This 6502 is as old as me and I test it

There is a lot of argument if the missing ROR instruction is a bug or not. Whatever it is, it was clearly intended to be there but was left out at the last minute, likely due to time constraints for the release for the CPU. Just a handful of months later an updated data sheet was released saying the instruction would be added into future versions of the chip. The ROM we wrote is able to identify (in a running system) if you have a CPU that has a non-functional ROR instruction.

--- Info

Possible TTL shift register
TI 1A5008

--- Video Links

ROM to test for the ROR bug on the Apple II:

Pagetable ROR bug article:

A viewer @DaftdogUK discovered what this is! See Page 102:

MOS 6502 by Chuck Peddle:

SWTPC 6800:

Frank's Channel (IZ8DWF)

Tech Time Traveller's Channel:

The TV Typewriter (Shift register storage):

Link to dumped 256 byte ROM

Adrian's Digital Basement Merch store:

Adrian's Digital Basement ][ (Second Channel)

Support the channel on Patreon:

-- Tools

Deoxit D5:

O-Ring Pick Set: (I use these to lift chips off boards)

Elenco Electronics LP-560 Logic Probe:

Hakko FR301 Desoldering Iron:

Rigol DS1054Z Four Channel Oscilloscope:

Head Worn Magnifying Goggles / Dual Lens Flip-In Head Magnifier:

TL866II Plus Chip Tester and EPROM programmer: (The MiniPro)

TS100 Soldering Iron:

EEVBlog 121GW Multimeter:

DSLogic Basic Logic Analyzer:

Magnetic Screw Holder:

Universal ZIP sockets: (clones, used on my ZIF-64 test machine)

RetroTink 2X Upconverter: (to hook up something like a C64 to HDMI)

Plato (Clone) Side Cutters: (order five)

Heat Sinks:

Little squeezy bottles: (available elsewhere too)

--- Links

My GitHub repository:

Commodore Computer Club / Vancouver, WA – Portland, OR – PDX Commodore Users Group

--- Instructional videos

My video on damage-free chip removal:

--- Music

Intro music and other tracks by:
Nathan Divino
@itsnathandivino

[sidehustleshortfilms]

Oh my gosh, I recognized that project box, and in the shots showing the catalog number brought up so many memories of helping my Dad do inventory at the Radio Shack store he mananged in the late 70's, early 80's. I saw the 276 prefix and new exactly where in the store on Florence Blvd, Florence, AL I would go to grab that project board.

[davidanderson]

I have a white 1976 cpu in the basement along with the Jameco receipt for $75 for it and the 6522 pia I bought in high school my sophomore year. I lived in PA not far from MOS fab. I called and an engineer sent me programming manuals and data sheets. Wire wrapped it up and had a tic tac toe program working on it using an old point of sale terminal. Later ran tiny basic on it in college. Fond memories.. I will probably dig it out when I retire in 3 years. But your video made me remember the gogo days of home computers

[kdswh]

I love when Adrian is at a loss for words. I'm so thankful that he takes the time to make these videos. It's more than simple nostalgia. Many of us grew up loving these 8-bit systems too and the memories are reminders of moments of joy and the learning that came from experimenting.

He's not just preserving history but he's sharing that love and joy with the world.

I can't think of a better way to spend your time.

[miltonhowe]

Adrian literally teared up over a novelty microchip - with a fatal flaw no less. I love it!

[costa_marco]

Your reaction was the nicest thing to watch. I really enjoy your channel. Keep up with the good work. Rest assured that it is really greatly appreciated.

[ShukenFlash]

I just watched a video by TubeTime where he delved into this and found that it wasn't a bug but rather was intentionally just completely left off the chip to make it as simple as possible. So more of an oversight of how important that instruction could be. He was able to find one with the die exposed and confirm that the transistors for ROR just plain didn't even exist in the early version.

[stevehauser]

Adrian, just found your channel and haven't looked at your other videos yet but I just had to comment. You have taken me back to 1975 where at that time we were programing industrial controllers with paper tape readers. When the 6502 came out a whole new digital age was launched in basements and garages, it was a magical time. Thank you for sharing this story for this old man.

[gecsus]

I bought my first Apple ][ in 1979 for $2250. It started me on a lifelong career as a programmer and Network Engineer. I have an original Gold Intel Pentium as a collectable.

