Reading Silicon: How to Reverse Engineer Integrated Circuits

แชร์
ฝัง
  • เผยแพร่เมื่อ 20 พ.ค. 2024
  • Ken Shirriff has seen the insides of more integrated circuits than most people have seen bellybuttons. (This is an exaggeration.) But the point is, where we see a crazy jumble of circuitry, Ken sees a riddle to be solved, and he's got a method that guides him through the madness.
    In his talk at the 2016 Hackaday SuperConference, Ken stepped the audience through a number of famous chips, showing how he approaches them and how you could do the same if you wanted to, or needed to. Reading an IC from a photo is not for the faint of heart, but with a little perseverance, it can give you the keys to the kingdom. We're stoked that Ken shared his methods with us, and gave us some deeper insight into a handful of classic silicon, from the Z80 processor to the 555 timer and LM7805 voltage regulator, and beyond.
    Read the article:
    hackaday.com/?p=237161
    Learn more about Ken Shirriff:
    www.righto.com/
    Learn more about the Hackaday SuperConference:
    hackaday.io/superconference/
  • วิทยาศาสตร์และเทคโนโลยี

ความคิดเห็น • 357

  • @franklydude
    @franklydude 6 ปีที่แล้ว +444

    I'm a (retired) analogue IC designer and have many happy (?) memories studying other companies IC's using optical microscopes in our engineering laboratory, to reverse engineering them. It was a good way to learn tricks of the trade. I hope some engineers have studied some of my creations! We also used manual micro-manipulators to electrically probe connections when studying a powered up die. We sometimes used a laser to cut tracks in the lab. We also occasionally used an ion-beam milling machine to slice into the depth of an IC so we could modify the silicon experimentally. Oh what fun we had!

    • @willynebula6193
      @willynebula6193 6 ปีที่แล้ว +4

      Ion beam milling machine what a unique bit of gear! Something like that would have cost millions. What companies would even manufacturer a machine like that

    • @franklydude
      @franklydude 6 ปีที่แล้ว +29

      I forget the name of the company we used. It's not a big machine. Same principle as an electron beam microscope I think, although the polarity is obviously reversed! A tall evacuated chamber along which one accelerates charged particles. I think you have a very hot "anode" source creating a plasma (if that is the right terminology) so ions can be sucked away by the electric field. magnetic fields deflect the beam. The ions are much heavier than electrons and abrade the surface they hit... If I recall correctly, there was even technology to deposit material at a lower energy so that one could add a conducting track, very slowly......

    • @fakename3344
      @fakename3344 4 ปีที่แล้ว +1

      @@franklydude Would you happen to remember what it was? I'm really curious as to where I'd get the equipment to do this.

    • @franklydude
      @franklydude 4 ปีที่แล้ว +2

      @@fakename3344 I think it was companay in Cambridge or maybe even a university facility, I live in the UK... If you do a google for "focussed ion beam" milling etc, you should find some resources, certainly in the USA and in Europe, probably Japan and China too..

    • @gregorymalchuk272
      @gregorymalchuk272 4 ปีที่แล้ว +1

      @@franklydude
      Yeah, they also have ion implantation (basically ion doping) machines.

  • @HariWiguna
    @HariWiguna 7 ปีที่แล้ว +594

    I've always been impressed with those who could read disassembled code. but at minute 11:43 , Ken is disassembling SILICON and THEN disassembling the code that is in that ROM in that silicon! Oh as if that is not enough, he also wrote a simulator of the calculator he reverse engineered BY LOOKING AT THE SILICON!? WOW...

    • @HxcTufty
      @HxcTufty 6 ปีที่แล้ว +53

      Anyone that had being paying attention to EE classes (VLSI, Computer Archtecture, Microprocessors etc.) can do that. It is a lot of work though.

    • @dummypg6129
      @dummypg6129 6 ปีที่แล้ว +7

      Actually there is a method on how to perform that... Decap, hotspot, curve tracing etc. its just depending on the ic function/s thats varying and talent is required.

    • @Daniel-ib5bx
      @Daniel-ib5bx 6 ปีที่แล้ว +2

      I’m sayin right... what a bad ass lol

    • @zariumsheridan3488
      @zariumsheridan3488 6 ปีที่แล้ว +8

      what a royal waste of time though ...

