, I use TASM, uz80as, and the assembler in the Hi-Tech C package.

-Ed 

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[Alan Cox]

For general stuff I use my own assembler, but it's really oriented around a different workflow, C preprocessor and for the C compiler so it's probably exactly what you don't want.

For CP/M type stuff and when I need to work with "classic" Z80 asm I generally use ZMAC, both the classic zmac on CP/M which outputs files for CP/M in standard link format and on Linux etc which is a rather more sophisticated beast. With a bit of care on macros and not using 0xFF but the classic 0ffh it's possible to keep the same code buildable on either

 48k.ca is the home of zmac and the matching CP/M compatible linker etc and it's still actively maintained.

Alan

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[Jon Jones]

I've flipped between various Z80 assemblers whilst playing with RC2014 kits. My current favourite its Sjasmplus which is still in active development: https://github.com/z00m128/sjasmplus

Jon

[Robert Price]

I just use sjasmplus. It’s a good assembler, and it works well on my Mac. When building ROMs I usually just build the various images and “cat” them together to get a ROM the correct size.

Rob

> On 1 Mar 2026, at 12:14, Jon Jones <gordont...@gmail.com> wrote:
>
> I've flipped between various Z80 assemblers whilst playing with RC2014 kits. My current favourite its Sjasmplus which is still in active development: https://github.com/z00m128/sjasmplus

> To view this discussion, visit https://groups.google.com/d/msgid/rc2014-z80/50288140-C1BB-4C07-A229-20219D7E2F68%40gmail.com.

[Spencer]

Just to add another option to the list, I generally use the online asm80 assembler https://www.asm80.com/#

This produces an Intel Hex file output, then I use hex2bin to get that in to a file ready to burn to ROM.

Spencer

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>

[James Harland]

Hi everyone,

Thanks for your recommendations. I am encouraged to keep going with sjasmplus, but I have also had a look at some of the other options you mentioned. I needed zmac to compile this Pacman game for my RC2014 Classic ][ today, but I had to  use it on Windows, I haven't got it to compile on Linux yet.

Spencer - I did't have much joy with asm80 online in the past, but maybe I should revisit it now I understand a bit more about compilers. In the meantime, I have installed asm80 on Linux and will use it to add my routines to the Orton ROM, to stay compatible with what you have put up so far.

For what it's worth, I also installed zasm on Linux, which creates the Intel hex files which the small computer monitor needs, which I have learned are different from the hex files produced by xxd...

So I guess it's horses for courses, I'll use different compilers for different needs...

And Robert thanks for reminding me about the option to cat files together, I keep forgetting about this little Unix tricks.

Thanks everyone,

James

[Robert Price]

No problem, James.

I got your Kill The Bit game working on my Orton 3C.
https://mastodonapp.uk/@robertprice/116164970981468853

Cheers

Rob

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[James Harland]

Hey Rob, that's really cool to see it out in the wild like that! Though to be fair only four lines of code are "mine" - the rest is the original source. My next technical challenge is to figure out how Mastadon works :-D

I realise that halfway through my previous post I started saynig "compiler" instead of "assembler", probablly as I was thinking about compiling zmac on Linux, which in the end I managed to do btw.

[Jon Jones]

Spasm has *just* gained support for creating Intel Hex files suitable for use with SCM.

J

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