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+0:00:00.880,0:00:04.520
+hello everyone and welcome to my talk
+
+0:00:02.879,0:00:06.960
+state of retrogaming and emacs
+
+0:00:04.520,0:00:08.639
+[Music]
+
+0:00:06.960,0:00:12.000
+first of all a little bit about myself
+
+0:00:08.639,0:00:13.599
+my name is neilman i'm 28 years old
+
+0:00:12.000,0:00:15.200
+i work as a cyber security consultant
+
+0:00:13.599,0:00:17.440
+msg systems and
+
+0:00:15.200,0:00:19.359
+test other people's web applications and
+
+0:00:17.440,0:00:20.160
+review the source code for security
+
+0:00:19.359,0:00:22.960
+problems
+
+0:00:20.160,0:00:25.039
+you can reach me by email i have my own
+
+0:00:22.960,0:00:26.480
+self-hosted git repositories
+
+0:00:25.039,0:00:28.480
+and i have a blog where you can
+
+0:00:26.480,0:00:32.160
+occasionally find new posts by me on all
+
+0:00:28.480,0:00:34.800
+kinds of things not just emix things
+
+0:00:32.160,0:00:36.480
+so but the motivation about this one i
+
+0:00:34.800,0:00:38.079
+found that emacs is the ultimate
+
+0:00:36.480,0:00:40.160
+procrastination machine and there are
+
+0:00:38.079,0:00:41.200
+lots of fun demonstrations i'll go over
+
+0:00:40.160,0:00:44.160
+a few of them
+
+0:00:41.200,0:00:46.079
+for example someone made a thing to
+
+0:00:44.160,0:00:48.239
+order sell it for himself online so it
+
+0:00:46.079,0:00:50.879
+doesn't have to walk over to the shop
+
+0:00:48.239,0:00:51.760
+there's plenty rc bots there's some game
+
+0:00:50.879,0:00:53.520
+things
+
+0:00:51.760,0:00:55.600
+there's an emulator for the z machine
+
+0:00:53.520,0:00:57.600
+which you can use to play zorg
+
+0:00:55.600,0:00:59.039
+and so i asked myself at this point can
+
+0:00:57.600,0:01:01.039
+you actually emulate retro games at
+
+0:00:59.039,0:01:02.800
+60fps and it looked around a bit
+
+0:01:01.039,0:01:04.479
+and found some projects but none that
+
+0:01:02.800,0:01:07.360
+were actually able to
+
+0:01:04.479,0:01:08.000
+do it at 60fps so i set out to do my own
+
+0:01:07.360,0:01:09.439
+one
+
+0:01:08.000,0:01:11.119
+and looked out for a console that you
+
+0:01:09.439,0:01:13.439
+can actually emulate at that speed
+
+0:01:11.119,0:01:14.690
+using emax with its very very limited
+
+0:01:13.439,0:01:16.320
+rendering
+
+0:01:14.690,0:01:19.520
+[Music]
+
+0:01:16.320,0:01:20.560
+and here's the project chip8.el it's
+
+0:01:19.520,0:01:22.880
+pretty much finished
+
+0:01:20.560,0:01:24.000
+it clocks into under 1000 sourced lines
+
+0:01:22.880,0:01:26.159
+of code
+
+0:01:24.000,0:01:28.080
+it supports the superchip 8 extensions
+
+0:01:26.159,0:01:30.159
+it runs at full speed all games behave
+
+0:01:28.080,0:01:32.320
+okay as far as i'm concerned and
+
+0:01:30.159,0:01:34.479
+yeah i'm pretty happy with it it's very
+
+0:01:32.320,0:01:37.040
+much the hell world of emulation
+
+0:01:34.479,0:01:40.880
+and i might maybe do some other
+
+0:01:37.040,0:01:43.360
+emulation projects in the future
+
+0:01:40.880,0:01:45.439
+now for the section which is the longest
+
+0:01:43.360,0:01:46.320
+bunch of fun facts about ship a dot el
+
+0:01:45.439,0:01:49.759
+which i've learned
+
+0:01:46.320,0:01:52.240
+during this project so
+
+0:01:49.759,0:01:54.640
+what the hell is debate anyway first of
+
+0:01:52.240,0:01:56.799
+all unlike many other emulation game
+
+0:01:54.640,0:01:58.560
+things it's not a console but a vm
+
+0:01:56.799,0:02:00.000
+it was designed for easy parting of home
+
+0:01:58.560,0:02:02.560
+computer games
+
+0:02:00.000,0:02:03.680
+it wasn't terribly successful and but