    • @satibel
      @satibel 6 ปีที่แล้ว +47

      You are watching videos, what a waste of time!
      Jokes aside, any hobby may seem like a waste of time to others.

  • @TangodownNZ
    @TangodownNZ 4 ปีที่แล้ว +20

    I need the laser pointer when you zoom in please! Because we have no idea where he is pointing to.

  • @zlac
    @zlac 6 ปีที่แล้ว +344

    FFS, somebody give this guy a glass of water!

    • @meepk633
      @meepk633 6 ปีที่แล้ว +32

      Banana noises.

    • @Mx6D
      @Mx6D 6 ปีที่แล้ว +5

      so true lmao. Michael you hit right on the head

    • @crackmaster88
      @crackmaster88 6 ปีที่แล้ว +6

      hahah i thought i was the only one who noticed that :D :D

    • @Euquila
      @Euquila 6 ปีที่แล้ว +13

      it's like he's chewing on the very circuitry from his lecture.

    • @huckanz
      @huckanz 6 ปีที่แล้ว +2

      actually those dry-mouth sounds are so pleasant for me... weird...

  • @chiragsinghyadav
    @chiragsinghyadav ปีที่แล้ว +5

    I studied automation engineering and almost everything here was a part of the curriculum. I wish it was taught like this!
    Had so much difficulties in understanding the implementation of gates on chip that I couldn’t visualize it so had to learn them and I hated ‘just learning’ part. There’s no fun without seeing it practically. Great video

  • @samykamkar
    @samykamkar 6 ปีที่แล้ว +61

    Ken is awesome

    • @giuliaesposito3071
      @giuliaesposito3071 5 ปีที่แล้ว +1

      u too

    • @Adam-yd8dw
      @Adam-yd8dw 5 ปีที่แล้ว +1

      My hero ❤️

    • @rooster443
      @rooster443 5 ปีที่แล้ว

      Reverse engineering, the ultimate hacker skillz

    • @TracyNorrell
      @TracyNorrell 8 หลายเดือนก่อน

      If this the guy from the curious Marc videos?

  • @LumocolorARTnr1319
    @LumocolorARTnr1319 6 ปีที่แล้ว +84

    Good talk but what are they doing with the camera taking shots from the back of the room and switching to the talker when he is showing something on the screen. Whoever filmed and edited this, watch some defcon talks.

    • @michaelbuckers
      @michaelbuckers 4 ปีที่แล้ว +7

      Yeah the filming is abysmal. 95% of the time he's showing something with a laser pointer, you can't see what it is.

    • @josephmazzeo2713
      @josephmazzeo2713 3 ปีที่แล้ว +1

      I really wanted to see what he meant by the "oh that's bad..." slide.

    • @darrelldourte9455
      @darrelldourte9455 2 ปีที่แล้ว +1

      Couldn't watch...camera man destroyed all follow along to the educational value seeking to be given.
      Hand that man a broom.

  • @edinfific2576
    @edinfific2576 6 ปีที่แล้ว +3

    Very nice and interesting to see how those basic components and circuits are made. Great work!

  • @johnnyprimavera2
    @johnnyprimavera2 7 ปีที่แล้ว +3

    Simply put: Great overview of silicon features and excellent approach on chip decapping.

  • @dans.8198
    @dans.8198 6 ปีที่แล้ว +164

    Laser pointer vs mouse pointer :-(

    • @leocurious9919
      @leocurious9919 5 ปีที่แล้ว +32

      "this here..."
      "these ..."
      WHERE?!

  • @davidmaiolo
    @davidmaiolo 4 ปีที่แล้ว +1

    Thanks, had fun getting a better look into the transistor designs that actually make their way into an ic.

  • @AI6XG
    @AI6XG 3 ปีที่แล้ว +4

    Early Mostek calculator devices (1970s) had fake contacts that would mess with reverse engineering and swiping the circuit. The fake contacts were not able to be detected under optical microscopy unless you were good at noting the direction of focus

  • @Zemael
    @Zemael 6 ปีที่แล้ว +1

    Thank you! This is the kind of information I always tryed to find. Great links!

  • @jeremiefaucher-goulet3365
    @jeremiefaucher-goulet3365 4 ปีที่แล้ว +12

    If you guys like Ken Shirriff, I suggest watching the CuriousMarc channel. Ken is often there tagging along and working with the others in restoring and understanding these old computers.

