6o6 v1.1: Faster 6502-on-6502 virtualization for a C64/Apple II Apple-1 emulator

I'm doing periodic updates on some of my long-term projects, one of them being 6o6, a fully virtualized NMOS 6502 CPU core that runs on a 6502 written in 6502 assembly language. 6o6 implements a completely abstracted memory model and a fully controlled execution environment, but by using the host's ALU and providing a primitive means of instruction fusion it can be faster than a naïve interpreter. This library was something I wrote over two decades earlier for my KIM-1 emulator project for the Commodore 64, and relatively recently I open-sourced and discussed it in detail. It runs on just about any 6502-based system with sufficient memory.

For this update I made some efficiency improvements to addressing modes, trimmed an instruction out of the hot path, provided an option for even more control of the 6502 interrupt flag and implemented a faster lane for direct stores to 6502 zero page (as well as the usual custodial and documentation updates). And, of course, any complex library needs a suite of examples, and of course, any update to a complex library demands new examples to play with too.

So, given that this year is Apple's 50th anniversary (and, as it happens, my own 50th year of existence personally), what better way to show off a 6502-on-6502 virtualization library than with an Apple-1 emulator ... that runs on the Commodore 64 or Apple II? Now yea, verily, this is hardly the first such example and several others have done something of the sort, but I submit that 6o6 makes our take on it here unique, and as a bit of fun we'll discuss the Apple-1's hardware and look at all that prior 8-bit emulator art for comparison (for the C64 and Apple II and even more exotic systems like the SAM Coupé).

The better way to get VICE on Ethernet with SELinux

Although I was a registered hardcore user of Power64 when my daily driver was still a Power Mac, now that I'm a daily Linux user on this Raptor Talos II the best Commodore 64 emulator is clearly VICE, the Versatile Commodore Emulator. It not only has highly accurate emulation, but can talk to real disk drives over OpenCBM (I use it with a ZoomFloppy xum1541) and even emulates a whole mess of peripherals, including Ethernet cartridges like the RRNet and clones (on my real Commodore 128, I use a 64NIC+).

However, I'm a Fedora user and SELinux is on by default. SELinux will really ruin your day here because it (quite reasonably) sees a random user application trying to tunnel out a network connection through libpcap/libnet as a security risk and disables it by policy. You find this out the hard way by trying to enable the Ethernet cartridge from the VICE preferences interface and getting a message you need to run it as root. I don't run things like Commodore emulators as root, spank you very much.

Fortunately, there's an easy, (probably) one time workaround; with libpcap and libnet installed (using tun/tap isn't supported yet), you will have to be root just once to fix the problem. Assuming x64sc (or whichever VICE component you're using) is in /usr/bin, you can give it raw network access with setcap cap_net_raw,cap_net_admin=eip /usr/bin/x64sc. Now you should be able to run it without root privileges and be able to access the raw interface. Here's a little test in Kipper BASIC:

Makes cross-development a lot easier!