+
+0:02:02.560,0:02:04.320
+there's still a small community of
+
+0:02:03.680,0:02:06.079
+enthusiasts
+
+0:02:04.320,0:02:09.119
+writing games for it and there are even
+
+0:02:06.079,0:02:11.920
+a few demos
+
+0:02:09.119,0:02:14.720
+this vm has system specs it has a very
+
+0:02:11.920,0:02:14.959
+very simple 8-bit cpu with 16 registers
+
+0:02:14.720,0:02:17.760
+and
+
+0:02:14.959,0:02:18.160
+36 fixed size instructions you have a
+
+0:02:17.760,0:02:20.560
+whole
+
+0:02:18.160,0:02:22.080
+4 kilobyte of ram you have a stack with
+
+0:02:20.560,0:02:24.480
+16 return addresses
+
+0:02:22.080,0:02:25.760
+the resolution is 64 by 32 black white
+
+0:02:24.480,0:02:28.000
+pixels
+
+0:02:25.760,0:02:29.440
+rendering is done by drawing sprites
+
+0:02:28.000,0:02:30.160
+these are drawn in excel mode meaning
+
+0:02:29.440,0:02:32.239
+that if you
+
+0:02:30.160,0:02:33.840
+draw a sprite and set a bit it just
+
+0:02:32.239,0:02:35.040
+flips over from black to white or white
+
+0:02:33.840,0:02:36.560
+to black
+
+0:02:35.040,0:02:38.239
+first one you have a modern buzz that
+
+0:02:36.560,0:02:40.640
+can just beep at one
+
+0:02:38.239,0:02:43.120
+frequency and most unusually there's a
+
+0:02:40.640,0:02:45.360
+hexadecimal keypad as input
+
+0:02:43.120,0:02:48.160
+so the keys are basically zero to nine
+
+0:02:45.360,0:02:48.160
+and a to f
+
+0:02:48.480,0:02:52.400
+so how does this whole thing work it
+
+0:02:50.879,0:02:53.599
+runs an unspecified speed
+
+0:02:52.400,0:02:54.879
+you'll probably have to do some fine
+
+0:02:53.599,0:02:56.080
+tune you find the speed you're happy
+
+0:02:54.879,0:02:58.560
+with
+
+0:02:56.080,0:03:01.120
+sound and delay timers exist they count
+
+0:02:58.560,0:03:02.879
+down at 60fps down to zero
+
+0:03:01.120,0:03:05.120
+this is done so that you can play a
+
+0:03:02.879,0:03:06.640
+sound at some specific time
+
+0:03:05.120,0:03:08.640
+the game itself is loaded with a fixed
+
+0:03:06.640,0:03:10.480
+offset into ram the program account is
+
+0:03:08.640,0:03:11.920
+set to exactly that offset
+
+0:03:10.480,0:03:13.840
+and from there it enters the game loop
+
+0:03:11.920,0:03:15.519
+where decodes and instruction executes
+
+0:03:13.840,0:03:18.130
+it for the side effects and just
+
+0:03:15.519,0:03:19.599
+loops and does this at infinitum
+
+0:03:18.130,0:03:21.920
+[Music]
+
+0:03:19.599,0:03:23.920
+so the game was the first thing where
+
+0:03:21.920,0:03:24.239
+into problems the usual game approach is
+
+0:03:23.920,0:03:26.640
+to
+
+0:03:24.239,0:03:28.239
+do stuff figure out how long to eight
+
+0:03:26.640,0:03:30.640
+wait for exactly that much and
+
+0:03:28.239,0:03:31.680
+repeat this doesn't work well in imax at
+
+0:03:30.640,0:03:34.959
+all because well
+
+0:03:31.680,0:03:37.280
+user input basically and
+
+0:03:34.959,0:03:39.040
+emacs is designed to just do whatever it
+
+0:03:37.280,0:03:40.080
+needs to do whenever you enter use input
+
+0:03:39.040,0:03:42.799
+instead of
+
+0:03:40.080,0:03:43.440
+doing things at one specific time if you
+
+0:03:42.799,0:03:45.040
+try to do
+
+0:03:43.440,0:03:46.640
+interruptable sleep well you get
+
+0:03:45.040,0:03:49.440
+unpredictable behavior
+
+0:03:46.640,0:03:50.959
+for example can be the timer doesn't run
+
+0:03:49.440,0:03:52.560
+at all at next time because you've
+
+0:03:50.959,0:03:54.400
+accidentally cancelled it
+
+0:03:52.560,0:03:55.760
+if you do uninterruptable sleep it's
+
+0:03:54.400,0:03:56.720
+freezes instead which isn't what you
+
+0:03:55.760,0:03:59.360
+want either
+
+0:03:56.720,0:04:00.560