    • @drdyna
      @drdyna 2 หลายเดือนก่อน

      That's where I knew the face from, haha. I was sitting here watching this dude like where have I seen him....watching Marc's space shuttle computer videos!

  • @NSAwatchesME
    @NSAwatchesME 7 ปีที่แล้ว +28

    i actually learnt quite a lot

  • @richardhead8264
    @richardhead8264 6 ปีที่แล้ว +11

    *_THAT_* was freaking cool!!!
    _So much better_ than textbook cartoons!

  • @fixing_stuff
    @fixing_stuff 9 หลายเดือนก่อน +1

    man you have to give the name of the music played at the end... so good

  • @MorganEarlJones
    @MorganEarlJones 6 ปีที่แล้ว +19

    I chuckled when I saw the instruction "waitno"

  • @kevinhevans
    @kevinhevans 5 ปีที่แล้ว +6

    Currently in school for comp E and we're slowly going over the topics presented, so this talk is really fascinating (to see this stuff in practice!)
    Does anybody know how large were the teams that were designing these chips?

  • @whiteburr
    @whiteburr 5 ปีที่แล้ว +8

    Phenomenal presentation! I want to thank that guy (and get him a bottle of water!)

  • @Stallnig
    @Stallnig 6 ปีที่แล้ว

    crazy how much stuff is on these tiny pieces, and its getting even crazier by the day. I can't even imagine how much engineering hours and knowlege went into any of these things.

  • @Cyberfoxxy
    @Cyberfoxxy 5 ปีที่แล้ว +4

    after a decades of innovation we still haven't figured out how to get a laser pointer on youtube

  • @EnglishTeacherBerlin
    @EnglishTeacherBerlin 6 ปีที่แล้ว +1

    Absolutely fascinating! Thanks a lot!

  • @iuliannitu5699
    @iuliannitu5699 5 ปีที่แล้ว +1

    Very interesting what you do Ken. Thank You.

  • @12volt15
    @12volt15 2 ปีที่แล้ว +1

    Thank for sharing this! Really appreciate it!

  • @jlg23us
    @jlg23us 7 ปีที่แล้ว +2

    Great job! Thank you for sharing :D

  • @SerBallister
    @SerBallister 2 ปีที่แล้ว

    Fascinating talk, learned a few things new things it. Thank you so much.

  • @mrroobarb
    @mrroobarb 6 ปีที่แล้ว

    Fantastic - very informative.

  • @PauloConstantino167
    @PauloConstantino167 4 ปีที่แล้ว

    Beautiful work.

  • @nxxxxzn
    @nxxxxzn 7 ปีที่แล้ว +1

    this channel is awesome

  • @tmdrake
    @tmdrake 5 ปีที่แล้ว +2

    Rawr, Love the chip die art!

  • @yoramstein
    @yoramstein 7 ปีที่แล้ว

    Great lecture

  • @willynebula6193
    @willynebula6193 7 ปีที่แล้ว

    absolutely brilliant

  • @sjb27182
    @sjb27182 6 ปีที่แล้ว

    Silicon in an elevated enthalpy reaction(add heat) undergoes an elevation of the 3p orbitol, allowing for an enthalpy controlled reduction/oxidation reaction of the atom. So start there. Then make transistors...

  • @danielkrajnik3817
    @danielkrajnik3817 3 ปีที่แล้ว

    this is crazy, awesome, breathtaking

  • @sardinefinder334
    @sardinefinder334 4 ปีที่แล้ว +2

    My digital logic professor brought me here. THANKS J DAWG

  • @DavidvanDeijk
    @DavidvanDeijk 4 ปีที่แล้ว +1

    2nd time i watch this, still wrecking my brain about that ALU trick.

  • @hereb4theend
    @hereb4theend 3 ปีที่แล้ว

    Absolutely brilliant. Thank you very much.

  • @MadsonOnTheWeb
    @MadsonOnTheWeb 4 ปีที่แล้ว +1

    It could've been even longer presentation and I still would watch it.

  • @dkaye512
    @dkaye512 6 ปีที่แล้ว +15

    If you have an archive of the raw footage from all of the cameras, it would greatly helpful to have the wide angle shot showing you pointing is really helpful. However, the slides are better resolution, but where he is pointing is lost. The lecture is very interesting, but when you don't see where he is pointing makes much more difficult to follow Thanks.

