There is a new Apple-1 Replica

So is there a schematic available for this? Or even a real BOM (as opposed to the extremely vague parts listing on their site that includes such devices as "Display port (IC9)")?

I have to say, especially since it seems to be using at least one ATmega328P, it looks a bit parts-heavy compared to the RC6502 Apple 1 Replica SBC, which does it all with 8 contemporary chips plus an Arduino Nano and I/O expander to emulate the display and keyboard circuitry attached to the PIA.

(I have the RC6502 SBC and I'm pretty pleased with it. It's also pretty easy to expand; I added a second PIA with no difficulty, though it's annoying that none of the address decoding logic on the SBC is brought out, forcing you to duplicate it on expansion boards.)

Ok, I'll put my old fuddy-duddy hat on.  As much as I respect the people that put these projects together, any reproduction or replica of an Apple 1 that doesn't include an Apple Cassette Interface is incomplete.  The sad thing is that an ACI isn't very much additional hardware (or cost).

regards,

Mike Willegal

cjs wrote:

So is there a schematic available for this? Or even a real BOM (as opposed to the extremely vague parts listing on their site that includes such devices as "Display port (IC9)")?

I have to say, especially since it seems to be using at least one ATmega328P, it looks a bit parts-heavy compared to the RC6502 Apple 1 Replica SBC, which does it all with 8 contemporary chips plus an Arduino Nano and I/O expander to emulate the display and keyboard circuitry attached to the PIA.

(I have the RC6502 SBC and I'm pretty pleased with it. It's also pretty easy to expand; I added a second PIA with no difficulty, though it's annoying that none of the address decoding logic on the SBC is brought out, forcing you to duplicate it on expansion boards.)

They're trying to sell a kit. Giving a detailed BOM and schematic would make it easier for people to bypass buying the kit and go directly to the source(s) for parts. Honestly, I would not expect them to give a detailed BOM, either. 

I don't see this as parts-heavy. Since the 6502 does not have a separate I/O port, like the 8080 derived systems, you need some sort of address decoding and memory mapping logic. In addition, you need controllers for the video, keyboard, and storage interface.

Yes,  the RC6502 is simpler, but look at what it's doing. It uses the Arduino to replicate basically all of the I/O hardware. Instead of a keyboard controler and video display controller, the Arduino is doing all of that (presumably by acting as a terminal interface.) Of course, the RC6502 has a bus connector, so it can offload peripheral functions to controller cards, so you could add additional cards to your backplane for video and I/O... which would, of course, bring your part count back up to something similar to the breadboard kit in the OP. 

TomXP411 wrote:

They're trying to sell a kit. Giving a detailed BOM and schematic would make it easier for people to bypass buying the kit and go directly to the source(s) for parts. Honestly, I would not expect them to give a detailed BOM, either.

The selling point of kits is not generally that they contain secret information, but that they're convenient. That's the reason I paid about $70 for my RC6502 Apple I Replica SBC kit, rather than just $15 for the just the bare PCB (sold by the same vendor!) or just downloading the plans and getting the PCB spun myself for $10 or less. For me, even though I have the capability to build the SBC from scratch, it was well worth the extra cost to save sourcing the few parts I don't already have (I was missing only two or three couple of the 11 major parts from my inventory), programming the EEPROM and the AVR MCU, and, should I have chosen that route, spinning the PCB.

In fact, back in the days when kits were a bigger thing, most kit manufacturers (e.g., Heathkit) would offer to sell you the manual for a kit, including complete schematics and BOM, for a small fraction of the kit price ($10-$30, IIRC).

The "secret information" thing makes even less sense when there are a half dozen or more competing products for which full plans and a BOM are available.

Given their target audience, I don't think that SmartyKit is likely to lose any sales at all by making a BOM and even detailed plans available; their target customers don't have the inclination, and likely not the ability, to handle sourcing and programming the parts themselves, particularly since that would increase the debugging load. (This kit is not about debugging a build, but using a working build.)

I don't see this as parts-heavy. Since the 6502 does not have a separate I/O port, like the 8080 derived systems...

You are very confused here. The 8080 family systems have no I/O ports in the sense of a 6820 PIA or similar. They have a separate address space for I/O addresses (confusingly called "ports", but they're just addresses), which is effectively a 17th line on the address bus. These addresses are decoded in exactly the same way as one decodes I/O addresses on a 6502 to enable or disable a peripheral chip. You could make use of this 17th address line to reduce the amount of external address decoding logic you need, but doing so is pretty unusual and not a good idea for good reasons I won't get into here. Regardless, we're comparing two very similar 6502-based systems, not systems with a 6502 versus an 8080.

Before reading the rest of this post, I suggest you have a look at the RC6502 Apple 1 Replica SBC Schematic and make sure you fully understand the address decoding logic. (If you don't, start a new thread saying so and I'll take some time to write up a detailed explanation.)

...you need some sort of address decoding and memory mapping logic.

Right. And, as I said above, it looks to me as if they're doing this with more parts than they need. The RC6502 replica decodes everything—all memory and I/O—with just three chips: a 74138, a 7400 and a 7404. The SmartyKit 1 appears to have five "decoder" chips related to addressing.

In addition, you need controllers for the video, keyboard...

The RC6502 SBC has both, though the "keyboard" and "video" are emulated on a serial interface.

...and storage interface.

What storage interface are you talking about? I don't see any sign of one on the SmartyKit.

Yes,  the RC6502 is simpler, but look at what it's doing. It uses the Arduino to replicate basically all of the I/O hardware.

Actually, the parallel interface to the keyboard and video logic is not emulated; the RC6502 uses an MC6821 PIA for this, just like the original Apple I. (The Apple I normally used an MC6820, but these two chips differ only in details unimportant to this discussion.)

And from what I can see from the breadboard image and other information on the site, the SmartyKit uses two AVR MCUs.

Instead of a keyboard controler and video display controller, the Arduino is doing all of that (presumably by acting as a terminal interface.)

Right. Though to be clear, the 6821 PIA is actually controlling the video and keyboard circuitry being emulated by the Arduino. But in both cases, the actual keyboard and video circuitry are emulated. ...so [on the RC6502] you could add additional cards to your backplane for video and I/O... which would, of course, bring your part count back up to something similar to the breadboard kit in the OP.

Not if done sensibly. If I were to change out the serial interface for a PS/2 keyboard and NTSC video, I'd replace the Arduino and the MCP23S17 port expander with a single Parallax Propeller P8X32A, thus reducing the chip count by one.

For a fresh design, it would also make sense to use the Propeller to handle reset, allowing you to drop the 555, and you end up with a design using 8 ICs, as opposed to the SmartyKit's 15.

I've built the RC6502 Video Terminal (https://github.com/tebl/RC6502-Apple-1-Replica/tree/master/RC6502%20Terminal) but do not have the firmware for the 2 ATMega 328P chips.

Does anyone know where I can get these?

Thank you