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A latency-hating emulator of 8- and 16-bit platforms: the Acorn Electron, Amstrad CPC, Apple II/II+/IIe and early Macintosh, Atari 2600 and ST, ColecoVision, Enterprise 64/128, Commodore Vic-20 and Amiga, MSX 1, Oric 1/Atmos, Sega Master System, Sinclair
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Thomas Harte 1237f174fe Merge pull request #216 from TomHarte/NoiseReduciton
Cleans up issues affecting the sleeper mechanism and the CPC
2017-08-20 13:26:56 -04:00
ClockReceiver Attempted to implement Sleeper in Drive and therefore in DiskController. Also corrected a couple of nonconformant file names. 2017-08-20 11:54:54 -04:00
Components Worked logic all the way down to the CPC. If the 8272 announces that it is asleep, it is now no longer clocked. Also very slightly cut down on IRQ line chatter to the Z80. 2017-08-20 12:05:00 -04:00
Concurrency Added an explicit nilling, to help with debugging. 2017-08-13 22:15:25 -04:00
Machines Quick fixes: the binary tape player now considers talk to the sleep observer only if motor control changes. The Amstrad CPC no longer attempts to use the component argument to identify the caller, since this will often be that of the superclass and not that of the derived class known to the CPC. 2017-08-20 13:18:46 -04:00
NumberTheory Fixed comments. 2017-08-11 20:22:14 -04:00
OSBindings/Mac Attempted to implement Sleeper in Drive and therefore in DiskController. Also corrected a couple of nonconformant file names. 2017-08-20 11:54:54 -04:00
Outputs Upped C++ standard to C++14 and added an #if that's intended to use the built-in std::gcd when compiled on C++17 or better. Fixed for new signedness warnings resulting for taking the step to C++14. 2017-08-11 19:18:45 -04:00
Processors Removed repeated checking of bus_request_line_. It's now checked only after each outward perform_machine_cycle. 2017-08-20 12:39:45 -04:00
READMEImages Adjusted brightness better to match its comparison. And to try partly to obscure its source. This isn't meant to be about software X versus software Y. 2017-08-16 21:04:09 -04:00
ROMImages Added the normal readme to explain what's omitted here. 2017-08-02 20:45:14 -04:00
SignalProcessing Completed curly bracket movement. 2017-03-26 14:34:47 -04:00
StaticAnalyser Added the base skeletal stuff of HFE support. 2017-08-17 21:48:48 -04:00
Storage Quick fixes: the binary tape player now considers talk to the sleep observer only if motor control changes. The Amstrad CPC no longer attempts to use the component argument to identify the caller, since this will often be that of the superclass and not that of the derived class known to the CPC. 2017-08-20 13:18:46 -04:00
.gitignore Added a new folder to the exclusion list, to contain commercial Atari images, to unit test my paging hardware selection logic. 2017-03-11 19:42:23 -05:00
.travis.yml It looks like spaces are automatically escaped (?) 2016-12-31 13:05:55 -05:00
LICENSE Initial commit 2015-07-16 19:46:52 -04:00
README.md Added a CPC grab, to show that it's not all about being composite. 2017-08-16 21:01:22 -04:00

CLK

CLK is an emulator for tourists that seeks best-in-class accuracy while minimising latency.

So its aims are:

  • single-click load of any piece of source media for any supported platform;
  • with a heavy signal processing tilt for accurate reproduction of original outputs;
  • that aims for the lowest possible latency; and
  • 100% accurate emulations, naturally.

It currently contains emulations of the:

  • Acorn Electron;
  • Amstrad CPC;
  • Atari 2600;
  • Commodore Vic-20 (and Commodore 1540/1);
  • Oric 1/Atmos; and
  • Sinclair ZX80/81.

Single-click Loading

Through the combination of static analysis and runtime analysis, CLK seeks to be able automatically to select and configure the appropriate machine to run any provided disk, tape or ROM; to issue any commands necessary to run the software contained on the disk, tape or ROM; and to provide accelerated loading where feasible.

The full process of loading a title — even if you've never used the emulated machine before — is therefore:

  1. locate it in your OS;
  2. double click it.

Signal Processing

Consider an ordinary, unmodified Commodore Vic-20. Its only video output is composite. Therefore the emulated machine's only video output is composite. In order to display the video output, your GPU then decodes composite video. Therefore all composite video artefacts are present and exactly correct, not because of a post hoc filter combining all the subjective effects that this author associates with composite video but because the real signal is really being processed.

Similar effort is put into audio generation. If the real machine normally generates audio at 192Khz then the emulator generates a 192Khz source signal and filters it down to whatever the host machine can output.

If your machine has a 4k monitor and a 96Khz audio output? Then you'll get a 4k rendering of a composite display and, assuming the emulated machine produces source audio at or above 96Khz, 96,000 individual distinct audio samples a second. Interlaced video also works and looks much as it always did on those machines that produce it.

Samples

1:1 Pixel Copying Composite Decoded
The Electron start screen, with a classic 1:1 pixel emulation The Electron start screen, decoded from an interlaced composite feed
Repton 3 in game, with a classic 1:1 pixel emulation Repton 3 in game, decoded from an interlaced composite feed
Stormlord with a classic 1:1 pixel emulation Stormlord decoded from an interlaced composite feed
1:1 Pixel Copying Correct Aspect Ratio, Filtered
Amstrad text, with a classic 1:1 pixel emulation Amstrad text, with correct aspect ratio and subject to a lowpass filter
Repton title screen, interlaced

Low Latency

The display produced is an emulated CRT, with phosphor decay. Therefore if you have a 140Hz monitor it can produce 140 distinct frames per second. Latency is dictated by the output hardware, not the emulated machine.

The machine update mechanism is influenced separately by both screen refresh and audio stream processing; audio latency is therefore generally restrained to 510ms regardless of your screen's refresh rate.

A corollary of emulating the continuous nature CRT, not merely performing end-of-frame transcriptions, is that the most common motion aliasing effects of displaying 50Hz video on a 60Hz display are minimised; you don't have to own niche equipment to benefit.

Accurate Emulation

Cycle-accurate emulation for the supported target machines is fairly trite now; this emulator seeks to follow that well-trodden path. All emulation logic is written in C++ for explicit control over costs but, where a conflict arises, the presumption is towards clarity and simplicity of code. This emulator is willing to spend the processing resources available on modern hardware.

Which are polite ways of saying that it's generally slower than the standard bearers for each supported platform but that if it's comfortably within the processing ability of a semi-modern computer then that's not considered problematic.