    • @edgeeffect
      @edgeeffect 4 ปีที่แล้ว

      Yeah you can't win with the slides... laser pointer OR better quality image but you can't have both.... ideally we need speakers to use some kind of "virtual laser pointer" on the presentation laptop.

    • @olegil2
      @olegil2 2 ปีที่แล้ว

      @@edgeeffect You can have both, it's called picture in picture. You can show slide, presenter and picture of where he's pointing at the same time. Then the virtual experience would in most cases actually be better than the real one.
      "Virtual laser pointer" as in mouse pointer? Yeah, would be nice if someone invented that.

  • @tekvax01
    @tekvax01 4 ปีที่แล้ว +1

    where did the cool opening and closing music come from? anyone know who made it?

  • @damianbutterworth2434
    @damianbutterworth2434 ปีที่แล้ว

    I have a David and Mann x,y table from a microchip factory. Very accurate. It had a 110 volt motor on the x axis. So I wonder if it was for cutting the wafers up.

  • @bkzzzzz
    @bkzzzzz 6 ปีที่แล้ว

    very nice inside of very popular chips. I always wonder how do they work still so tinny.

  • @harakatabdelmjid9449
    @harakatabdelmjid9449 4 ปีที่แล้ว +1

    Merci pour la vidéo j'aime beaucoup les recherches

    • @ismaillafria2757
      @ismaillafria2757 4 ปีที่แล้ว

      كتبغيو البحث ولا كيعجبكم غير تشوفو الأخرين كيقومو بأمور خارقة بحال هكا,,العربان أش عندكم ماديرو

  • @TSulemanW
    @TSulemanW 2 ปีที่แล้ว

    Nice explaination

  • @amrkoptan4041
    @amrkoptan4041 6 ปีที่แล้ว

    im a big fan of yours since curious marc channel !!!!

  • @PilotPlater
    @PilotPlater 6 ปีที่แล้ว

    MikesElectricStuff does videos deencapsulating chips which is cool, but havent seen or forgot ever seeing anyone show a transistor-level look! Cool

  • @jaymzkardell1841
    @jaymzkardell1841 7 ปีที่แล้ว

    This is awesome.

  • @abdokamal4133
    @abdokamal4133 ปีที่แล้ว

    Thank you. I wanted to ask about the power of the microscope used

  • @linuxguy1199
    @linuxguy1199 6 ปีที่แล้ว +57

    28:30 Looks more like a factorio base than an IC XD

    • @PilotPlater
      @PilotPlater 6 ปีที่แล้ว +2

      this made me chuckle

    • @DavidHenderson1
      @DavidHenderson1 4 ปีที่แล้ว +1

      I mean, in a way, they're essentially the same thing. With Factorio, you're taking resources and converting them into other resources. With processors you're taking inputs and converting them into outputs.

  • @hqqns
    @hqqns 4 ปีที่แล้ว +3

    Oh, it's Ken from Marc's channel!

  • @MrGunnaras
    @MrGunnaras 5 ปีที่แล้ว

    You are amazing!

  • @xenlase
    @xenlase 7 ปีที่แล้ว +15

    Brilliant :)

    • @nagualdesign
      @nagualdesign 6 ปีที่แล้ว

      My sentiments exactly.

  • @NicksStuff
    @NicksStuff 29 วันที่ผ่านมา

    This blew my mind

  • @peterhindes56
    @peterhindes56 6 ปีที่แล้ว +15

    shame I cant see the lazer pointer

  • @neojb7417
    @neojb7417 6 ปีที่แล้ว +1

    YES!

  • @delysid111
    @delysid111 2 ปีที่แล้ว

    His good . the true beauty of transistors is the differance in opening, and closing . Some are Voltage controlled, some are Ampere controlled, some are Normally Open NO, others are NC, Normally Closed , before you apply voltage to them . NPN & PNP junctions .

  • @HansBaier
    @HansBaier 3 ปีที่แล้ว

    Excellent!

  • @jamest.5001
    @jamest.5001 6 ปีที่แล้ว +10

    I don't think I'd wanna buy a POSFET OR a POS transistor. this is a very interesting video.

    • @tibfulv
      @tibfulv 5 ปีที่แล้ว +3

      How about an old SGI Tezro? SGI doesn't exist anymore, and to our knowledge these machines aren't repairable using standard services. Reengineering the ICs may be the only way to service them, and emulation requires the same thing.