+so i went for timers which forced me to
+
+0:03:59.360,0:04:02.159
+do inversion of control
+
+0:04:00.560,0:04:04.080
+meaning that i have to write code in the
+
+0:04:02.159,0:04:06.159
+style where it's just call it
+
+0:04:04.080,0:04:07.200
+time and this allows this input to
+
+0:04:06.159,0:04:09.120
+happen and to
+
+0:04:07.200,0:04:11.040
+for things to progress at roughly the
+
+0:04:09.120,0:04:12.879
+speed i want to
+
+0:04:11.040,0:04:14.159
+so there's the skydiver function which
+
+0:04:12.879,0:04:16.000
+is called a 60fps
+
+0:04:14.159,0:04:17.359
+and i have to be very careful to not do
+
+0:04:16.000,0:04:20.479
+too much in it
+
+0:04:17.359,0:04:22.960
+and say this function execute cpu cycles
+
+0:04:20.479,0:04:23.680
+decrypt the sound delay registers and
+
+0:04:22.960,0:04:27.759
+redraw
+
+0:04:23.680,0:04:28.800
+the screen so to map this whole system
+
+0:04:27.759,0:04:31.199
+to mx lisp
+
+0:04:28.800,0:04:33.120
+i've used just integers and vectors
+
+0:04:31.199,0:04:35.040
+which contain even more integers
+
+0:04:33.120,0:04:37.759
+this is used for the ram registers
+
+0:04:35.040,0:04:39.120
+return stack key state screen and so on
+
+0:04:37.759,0:04:41.520
+and so forth basically
+
+0:04:39.120,0:04:42.800
+what you would do if you were writing c
+
+0:04:41.520,0:04:44.560
+all of this is stored in global
+
+0:04:42.800,0:04:46.479
+variables i'm not using any
+
+0:04:44.560,0:04:48.400
+lists at all and as a side effect
+
+0:04:46.479,0:04:50.320
+there's no constant going on at all
+
+0:04:48.400,0:04:51.120
+there are no extra objects created which
+
+0:04:50.320,0:04:53.919
+would trigger
+
+0:04:51.120,0:04:55.840
+garbage collection pulses this getting
+
+0:04:53.919,0:04:56.720
+this red was rather tricky actually and
+
+0:04:55.840,0:04:58.560
+there were some
+
+0:04:56.720,0:05:01.680
+in garbage collection problems which i
+
+0:04:58.560,0:05:01.680
+had to resolve over time
+
+0:05:01.759,0:05:05.520
+so the coding instructions for this you
+
+0:05:04.320,0:05:06.800
+have to know that all instructions are
+
+0:05:05.520,0:05:08.880
+two bytes long
+
+0:05:06.800,0:05:10.240
+and the arguments encoded inside them
+
+0:05:08.880,0:05:11.440
+for example the jump to address
+
+0:05:10.240,0:05:15.120
+instruction
+
+0:05:11.440,0:05:18.400
+is encoded as one and three hex digits
+
+0:05:15.120,0:05:20.800
+the type is extracted masking with f000
+
+0:05:18.400,0:05:21.680
+and then shifting it by 12 bits mask
+
+0:05:20.800,0:05:24.000
+means the hd
+
+0:05:21.680,0:05:25.440
+performance binary end you can do the
+
+0:05:24.000,0:05:26.639
+same with the argument basement with
+
+0:05:25.440,0:05:29.520
+zero fff
+
+0:05:26.639,0:05:31.039
+and no shift if you do this long enough
+
+0:05:29.520,0:05:32.639
+you'll find common patterns for example
+
+0:05:31.039,0:05:35.280
+addresses are always encoded like this
+
+0:05:32.639,0:05:36.880
+using the last three nibbles in the code
+
+0:05:35.280,0:05:38.400
+you'll find a big count which dispatches
+
+0:05:36.880,0:05:40.070
+on the type and executes it for the side
+
+0:05:38.400,0:05:41.440
+effects
+
+0:05:40.070,0:05:43.440
+[Music]
+
+0:05:41.440,0:05:45.919
+for testing i've initially just accused
+
+0:05:43.440,0:05:47.280
+the rom until i fit ctrl g
+
+0:05:45.919,0:05:49.039
+and then use the debug command to run
+
+0:05:47.280,0:05:51.360
+the screen to a buffer
+
+0:05:49.039,0:05:52.320
+later on i found tiny roms that just
+
+0:05:51.360,0:05:55.680
+display a static
+
+0:05:52.320,0:05:57.280
+test screen for example logo and looked
+