[KiraSlith]

A first revision MOS 6502 from the first year of production. You're not kidding, binning that would've been a tragedy, that thing belongs in a museum display!

[Neodra]

I work in E-Waste ... I see things like this all the time and have to take them apart to sort the parts, that board would have been thrown right in the low grade box. I try and keep an eye out for special things, but I am sure I don't always recognize that it's special. I am able to save a few things but I can't save it all. I rationalize a lot of it by saying to myself if we didn't recycle it nothing would be rare. :)

[MobiusHorizons]

This is so cool. I appreciate how you were able to convey the importance of the discovery to people less well steeped in 6502 lore. That is a really awesome discovery, and even more awesome that it runs (aside from the bug) correctly. Thanks so much for sharing.

[bobblum]

I recognized the 1702 EPROM right away, I was in that electronics hobbyist era in the early to mid '70s, went to tech school, and it became my career. Working at different jobs, seeing so many esoteric parts that are no longer made and have no equivalent. So glad you were able to save that little bit of history.

[petesapwell]

Truly Adrian when Franks program (iz8dwf Hi Frank) popped up declaring this was in fact a bugged MOS 6502…Man I burst into tears…I’m surprised you contained your exposure. Simply wonderful…

[pedwards]

Adrian, I'm so glad that I stumbled into your channel so many years ago, I think from an LGR recommendation, when I really just started on modern PC gaming channels and slowly migrated to this time period. At first I thought it was a bit too technical, despite being an electrical and computer engineer, I never went so far as to have the practical and working knowledge you have and went into the business side. Now every week I'm eagerly waiting for your next video to drop, whether it's this channel or your 2nd channel. It's so hard to describe how over time, you became my all time favorite YouTuber, but I think the reaction in this video encapsulates it.

We all live vicariously through you. We are in awe about how you self taught your way to being one of the most knowledgeable early computer repair people on the planet, and yet still be humble enough to reach out for help, while always letting your true passion and excitement come through in your videos. There are some days I see when you drop a 45 or 55 minute video, and I get giddy thinking I need to save this for a long relaxing viewing session before I go off to sleep.

I guess what I'm trying to say is just... thank you. Thank you for reigniting my love of this hardware which originally pushed me to get the degrees I did all those years ago, and remember why I did. Everytime I learn something new from you every episode, and it's got me into tinkering again. I feel like I'm rambling, so I'll stop.

Never change, because whatever it is you are doing... it freaking works.

[RetroGamingWithEdgarRivera]

I'm glad that you didn't throw away because imagine the regrets afterwards and like Indiana Jones said "it belongs into Museum". Very impressive since I never seen this very early version of MOS 6502 before since only the later version of the Chip especially for the one of the most if not the most popular CPU of all time for 8 bit Computers. What a great find my friend.

[jamieangus-whiteoak]

I loved this @adrian! I was studying electronics in 1974-1977, and then did a PhD in computer design.
My one quibble with the video is that the 6502 is NOT a simplified 6800.
Yes most of the original design team came from motorola, and yes the 6501 was pin compatible to the 6800.
However it's architecture is very different to the 6800 and it has a fraction of the instructions. For example it has 2 index registers, and far fewer instructions.
Chuck wanted to build a better chip for control, because he found that people just balked at the $300+ price of the 6800!
Chuck Peddle's vision was for a cheaper chip to do simple interface and washing machine, etc. control. In other words using the microprocessor as replacement logic.
I think he would have loved this application of the chip!
And I love your sheer joy and excitement of having it work! It made my day!😊

[edwardjoyner]

awesome for you Adrian. I could feel the nostalgic emotion. Love it

[mikebarushok]

A 6502 made Christmas week in 1975 becomes a gift 47 years later.

[TechTimeTraveller]

Thanks for the mention! Wow. Now that is a very lucky find. I have one very early 6502, but it's soldered into my OSI 300 trainer. I don't know if I could devise a way to test for the ROR bug as I'm reluctant to remove it. Very cool, Adrian! There may not be real buried pirate treasure, but there is still lots of digital treasure buried away in devices like this waiting to be found!

[minombredepila]

So glad for you Adrian. Your happiness is contagious and we all feel like we have touched this magnificent piece of history. Hope you located it in a privileged place on your bench, so we can admire it in future videos.