The primer is a great guide, but being told "don't do it on breadboards" while working on a project intended to run on breadboard (and at a speed slow enough to not mater), it can be discouraging and harder to pick out the information actually relevant to you.
I guess he's trying to simplify, but it's not just the impedance mismatch between the receiver and the transmitter in the general case, but between transmitter and the transmission line at the origin .. then at the other end the transmission line to the receiver.
A good callout. I was conflating point 1 and point 2 on that page of the primer, as I've been thinking about busses a lot lately. I'm still very much learning about these finer points of ... I'd say AC characteristics but that may not even be entirely the appropriate term. I watched that clip from 2:20-3:00 and was in fact reminded of Ben's video discussing "
Why Build A Computer on a Breadboard" which really was my first introduction to some of this physics. I'll have to find some time when I'm more focused to watch that Jack Ganssle video in full.
My point was simply that, for many of the Eater builders coming, they've already decided they're going to use breadboards, and it's a build well known to work on breadboards. Then they're met with this:
#1: Yes, number one! Avoid plug-in (solderless) breadboards for this kind of work! These are the worst of all worlds for computer performance. They require the connecting wires to be the longest of any method (meaning most inductance), have extra capacitance between neighboring tie points, and there's no chance of getting anything even remotely resembling a ground plane. (And no, a piece of sheet metal underneath, connected to ground, does not qualify. Not at all!) Unfortunately people insist on using solderless breadboards for computer construction, and we frequently find the resulting problems reported on the forum with pleas for help to figure it out, when the builder has the connections right but the solderless breadboards' stray inductance and capacitance are keeping his circuit from working. It causes so much grief, yet the builder has a hard time believing that that's the problem!
I'm obviously newish here, so I don't know the stats, but almost all of the questions that say they're building the Eater kit I have read on this board were not ultimately resolved by switching off of breadboards. I fully expect that advice becomes more important the more complicated the build gets. But with the simple "Garth-1" running at 1MHz with only one IC for all the glue logic, the problems I have noticed are more related to wiring mistakes, or problems with interrupts and reset. My sample size is extremely limited, so I defer to the many years of experience above me! Is pushing the hobbyist with an Eater kit to buy wirewrap materials the best direction to push them? What's the
top priority to make an Eater kit build more reliable? I predict it's the Reset circuit...
I'd be surprised if Ben is getting most of his parts from Jameco, as there are more economical sources, such as Digi-Key and Mouser (plus their chip inventory is much more extensive and up-to-date than Jameco's). In most cases per piece prices drastically tumble with a significant quantity purchase, especially in the case of passives. Given that, and some other things, I suspect Ben's cost per kit is probably closer to 55-60 dollars. Obviously, he's not getting rich selling them, but he's also not operating at the break-even point.
The kits are fulfilled directly by Jameco, even if you order from the Eater website. It comes with Jameco packaging and a Jameco invoice with Jameco part numbers. I'm sure there's an economy of scale to the kits they sell for him, but I doubt he's buying up chips on Mouser and then shipping them to Jameco to package up.
Those who are just starting in digital electronics, especially in the realm of building a computer from scratch, have a lot to learn. Watching some U-Toobe videos isn't going to be enough to deal with the knowledge hurdles that have to be leaped in order to have a successful experience.
--
Garth's primer, in my opinion, is worth more than all the Ben Eater videos combined when it comes to dishing out guidance on how to achieve a successful build. One reason is it's a static medium that can be repeatedly studied until understanding has been achieved (and one's studies don't get repeatedly interrupted by commercials). Another reason is Garth has had a lot of real-world experience with the 6502 that includes practical builds that are used to get work done, not just to blink some LEDs. In the process, he's been able to amass and tabulate all the things that can go south in a build, something which the Eater videos only superficially cover.
And I just want to continue to underline that these intro level materials, where all you are doing is blinking LEDs, is very useful for folks who don't have the knowledge level needed to tackle Garth's primer. That was me, six months ago. There are still pages in the Primer that I read over several times when I need that knowledge (and can rarely pull it up from memory, so indeed, it's great that its there and static). When you're at that level, it's very exciting to have the computer on and blinking LEDs within the first 30m. Blinking 8 LEDs in sequence may
be a successful and complete build for some folks. Yes, there's a whole lot more to go from there, but the enthusiasm and good will generated is something that helps people get into the hobby and learn the basic terms so they can learn the next steps. The folks who come from Ben's videos are "totally new". Garth's primer recommends folks to two out of print books if they're "totally new".
Helping others learn about the fascinating world of the 6502 is what this place is all about, and unlike some other forums, that is the primary focus. When one of us posts a lengthy diatribe on how to get something working, it's a labor of love [...]
Hear hear! I certainly am enjoying sharing my perspective and constantly adding more notes and phrases to my journal to look up!