+0:05:55.680,0:05:59.199
+whether it looked right
+
+0:05:57.280,0:06:00.960
+i added instructions as needed and went
+
+0:05:59.199,0:06:03.360
+through more and more and more roms and
+
+0:06:00.960,0:06:05.199
+later i wrote in unit test suite as a
+
+0:06:03.360,0:06:06.000
+safety net and this unit test suite it
+
+0:06:05.199,0:06:08.400
+just
+
+0:06:06.000,0:06:10.080
+sets up an empty emulator state executes
+
+0:06:08.400,0:06:10.400
+some instructions and then looks whether
+
+0:06:10.080,0:06:13.840
+the
+
+0:06:10.400,0:06:13.840
+expected side effects have happened
+
+0:06:14.880,0:06:19.120
+for debugging i usually use e-debug but
+
+0:06:17.120,0:06:20.880
+this was super ineffective because well
+
+0:06:19.120,0:06:22.960
+you don't really want to step through
+
+0:06:20.880,0:06:24.960
+big cons doing side effects for every
+
+0:06:22.960,0:06:26.880
+single cycle when it can take like 100
+
+0:06:24.960,0:06:29.680
+cycles for things to happen
+
+0:06:26.880,0:06:31.360
+therefore i've set up logging and
+
+0:06:29.680,0:06:32.720
+whenever i locked something
+
+0:06:31.360,0:06:33.919
+and couldn't figure out the error i
+
+0:06:32.720,0:06:37.039
+compared my lock output with
+
+0:06:33.919,0:06:39.199
+instrumented version of another emulator
+
+0:06:37.039,0:06:40.880
+and if the locks diverge then i have
+
+0:06:39.199,0:06:42.720
+figured out where the bug lies and could
+
+0:06:40.880,0:06:44.479
+look deeper into it
+
+0:06:42.720,0:06:46.639
+future project idea might be a chip 8
+
+0:06:44.479,0:06:50.720
+debugger but i doubt i'll ever
+
+0:06:46.639,0:06:52.639
+go into it for analysis i initially
+
+0:06:50.720,0:06:54.400
+wrote a disassembler which is a very
+
+0:06:52.639,0:06:56.160
+simple thing but super tedious
+
+0:06:54.400,0:06:57.599
+especially if you wanted to add advanced
+
+0:06:56.160,0:06:59.120
+functionality for example analysis or
+
+0:06:57.599,0:07:00.000
+thinking of what part is data what had
+
+0:06:59.120,0:07:01.840
+this code
+
+0:07:00.000,0:07:03.360
+and i had this great idea for using the
+
+0:07:01.840,0:07:05.120
+radari 2 framework
+
+0:07:03.360,0:07:06.479
+and adding analysis and disassembly
+
+0:07:05.120,0:07:08.400
+plug-in for it
+
+0:07:06.479,0:07:10.319
+so i looked into this found okay here
+
+0:07:08.400,0:07:12.160
+where you can write plugins in c
+
+0:07:10.319,0:07:13.520
+but also in python so i wrote one in
+
+0:07:12.160,0:07:15.039
+python and then the scout there's
+
+0:07:13.520,0:07:17.440
+actually existing one in core which you
+
+0:07:15.039,0:07:19.599
+have to enable explicitly by passing its
+
+0:07:17.440,0:07:21.840
+argument so i've tried it and found it's
+
+0:07:19.599,0:07:23.680
+not exactly as good as my own one so
+
+0:07:21.840,0:07:26.610
+improved this one and submitted pull
+
+0:07:23.680,0:07:28.080
+requests until it was at the same level
+
+0:07:26.610,0:07:30.160
+[Music]
+
+0:07:28.080,0:07:31.360
+rendering was the trickiest part of this
+
+0:07:30.160,0:07:34.319
+whole thing because
+
+0:07:31.360,0:07:35.759
+well i decided against using a library
+
+0:07:34.319,0:07:37.120
+not like there would have been any
+
+0:07:35.759,0:07:39.599
+usable library for this
+
+0:07:37.120,0:07:41.680
+my usual approach of accelerating svg
+
+0:07:39.599,0:07:45.120
+file was too expensive it just created
+
+0:07:41.680,0:07:47.360
+too much garbage and took too long time
+
+0:07:45.120,0:07:49.599
+i then tried creating mutating strings
+
+0:07:47.360,0:07:52.639
+this was either either too expensive
+
+0:07:49.599,0:07:55.039
+just like svgs or too complicated i
