#mos 6502

Ohio Scientific OSI-300

Apple II (June 1977)

The original Apple II was one of the first highly successful personal computers, released by Apple Computer, Inc. (now Apple Inc.) in 1977. It was designed by Steve Wozniak, while Steve Jobs handled the business strategy. The Apple II played a pivotal role in launching the personal computing revolution.

Key Features:

Release Year: 1977

Processor: MOS Technology 6502 at 1 MHz

RAM: 4 KB, expandable up to 48 KB

Storage: Initially used cassette tapes; later supported 5.25" floppy disks (Disk II)

Graphics: Color graphics support — one of the first home computers to offer it

Display: 24 lines × 40 characters text or low-res color graphics (40×48 pixels, 16 colors)

Keyboard: Built-in QWERTY keyboard (initially no lowercase support)

Expansion: 8 internal slots for add-on cards (e.g., sound, memory, network)

Innovations and Impact:

One of the first PCs sold fully assembled in a case with a keyboard and video output — no need for DIY assembly.

Its color graphics and sound capabilities made it popular for games and multimedia software.

Widely adopted in U.S. schools during the 1980s for educational purposes.

Supported BASIC programming, business software, and early video games.

Legacy: The Apple II series (including the II Plus, IIe, IIc, and IIGS) remained in production into the early 1990s. Its commercial success was crucial for Apple's growth and helped pave the way for the Macintosh.

First Code for 68030

Another blinking light test, but this time rather than free-running the 68030 CPU and using an address line to blink an LED, it's running a small program from ROM. The CPU is clocked at 12.5MHz — the minimum for this 25MHz model — and it is counting down in a loop from 4000 between each blink.

I've wired a register to the uppermost nybble of the data bus, and I'm using the chip enable signal that will be used for the UART to select it. Anything written to the UART's address space will show up on the LEDs.

It took a long time to get to this point because I am using a CPLD for glue logic instead of discrete logic chips. This means I needed to have most of my glue logic programmed and tested in simulation before burning it to the CPLD. But that is one of the strengths of this approach — instead of blind trial-and-error debugging or poring over limited logic analyzer captures, the logic can be simulated. Logic errors are easy to spot when an entire timing diagram is laid out.

I've already wired bus signals to the RAM to begin testing it as well. I'm taking advantage of the 68030's support for various bus sizes and bus termination styles. The RAM and ROM share read/write strobes, but the ROM is on an 8-bit asynchronous bus and the RAM is on a 32-bit synchronous bus. There are a lot of parallel signals (mostly address) shared between RAM and ROM, so it was easy enough to wire them at the same time.

The flash ROM I have is rated for 120ns, which means I had to add in four wait states for proper access timing at 25MHz. What amazed me was two wait states were required for the RAM. I'm using 70ns SRAM, which still would have been fast when this processor was released, and indeed is quite a bit faster than the 100ns DRAM that Apple used in 68030 computers. It makes me wonder if there was ever a zero wait state '030 machine. Thankfully, with a CPLD driving all my logic, wait states are easy to implement with just a handful of registers.

I was looking at your post with the Ohio Scientific OSI-300 6502 trainer board (absolutely gorgeous photography btw), and I had a question. Is there a reason the flat, round, light green cap(?)s are bent flat to the board? It looks like the leads are right overtop of resistors in some places—wouldn't that violate minimum electrical clearance?

I work in electronics manufacturing and I've never seen that style of component bent flat like that, but I'm also far from an expert. I'd love to hear your insight.

Thank you in advance!!

Yeah, I see what you mean about the big green ceramic disc capacitors.

I've seen other examples of OSI-300's, and not all of them have them bent flat like that. Most are standing straight up, and some are just at weird angles. Here's an example I saw at VCF West in 2018:

And here's another one I saw at VCF East in 2015:

However, the example in question doesn't appear to have them flush enough with the circuit board to where the leads are short circuiting against any of the diode/resistor leads.

I also should point out that there's probably a bit of optical trickery at play. I took my photos in the light box with a 105mm macro lens, which compresses the space a bit. This makes the clearances appear less than ideal, but it isn't so bad in person.

It's all moot though, the owner has not powered it up, and asked that I not apply power when I was borrowing it to take photos. I don't think it's at risk of being destroyed by a short circuit any time soon.

Oh hey, that's the Cactus's CPU, RAM, ROM, and serial card.

Wait, the Cactus on the other side of the room. And it's running?!??

How is it running without those cards installed? That can't be right...

The Cactus Integrated SBC Mk III has proven that it can sit in for about half of the cards on the bus, no problem.

Franklin ACE 1000 (1982)

​The Franklin ACE 1000 was an early Apple II Plus clone introduced in 1982 by Franklin Computer Corporation. Designed to offer a more affordable alternative to Apple's offerings, it closely mirrored the Apple II Plus in both hardware and software, including direct copies of Apple's ROMs and operating system. This compatibility allowed the ACE 1000 to run most Apple II software and utilize similar expansion cards.​

Key Features:

Processor: MOS Technology 6502 at 1.0 MHz

Memory: 64 KB RAM

Display: Monochrome output by default; optional color support via an add-on chip

Keyboard: Full upper/lowercase support with auto-repeat functionality

Expansion: 8 internal slots for peripheral cards

Storage: External 143K 5.25" floppy disk drive available

Operating System: Shipped with Franklin DOS, a modified version of Apple DOS 3.3​

Despite its technical merits, the ACE 1000 became the center of a landmark legal case when Apple sued Franklin for copyright infringement. The case, Apple Computer, Inc. v. Franklin Computer Corp., resulted in a ruling that affirmed the copyrightability of software stored in ROM, setting a significant legal precedent in the software industry.​

While the ACE 1000 offered features like a numeric keypad and lowercase text support—enhancements over the original Apple II Plus—it was bulkier and heavier. Today, the Franklin ACE 1000 is considered a collector's item, valued for its role in early personal computing history and the legal battles that shaped software copyright law.

On a side note, the Franklin Ace 1000 made several appearances in popular films. It was seen in the Ghostbusters’ lab in the original 1984 Ghostbusters. You can also see a poster for an ACE 1000 in the background of 1984’s Triumph of the Nerds.

more info: https://computeradsfromthepast.substack.com/p/franklins-ace-1000