91 thoughts on “8-bit CPU reset circuit and power supply tips

  • May 29, 2017 at 6:48 pm
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    Jameco offers breadboards with a 1 year warranty. I'm waiting for a pack of them because the Elegoo ones I got off Amazon were total crap. Dip Switches won't stick in them at all, tactile switches barely stay in… plus the same problems you show with the cheap one here. I've made some progress on my Brainfuck CPU but the breadboards can cause some real problems if you skimp.

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  • May 29, 2017 at 7:01 pm
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    Why do we even use the 5th step reset? If we want to add more microinstruction it will get quite complicated.

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  • May 29, 2017 at 7:01 pm
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    what is the fastes you can run de cpu? can you try it

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  • May 29, 2017 at 8:04 pm
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    Thanks for the tips. I use the lower cost breadboards for my own build (a computer that also does video, see my videos). I bought these because you need so many of them. I can confirm that the insert can be difficult. Once you understand how the pins work internally, you know what is happening. They are not always well-aligned underneath the hole, and the mouth or funnel is not as good. There are videos that tear them open and compare. Just don't force them, wiggle a lot, and it should be fine.

    I believe I have forgotten about the power rail gap many times already, very annoying. I suppose they are intended so you can do different projects. But bridging them also causes an unnecessary additional resistance.

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  • May 29, 2017 at 8:48 pm
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    You probably got this question a few times now, but how are you making these cables? Are you building the episode beforehand, destroy it and use the cables from bevore?

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  • May 29, 2017 at 8:51 pm
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    can you add an IO module, to see how the computer interact with the outside world. keep the good work ^^

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  • May 29, 2017 at 9:03 pm
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    Can someone pls explain me how to 9V to 5V??? I use icgates and ofc LEDs but i Dont want to destroy my Circuits… :c PLS HELP!

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  • May 29, 2017 at 9:06 pm
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    Big thanks for this great work and effort and good explanation.

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  • May 29, 2017 at 9:29 pm
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    108 Leds and only 8 have resistors? I see some potential for a power cutdown 😉

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  • May 29, 2017 at 9:34 pm
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    Can't we use the non inverted reset, before the first nand gate?

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  • May 29, 2017 at 9:54 pm
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    Hi, I love this series, and am probably going to build one for myself. Maybe you could add some sort of "jump if" op code to the computer, so you can do slightly more complex programs.

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  • May 29, 2017 at 10:18 pm
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    Ben, could you please implement a micro instruction counter reset whajingey to avoid wasted micro cycles, just so people will shut up in the comments? Thank you. / All of us who have to read the comments.

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  • May 29, 2017 at 10:55 pm
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    Y U no JMP

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  • May 29, 2017 at 11:03 pm
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    Have you had any problems not using smoothing capacitors on the TTL chips? Mine was behaving very wonky until I started putting capacitors on all the chips.

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  • May 30, 2017 at 12:54 am
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    I can't wait for the next chapter, I don't have idea what next but allways something excelent and with an perfect explanation. Maybe the next step could be to add more instructions but I think is time to make a new programming system, maybe with a keypad.

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  • May 30, 2017 at 2:16 am
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    I have no idea what's going on is there like a beginning to this where you explain everything

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  • May 30, 2017 at 3:16 am
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    It is totally amazing that something half that complex is running on a breadboard!

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  • May 30, 2017 at 4:29 am
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    Thank you very much, I always learn something from your videos.