  • @emmarobertson3933
    @emmarobertson3933 4 ปีที่แล้ว

    9:02 just for efficiency, would it not be better to use just 2 transistors to solve the NOR circuit
    the 3 transistor seems of no use theoretical it might be part of the drawment for the negation but why would you do that then

  • @-LightningRod-
    @-LightningRod- 5 ปีที่แล้ว +3

    bro, u r amazing, that is soo cool
    ,nd the earth is burning,

  • @PauloSantos-cv1bi
    @PauloSantos-cv1bi 4 ปีที่แล้ว

    Wow! Amazing!!

  • @generosonunezarias369
    @generosonunezarias369 3 ปีที่แล้ว

    This Guy is a Beast with Silicon! Wow!

  • @WooShell
    @WooShell 6 ปีที่แล้ว +1

    Who's the end theme song from? I need that track badly..

  • @josephmazzeo2713
    @josephmazzeo2713 3 ปีที่แล้ว

    I always wondered if a working chip with a metal lid will continue to work with the lid popped off and exposed to ambient air. The lid would have to be removed carefully so as not to damage the bonding wires or the chip. Would light have any effect? How about a low power laser such as from a pointer? EPROMs continue to work even though the window is exposed (although erasure might occur after some time), so I guess yes?

    • @KevinJohnson-fw8kv
      @KevinJohnson-fw8kv ปีที่แล้ว

      it has to be exposed to UV light a strong UV light. Which is why some of these EEPROMs that are being pulled out of vintage computers from the 80's still have all of their EEPROM data intact.

  • @BemBem-G
    @BemBem-G 6 ปีที่แล้ว

    hay quá. cám ơn rất nhiều. rất hữu ích. tôi rất thích chúng.

  • @ajikishaya463
    @ajikishaya463 ปีที่แล้ว

    I've been wondering how the control logic schematic looks like and how it interacts with the interrupts in the instruction rom( schematic) at transistor leve of the z80 and it's burning my neural circuit. Someone plz save me!

  • @paulgill7222
    @paulgill7222 ปีที่แล้ว

    Guys like him and the designers are out of this world, seriously extra terrestrial ufos.....wow.... way over my head..........

  • @deaustin4018
    @deaustin4018 5 ปีที่แล้ว

    well, I started programming in the late 60s, but I can still understand like maybe up to 30 percent of this. I checked with a couple other people, sure enough, they couldn't understand a single word, so I'm happy enough.

  • @gregorymccoy6797
    @gregorymccoy6797 2 ปีที่แล้ว

    It's Master Ken!!!

  • @climbeverest
    @climbeverest 3 ปีที่แล้ว +1

    Incredible only in America such geniuses self develop

  • @nicknicolosi1
    @nicknicolosi1 6 ปีที่แล้ว

    that's impressive!

  • @NorthWay_no
    @NorthWay_no 4 ปีที่แล้ว

    Fantastic stuff. Is there anything like a program that can be fed a die photo and more or less make sense of it?

    • @snooks5607
      @snooks5607 3 ปีที่แล้ว

      that's how you create Skynet

  • @metallitech
    @metallitech 6 ปีที่แล้ว +1

    When I was 11 or 12 years old I did a science fair thing where I got the chips out and let people look at them with a microscope. The way I came up with for getting the silicon out was simply by heating the package until it crumbled.

  • @aaronr.9644
    @aaronr.9644 7 ปีที่แล้ว

    Great stuff! Is there a forum somewhere (something like reddit) where ppl take a stab at analysing these die pics?

  • @limsheng4873
    @limsheng4873 5 ปีที่แล้ว

    we should b extremely thankful 4da existence of XEROX ALTO cuz it was a precursor 2all modern Pc's.

  • @abbyboing
    @abbyboing 4 ปีที่แล้ว +2

    Excellent amount of information. Respect. Just the Saliva sound was a bit bothersome. Sounded a bit kinky while under the impression of knowledge. You know.

