Show HN: Cross-Platform Apple IIe Emulator Written in Go | Hacker News Reader

Show HN: Cross-Platform Apple IIe Emulator Written in Go

octalyzer.com

103 pointsempressplay31 comments

I've been working on and off on a Nintendo DS emulator 100% written in Go. You can have a look here: https://github.com/rasky/ndsemu/

It features both the 2D and the 3D engine (with a full software rasterizer with poly-fillers generated through go generate). It's highly concurrent (each graphic layer is drawn in a different goroutine and then mixed together). The ARM interpreter is also generated via go generate.

I'll add some screenshots at some point.

I think Go has great potential in this area. Some emulators (? PCSX2/Dolphin/...) are famously stuck with very few threads owing to the design of the underlying hardware, so anything that encourages extracting parallelism from within each subsystem could potentially be a major performance win.

Cycle-perfect emulators at least for typical 8- and 16-bit systems need to run each emulator subsystem (CPU, video, audio, ...) in lock-step for each clock cycle. Spreading those emulator systems over multiple threads would mean that the threads need to synchronize with each other after each step (which is just a few host CPU instructions long). It might be easier for more modern hardware where subsystems are much more decoupled from each other (and I guess with Moore's Law dead this is our only hope to emulate more modern hardware in the future).

That's true. In the case of Nintendo DS, I'm aligning doing line-based emulation; so I first serially emulate the two CPUs (I could in theory parallelize then, but I haven't properly design the emulator around this, so all memory-mapped callbacks are not concurrent safe), and then emulate the graphic subsystem for a single line, spreading the different layers across different goroutines.

This means that goroutines synchronize 263*60 times per second, which is something. I measure a high contention, so I'm not even sure it was worth in the end, but I thought it was a good experiment to attempt :)

Another Go-related thing I did was using struct tags to configure memory-mapped registers in a declarative way. See for instance: https://github.com/rasky/ndsemu/blob/master/irq.go#L13

where I configure the memory-mapped registers of the interrupt controller; "wcb" / "rcb" tags stand for write/read callbacks, which means that specific callbacks (with names matching the register names) will be called for each read/write operation; this is all achieved through reflection. The same applies to mapping the whole register bank, which is done here: https://github.com/rasky/ndsemu/blob/master/nds9.go#L69

The memory subsystem handling these and more features is in emu/hwio, and I'm actually pretty proud of it. For the memory mapping itself, a radix tree is built which is quite quick to lookup and doesn't require much barcoding.

In fact, the whole "emu" package is a generic framework for emulators in Go, and I plan to reuse it in the future :)

The Octalyzer has separate threads for cpu, sound, memory, networking, graphics and the main opengl loop. We use vertical blanking and sound timing to keep it all in sync.

nice what do you use for displaying graphics ?

For interfacing with OS (window, sound, input), I use SDL bindings for Go (go-sdl2). Graphics is 100% being made in RAM pixel by pixel, so SDL is blitting the final image (see the emu/hw package).

thanks

Currently the Octalyzer features full-screen Apple IIe emulation with decent compatibility, USB and mouse-controlled joystick support, cloud disk library (when logged-in to Octa-Link), 3D camera support, 3D LOGO, enhanced BASIC interpreters, custom file browser and editor, and remote screen sharing.

Does it have a CRT filter?

A lot of these retro games don't look so authentic on LCD screens because things like blur and shadow masking were actually used by the designers of the original games.

http://filthypants.blogspot.com/2015/04/more-crt-shaders.htm...

Thanks for the link! We don't currently (although there is some rasterisation provided by the OpenGL rendering) but we'll look into some CRT shaders =)

I could care less about games looking like they're "authentic" WRT to curvature or phosphor grid pattern, but things like aspect-ratio correction (non-square pixels), colour switching[0], or cheap transparency tricks through composite[1] are another matter entirely.

[0]: http://www.aaronbell.com/secret-colours-of-the-commodore-64/

[1]: http://nerdlypleasures.blogspot.fr/2015/03/the-case-for-comp...

Reminds me of the AppleII+ simulation from XScreensavers:

https://www.youtube.com/watch?v=p3QZqhp67l8 http://manpages.ubuntu.com/manpages/trusty/man6/apple2.6x.ht...

So cool. I'd love to read the source if it's available?

An emulator has been my "bucket-list" ever since I became a software engineer. I still haven't done it...Do you have any good pointers for someone to get started with making an emulator (particularly for someone who works almost exclusively with with server-ey stuff)?

Definitely look into CHIP-8, it's more of a virtual machine than an emulator, but then what's the difference at the edges!

One of the screen-shots looks like Flappy bird:

http://octalyzer.com/wp-content/uploads/2017/02/oct16.png

It's flapple bird:)

I'm afraid this does not appear to work on my system (Ubuntu 16.04, 64bit). None of the key combos work (Shift-ctrl-` etc.), and dropping an image just crashes it. And I was all geared up for karateka...

We will check it out thanks!

Auto updating? You must be joking.

Also, a single binary file download without even a checksum (let alone the source)??? No thank you.

You don't have an application firewall and restricted user rights? Or a VM to run this in?

Implying that both of these have been exploit free?

- posted from my totally secure Firefox

That is awesome

Go is the new C

C is the new C. Go is only going to replace C like Java was going to replace C.

C is hardly used in the enterprise space as it used to be in the 90's.

Even when C like performance is required, C++ is actually used instead.

The three major C compilers (gcc, clang and VC) are all written in C++ nowadays.

>>Java was going to replace C.

In the enterprise world Java did that - even high frequency trading applications have been Java based for quite some time. Compared to 20years ago, there is significantly less C code nowadays.

Reply on news.ycombinator.com