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  • May 30, 2017 at 4:30 am
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    Are you guys aware of any File system tutorial like the way,it was explained here

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  • May 30, 2017 at 5:22 am
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    this is beautiful

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  • May 30, 2017 at 6:31 am
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    upgrade the alu so that it can also perform AND, OR and NOT operations …

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  • May 30, 2017 at 7:24 am
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    I wonder what the outcome of his computer will be

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  • May 30, 2017 at 8:02 am
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    Thanks again for the slow pace and the detailed explanations, Ben! Regarding breadboards, I've got exactly the same cheap brand, for less than 2€ a piece. They are a bit difficult to use, but they don't have upside-down numbers or split power rails on them – I guess yours are even cheaper copies of a cheap model. The cheapness of the boards can be a bit annoying, but once your components are placed it's not an issue anymore. – And now for something completely different, I saw someone else solder all their power connections together, using pinheaders for each breadboard connection. Anyway, thanks again, I'm looking forward to the jump circuit! =)

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  • May 30, 2017 at 8:36 am
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    It's interesting that the MB-102 boards you received are the low-quality boards with breaks in the middle, because the latest boards I purchased are exactly the same brand and even came in exactly the same package with exactly the same brand markings, but they're better quality than the ones you're showing and with continuous power rails and more consistent printing (although the numbers are still not quite aligned properly).

    The boards I got still aren't the best quality, but they're acceptable if you're willing to overlook their shortcomings.

    I posted a link to the eBay listing on a previous video. The seller offers boards, a power supply plugin board and jumper cables, and offers them in a few combinations too.

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  • May 30, 2017 at 10:35 am
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    It's been fun watching your videos Ben Eater. Keep it up!

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  • May 30, 2017 at 11:26 am
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    Do you have a jig or method for making your small jumpers. Or have you just made enough for muscle memory to kick in.

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  • May 30, 2017 at 1:13 pm
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    Ben thank you for the series. This is one of my favorites on YouTube. Next installment, boot monitor, GPIO, I2C, keypad w/hardware & software…? I guess I am getting nostalgic about my old KIM II SBC. The advice about breadboards is very helpful, especially when buying them online. I have noticed a huge difference in quality and spent a lot of time troubleshooting issues that ultimately were not my design or programming, but rather flaky connections (especially with signals that have critical timing).

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  • May 30, 2017 at 7:34 pm
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    As usual, great work!

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  • May 30, 2017 at 10:33 pm
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    I've made CPUs in FPGAs before, but my instruction decoders were done in a case block and the micro code was also done in a descriptor language.

    After watching these videos, I want to try this with the schematic designer with nothing but gate logic, no IP cores except for the M9K blocks.

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  • May 30, 2017 at 10:55 pm
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    That dip switching speed tho

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  • May 31, 2017 at 10:40 am
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    Excellent! Also – a note on the cheap MB-102s – there may be two 'flavours' of them, one packaged with a black top (which has the weird numbering, the power rail breaks, the reverse printing, the difficult insertion) and one packaged with a blue top (which has none of these issues).

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  • May 31, 2017 at 2:37 pm
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    Should consider adding some sort of card-reader so it becomes easier to program the machine. 🙂

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  • May 31, 2017 at 2:42 pm
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    thank you sir your videos made me clear my doubts about the microprocessor and microcontrollers.

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  • May 31, 2017 at 9:01 pm
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    In the beginning of this series, you talked about decoupling. Perhaps that would add stability too. All those millisecond breaks-makes from wiggling the power feed connector would be "filled in" by extra capacitance. Plus it'd serve its usual role of making sure the chips don't glitch due to action of the other chips.

    I was wondering…with these EEPROMs, have you in essence been using the equivalent of an FPGA; is that the sort of thing FPGAs are for?

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  • June 1, 2017 at 2:14 am
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    You should really add I/O to you computer because then you could use it to run LEDs or motors.

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  • June 1, 2017 at 2:45 am
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    I wish you some day write a book how to build 8 bit computer from scratch

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  • June 3, 2017 at 9:44 am
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    I'm currently reproducing the control logic counter in my build. I hooked up the green LEDs driven by the 138 to 5v, not ground, so only one of them is active and i presumably save a few milliamps. This also makes more sence to indicate on which step the computer is.

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  • June 4, 2017 at 3:19 am
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    I was just wondering. Why did you not use current limiting resistors with all of the leds instead of just some of them (i.e.the blue Control Signal leds)?