+
+0:07:52.639,0:07:57.280
+tried changing svg tiles which created
+
+0:07:55.039,0:07:59.520
+gaps between the lines
+
+0:07:57.280,0:08:00.720
+then i tried to create an xpm file which
+
+0:07:59.520,0:08:02.400
+was backed by a bull vector
+
+0:08:00.720,0:08:04.400
+administrating this bull vector
+
+0:08:02.400,0:08:06.879
+but the image caching effect made it
+
+0:08:04.400,0:08:10.000
+just every nth frame to appear which
+
+0:08:06.879,0:08:11.440
+wasn't good either then i had the idea
+
+0:08:10.000,0:08:13.280
+to just use plain text
+
+0:08:11.440,0:08:14.800
+and paint the individual characters with
+
+0:08:13.280,0:08:17.120
+a different background color this
+
+0:08:14.800,0:08:18.479
+this had perfect perfect performance
+
+0:08:17.120,0:08:20.000
+there were many optimization attempts
+
+0:08:18.479,0:08:21.840
+until i got there and it was
+
+0:08:20.000,0:08:23.199
+very very stressful i wasn't sure
+
+0:08:21.840,0:08:26.160
+whether i would ever get to accept the
+
+0:08:23.199,0:08:28.560
+performance at all
+
+0:08:26.160,0:08:30.319
+for sound you only need to a single beep
+
+0:08:28.560,0:08:31.280
+so technically it shouldn't be difficult
+
+0:08:30.319,0:08:33.519
+to emulate it
+
+0:08:31.280,0:08:34.880
+however doing this is hard because emacs
+
+0:08:33.519,0:08:37.200
+officially only supports synchronous
+
+0:08:34.880,0:08:39.039
+playback of sounds
+
+0:08:37.200,0:08:41.360
+but there's also emax process which you
+
+0:08:39.039,0:08:43.519
+can launch in asynchronous way
+
+0:08:41.360,0:08:45.279
+so i looked into it and found that
+
+0:08:43.519,0:08:46.640
+employee has a slave mode and mpv
+
+0:08:45.279,0:08:50.880
+supports listing on the
+
+0:08:46.640,0:08:54.000
+fifo for commands so i've created a pipe
+
+0:08:50.880,0:08:55.519
+started a past mpv in loop mode and
+
+0:08:54.000,0:08:58.000
+always send in pause and pause command
+
+0:08:55.519,0:09:01.839
+to the fifo and that way i could control
+
+0:08:58.000,0:09:01.839
+when to start beeping and stop beeping
+
+0:09:02.640,0:09:07.200
+so yeah that's it so far was a very
+
+0:09:05.760,0:09:09.279
+educational experience
+
+0:09:07.200,0:09:10.320
+i have tried out a bunch of games which
+
+0:09:09.279,0:09:12.640
+were
+
+0:09:10.320,0:09:14.320
+well i almost say the worst ports of
+
+0:09:12.640,0:09:15.839
+classic games i've ever tried
+
+0:09:14.320,0:09:18.320
+it wasn't terribly fun to play them but
+
+0:09:15.839,0:09:21.760
+was fun to improve the emulator until
+
+0:09:18.320,0:09:23.279
+well things worked good enough
+
+0:09:21.760,0:09:25.120
+and i've learned a lot about how
+
+0:09:23.279,0:09:27.760
+computers work at this level
+
+0:09:25.120,0:09:28.880
+so maybe maybe i'll in the future make
+
+0:09:27.760,0:09:31.920
+another emulator
+
+0:09:28.880,0:09:34.000
+but uh i'm not sure whether anything
+
+0:09:31.920,0:09:36.560
+more advanced like intel 8080 emulator
+
+0:09:34.000,0:09:37.839
+will actually run mix fast enough
+
+0:09:36.560,0:09:39.200
+but it's still an interesting idea
+
+0:09:37.839,0:09:39.600
+because then you could actually have an
+
+0:09:39.200,0:09:41.680
+os
+
+0:09:39.600,0:09:43.120
+inside emacs and fulfill that one
+
+0:09:41.680,0:09:45.440
+specific meme
+
+0:09:43.120,0:09:47.279
+but if i try to do most serious stuff
+
+0:09:45.440,0:09:48.000
+i'll probably use chicken scheme which
+
+0:09:47.279,0:09:49.920
+is my
+
+0:09:48.000,0:09:53.279
+preferred language for serious projects
+
+0:09:49.920,0:09:57.839
+and writing neso gamer emulator
+
+0:09:53.279,0:09:57.839
+and that's it thank you
+