  • @terencem9962
    @terencem9962 6 ปีที่แล้ว

    i got a few chips open but it just was white mush. don't know where they put the transistors and i have a feeling they had just stuffed it with potatoe

  • @EllotusFreeholy
    @EllotusFreeholy 6 ปีที่แล้ว +25

    "if you stare at it long enough it will start to make sense" ~ No, if YOU stare at it long enough it will start to make sense, if I stare at it long enough i'll get a headache. lol

    • @firmman4505
      @firmman4505 4 ปีที่แล้ว

      Ellotus Freeholy lol

  • @Bianchi77
    @Bianchi77 4 หลายเดือนก่อน

    Cool video, thanks :)

  • @Sparkette
    @Sparkette 4 ปีที่แล้ว +1

    Am I the only one who saw "Instruction ROM" in the calculator chip and immediately thought, I'd love to experiment with that and see what changing values in it would do?

  • @seankayll9017
    @seankayll9017 6 ปีที่แล้ว +1

    You sounded really nervous. Relax, it was a fascinating talk and your presentation was excellent.

  • @StefanReich
    @StefanReich 5 ปีที่แล้ว

    Love it

  • @arts9591
    @arts9591 6 ปีที่แล้ว

    ALU the real brain of a chip by Ken.S

  • @n.aminr.7175
    @n.aminr.7175 4 ปีที่แล้ว

    For YT videos, I suggest you show the diagram next to the actual screen. I can't see that laser dot on my screen to sync with his explanation lol.

  • @Donatellangelo
    @Donatellangelo 7 ปีที่แล้ว

    This looks like it takes a lot of patience. But that's okay, well worth it in the end.

  • @Kenbomp
    @Kenbomp 3 ปีที่แล้ว

    Not unusual cur mirror it saves allot of space. Beautiful design

  • @jeffsheldon
    @jeffsheldon 7 ปีที่แล้ว

    I've found that very flat ceramic chips (which can't be chiseled) can be heated and will crumble, though occasionally with case residue on the die. The fumes are not good for breathing.

    • @andreassjoberg3145
      @andreassjoberg3145 5 ปีที่แล้ว

      I think that we soon will have access to high power laser beams that can chisel away AND scan a chip in 3D and remodel them, as a by-product of the nascent 3D-printing technology.

  • @SebastianGarcia-go4tx
    @SebastianGarcia-go4tx 3 ปีที่แล้ว +1

    This guy should definitely write a book about this topic. I'd love to learn more about it.

  • @bluestar2253
    @bluestar2253 3 ปีที่แล้ว +2

    Anybody here still remember the early days of 1980s when the Soviets stole the blueprint for Zilog Z8000 microprocessor and tried to reverse engineer it.

    • @johnmarks714
      @johnmarks714 2 ปีที่แล้ว

      I dont. Got any info? Im interested

  • @MarkSeve
    @MarkSeve 6 ปีที่แล้ว

    PoW!! Mind blown! Additionally, watch Ben Eater for step 2

  • @raynegames2636
    @raynegames2636 6 ปีที่แล้ว

    This Guy is a master of the modern reverse Engineering, a God...

    • @choosetolivefree
      @choosetolivefree 6 ปีที่แล้ว +1

      These chips are not modern, but in fact very old. This would be nearly impossible to do with modern chips, as one of the commenters above explained very well

  • @edgeeffect
    @edgeeffect 5 ปีที่แล้ว +2

    Oh hello Ken! Seen you before hanging around with Curious Marc.

    • @hqqns
      @hqqns 4 ปีที่แล้ว +3

      It was a pleasant surprise to recognise someone. He definitely is a reverse engineering king.

  • @guilldea
    @guilldea 3 ปีที่แล้ว

    master Ken

  • @nawasmajeed5493
    @nawasmajeed5493 ปีที่แล้ว

    thanks

  • @peterbonnema8913
    @peterbonnema8913 4 ปีที่แล้ว

    Is that a factorio megabase???

  • @RequiemForABuckeye
    @RequiemForABuckeye 2 หลายเดือนก่อน +1

    It'd be nice if we could actually see what he's pointing at when he keeps saying which parts "run here"

  • @haxxx0rz
    @haxxx0rz 5 ปีที่แล้ว +3

    Nice outro music. Sounds very 303-ish :-)

  • @spidermcgavenport8767
    @spidermcgavenport8767 5 ปีที่แล้ว

    My favorite past time hobby is editing assembly code in original Nintendo games. Hex editor for DOS. Keeps me busy.

  • @noreagatube
    @noreagatube 3 ปีที่แล้ว

    nice!