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  • June 4, 2017 at 11:30 pm
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    Hello Ben, LoneRegister,

    Just watched LoneRegister Micro Code Reset Circuit video, My two bits.

    I am going to try coding my EEPROM using the 16th open instruction decoder output pin as an "Instruction Micro Code Step Counter Reset" signal so your final Micro Code step instruction will reset the Micro Code counter to eliminate wasted instruction T Cycles.

    Remember NOP is 00

    Keep up the good work 🙂

    Thanks, Mike DeLosier

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  • June 6, 2017 at 3:18 am
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    Great Ben

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  • June 7, 2017 at 4:29 pm
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    Where are the JMP (Jump) and JIF (Jump If Carry) instructions?

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  • June 8, 2017 at 8:44 am
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    Sorry man I can't afford to be your pateron because i am a kid. But i swear when i earn money I'l firstly donate it to you. Thanks for giving us details on those computers, helped me a lot.

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  • June 10, 2017 at 3:27 pm
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    Have you ever thought about adding some sort of serial connection to it, so you could 'control' it from your computer? After jmp/etc is implemented of course, but it would be neat to make it do a simple game, or 2+8=whatever somewhere other than hardcoding it in

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  • June 12, 2017 at 9:42 am
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    you inspired me to build a breadboard computer that runs BrainFuck (I swear, it's the name of the coding language)

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  • June 14, 2017 at 10:58 am
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    Awesome series, I've been slowly building my own version of this with some changes including adding a 1Mhz clock circuit and using solderable boards and IDC cables etc, still waiting on the memory chips and a supply of EEPROMs that will actually program on my eprom burner, some used ones I got off eBay have bad cells and I put in a request to get more with a local supplier which seemed to work. I am wondering if you will eventually release a binary dump of the EEPROMs, the display one I managed to modify the arduino program and dump out into a bin file the microcode might be more of a challenge.

    So far I have completed and tested the clock, PC and output, and ALU and I'm in the process of wiring the IR and control board, which leaves just the memory once I get the RAM chips

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  • June 15, 2017 at 7:57 pm
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    are you going to make more videos upgrading this computer?

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  • June 19, 2017 at 3:22 pm
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    Thank you for these fantastic videos. I am an electrical contractor, built many control panels etc and spent many years as a kid writing basic programs for the C64 and the BBC micro. Never managed to really blur these lines and understand electronics and the basic principals of how computers work. Until now. I plan to order the bits and probably build this on boards and put in a nice case with lots of flashing lights and switches on the front 🙂 Thanks again for your fantastic work.

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  • June 19, 2017 at 4:22 pm
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    I built the computer almost finished, just the Control module is missing. Unfortunately i have to say that i am about to give up on this project. The power issues i have are just not managble for me. Each module on its own works fine, but after i plugged all together there is always at least one module that is not working correctly, that is not taking values from the bus or not put values on the bus. sometimes i also just lightly tap on the table which already sametimes causes some LEDs to toggle on and off… I used some mid range Breadboards, but i think for this kind of big problems it is unavoidable to invest into the really expensive breadboards.
    I also wonder if my power plug might be too weak, it is rated for 1A, but when i measure the total vurrent i only get 0.45A, which seams to be to low comapred to bens values. Maybe i also should try a better power adaptor.
    Anyways, i am really frustrated about this project, because i theory it would work great for me since every module works fine alone, but then the reality hits me when i try to put stuf together.

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  • June 28, 2017 at 4:57 pm
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    if you used 100kΩ pulldown resistors instead of 10kΩ on your switches, would you would reduce pulldown leaking power by 10fold?

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  • July 2, 2017 at 2:46 pm
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    how do you make the wires so perfectly

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  • July 3, 2017 at 8:54 pm
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    Thank you for a great series! It was very interresting.

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  • July 6, 2017 at 9:21 am
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    I always wondered why the first vacuum tube based computers had so many lights. Now I understand.

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  • August 5, 2017 at 11:21 pm
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    You show but say nothing about the data lines being shorted on your 2 A charger. Its critical. Without that, 500 mA is what you get.

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  • September 15, 2017 at 6:19 pm
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    thank you so much Ben..great video

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  • November 18, 2017 at 4:57 am
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    Can u suggest other channel like yours…urs is great by the way

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  • November 19, 2017 at 10:12 pm
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    Guess I'm gonna have to wait another week to finish this since the parts list said only one 74LS00 🙁
    Edit: you can replace the 00 with an AND and NOT chip 😉

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  • December 20, 2017 at 8:11 pm
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    Hey .. very delightful work keep going :)…. and I have questions please …. I have 7400 and ,or, xor,nad and I wanna connect the output of a gate to another gate input but when I tried to do so nothing work please can you tell why?

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  • December 22, 2017 at 5:48 am
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    Can't stop watching!

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  • February 9, 2018 at 12:59 pm
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    How come that some LEDs don't need resistors?

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  • April 13, 2018 at 11:05 pm
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    Excellent Instructions. Keep up the Good Work!

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  • April 14, 2018 at 8:46 am
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    Great videos,
    BUT as to your power supply issues, You should have notices it when you were testing with the multimeter.
    It was reading 4.7 volts which is under rated. Keep up the good work.

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  • May 3, 2018 at 9:08 am
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    Hey Ben Eater, you could try and add another 555 timer and PWM the leds and cut power consum in half, depending on the frequency by the 555 timer.

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  • May 13, 2018 at 7:11 am
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    I ordered a MB-102 breadboard and it was just like the BB830. There wasn't a break in the power lines and the printing of the letters and numbers was accurate and not flipped on the opposite end. It also had good connections. So they have either improved there breadboards, or i was sent a better breadboard in MB-102 packaging.

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  • June 9, 2018 at 7:46 pm
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    This was a great journey. I enjoyed every bit of it. Thanks for putting all things togeter in a consistent way, so it was easy to folow through. Good luck with other projects.

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  • July 5, 2018 at 10:08 pm
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    it running at full speed the stopping makes me the happiest person on the planet

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  • July 5, 2018 at 10:16 pm
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    i think you need a current direction thingy in there somewhere (at 9:00)

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  • August 17, 2018 at 7:42 pm
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    one big calculator 😀

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  • August 22, 2018 at 4:42 pm
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    I like it, to watch you messing around with this computer.

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  • September 29, 2018 at 3:08 pm
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    Does it actually calculate numbers? Does it have interface to type numbers? And i think you need to use Arduino to reprogram it without disconnecting ROM chip

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  • September 30, 2018 at 6:15 pm
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    NOW can it run Crysis?

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  • November 5, 2018 at 9:44 pm
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    Regarding the power supply: I have found that these are well worth the cost. http://a.co/d/4rpranQ
    They allow you to select 5v or 3.3v on either rail while still providing for jumper connections for each voltage level.

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  • November 7, 2018 at 1:28 am
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    After hooking up the reset signal to the program counter and removing the permanent wire to ground on the master reset on the chip my program counter acts weird and resets after a few counts. Ideas?

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  • January 2, 2019 at 4:52 pm
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    Try adding a register for memory banking, and increasing the amount of memory.

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  • February 2, 2019 at 9:36 pm
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    Are you driving most of the LED's directly from the chip outputs without resistors?

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  • February 20, 2019 at 12:42 am
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    Thanks loads. You just solved some of my confusion. I've been watching this whole series and decided to get a breadboard kit to play around with. I also finally got around to assembling the Three Fives kit and was trying to use that to make a LED blinker as a first project. Aside from the breadboard kit coming with "100 nF" capacitors that measure out as 47 nF, I hadn't realized yet that this breadboard had split power rails.

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  • March 20, 2019 at 9:33 pm
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    Every time I have been doing some projects with " TTL logic " I have allways used decoupling capacitors, mainly to avoid power starvation.
    It's a Really nice Tutorial You got put together there, I enjoyed it wery much.
    Thank You wery much. Keep up the good work

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  • April 8, 2019 at 9:20 pm
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    I was really hoping that the resetting of the control logic instruction step counter would be done in the EEPROM instead of hard-wiring to T5. This would have enabled real various length operations and allowed a bit of cycle optimization. This could be done with the second EPROM which has an unused IO pin and that could be connected to the instruction microcode step counter reset line. You would program the EEPROM accordingly and this would allow, for example , LDA microcode to reset/finish at T4 and ADD to end/reset at T5. Basically just put a 1 in the EPROM at the end of each instruction microcode to reset the instruction step counter.

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  • April 25, 2019 at 1:10 am
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    I think the whole reset circuit could be made out of the extra gates that are not being used from the logic of the clock and save one chip.
    Anyway, thanks Ben for the great videos!! You're awesome!!

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  • April 28, 2019 at 6:08 pm
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    What does "… these signals will be buffered …" (at 4:23) means?

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  • May 15, 2019 at 9:40 pm
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    if you did not clear the A buffer it could run again and add to that until it goes past 255…thanks very much

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  • May 31, 2019 at 8:49 pm
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    The numbers to be added are given by the last four bits of the programmed program in the ram?

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  • July 11, 2019 at 5:48 pm
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    You have some pretty bad MB-102 board right there. I found that my local electronics shop sells these so I bought one to try it out. Power lines are not broken in the middle, numbers line up with holes and are not upside down on the bottom side. Connections feel decent. Bought 16 of them and building CPU on them. The only problem I ran into was power delivery issue where my chips were getting like 3 volts and not working reliably. Soldering wires to header pins worked really well and now all the chips have steady 5 volts. You just need to look at the MB-102 You are getting. Having correct prints on the board is probably the best bet that the board will be at least half decent.

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  • July 12, 2019 at 11:25 pm
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    Thank you i finally inderstood how pc really works.

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  • July 13, 2019 at 8:06 am
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    I have a question regarding the NAND-Gate circuit. Could you get the inverted reset line before the first NAND gate? To me it looks like you are inverting the same signal twice, which i dont think is needed – but please correct me if im wrong.
    Love your videos!

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  • July 15, 2019 at 10:14 pm
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    soo many blinking lights, soo satisfying @10:50

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  • August 22, 2019 at 11:16 pm
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    why you have your program on volatile memoty? couldnt you just use flash or eeprom to store program?

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  • August 31, 2019 at 3:58 pm
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    Hello! What is your breadboard model? thanks.

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  • September 20, 2019 at 7:21 am
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    Can it run Crysis?

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  • September 23, 2019 at 10:16 am
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    I had some stability issues on my control lines and address bus especially when working on the control logic because for some reason if the control lines ever floated weird shit started happening. My biggest issue was with the 74LS32 in the clock circuit almost burning itself out because of the floating HLT line as I was working on the control logic. I also encountered erratic behaviour from the computer when the clock is running at full speed (the program the counts to 42 is instant at full speed, and I have to use an oscilliscope for debugging). My solution was to all 1k pulldown resisters to the system bus as oppose to the 10k ones and to add a seperate 1k pulldown resister at each module directly where the control signal connects. I found that 10k pulldown resisters didn't pull the voltage low enough to cause the signals to count as low in some places and caused the address bus to float at 1.4v oftern when nothing was connecting it to ground. I also added some big electrolytic caps at varying places along the power rails for higher power draw situations and decoupling caps on the rails also. Now my processor runs at full speed flawlessly completing calculations right at the instant you press the button, right now thats about 450Hz according to my scope, but I might try increase the speed eventually

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  • October 7, 2019 at 5:17 am
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    Hi Ben. How are limiting current to the LEDs? That power usage seems high for that few chips. Maybe I'm missing something tho?

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