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It's quite likely that you've never heard of the following Apple II+ clone. Why? The thing wasn't very successful, as it was announced back in 1984, but wasn't released on the market until 1986.

The special thing about the Spartan was, that it was a kind of add-on module for the Commodore 64, and made it compatible with the Apple II+. Sounds a bit strange? It is, because in the box was almost a complete Apple II+ but in a different housing. Only keyboard and monitor were shared by both devices.

Nevertheless, an interesting idea researched and written up by David L. Farquhar. The hardware can be found from "rarely“ over "very rarely“ to "never" on the relevant platforms. Therefore rather something for collectors than for hobbyists. 

But if you still have this box somewhere in your basement or attic, and don't know what exactly this thing is, then the article will surely make you a little smarter. And Ebay might make you a few colorful bills richer. 💵

Verilog, System Verilog and VHDL all have something in common. In interaction with a FPGA they are all wonderfully suitable to make exciting hardware experiments. From your own 8-bit or RISC CPU over various logic circuits to your own VGA output module - the only limit is your imagination.

And affordable FPGAs are available these days - nothing stands in the way of experimentation.

Unless you are not familiar with at least one of the first three up there. Some are held back by the logical step from circuit design to formal implementation. Others struggle with creating test benches or the complexity of existing tool chains.

In Issue #48 we already spoke about a nice alternative, today we follow up again.

Marek Materzok is the developer of DigitalJS and provides a version that runs in the browser on his website.

Marek limits himself to the Verilog derivatives, there is no VHDL integration yet. But besides Verilog and System Verilog, hex files as well as Lua scripts can be loaded, synthesized, and then provided with a clock signal. A special feature is, that the components cast into code are automatically visualized with the help of ElkJS or Dagre. LogiSim backwards, so to speak.

Really beautiful project that invites to experiment and learn. Especially because a number of modules are included in the form of loadable sample code, and you can also upload and synthesize you own files.

In the last issue we reported on the experiment of Michael Doornbos.

Michael, inspired by Gregorio Naçu's 6502 spec sheet, tried to measure the memory transfer speed of a 6502. As it goes with such things, they end up on HN, and when they end up on HN, you have to expect to be ripped into technical pieces in the comments.

Perhaps inspired by just that (we don't know), Michael gets it going again this week. ♻️

In his latest blog post he revisits the general purpose code from last time and tweaks it on a KIM-1 clone.

Curious? Definitely interesting to read.

Roberto Sancho Villa is one of those guys, who stands next to you at the ice cream shop in a sun hat, glasses and bathroom slippers, lapping up his ice cream, and you'll never know what cool stuff he’s really doing.

Are you familiar with The Computer History Simulation Project? It's not his project, but Roberto has developed interactive GUIs for quite a few of the supported machines that directly emulate the look & feel of the real machines of the 60s, 70s and 80s.

Among others, these are the IBM 360/370, the IBM 701 or the IBM 650. But Roberto is not only dedicated to GUIs. He also rescues (probably) lost software from old PDF and text files found in dusty archives.

One shiny pearl in his github repo is a 3D flight simulator for a 1976 SWTP6800! 😲 

3D. 1976.

Of course we're talking wireframes, but Elite wasn't supposed to be released until 8 years later. (Somehow the demo GIF reminds me of a display animation in Airwolf ... anyone?)

If that's not retro, I don’t know what is.

The cool thing about a nearly-all-things-fpga-retro-machine™ is that you can modify it!

Yep. 🤷‍♂️

And there are indeed people who do just that whenever they get their hands on a piece of hardware that doesn't live up to one or more of its claims. That's what's happened to Dan Sanderson.

Dan is a fast writer, or rather a fast typist. And as happens, when muscle memory is faster than the brain, and fingers are bigger than keyboard-design-standard-experts assume, Dan hits the "CLR HOME" key on his Mega65 too often, while trying to press the non-existent backspace key. 

Outch. 🥴

The solution is close at hand. Why not just modify the modifiable computer? 

In his wonderful article Dan goes into the details of his little adventure, and the result might be interesting for some proud owners of a Mega65. But also for others.

Some people claim that modern ARM and ARM-derived CPUs, such as Apple's current M1 and M2 CPUs, are more or less directly descended from the popular MOS6502, which would thus make the 6502 a RISC design (which of course is not the case).

However, the Advanced RISC Machines definitely won more than one CPU battle, that's for sure. 

And beyond that, ARM - even in modern incarnations - is an interesting architecture, albeit today almost as fragmented and proprietary as other processor architectures.

The history is of ARM is more than just interesting, though, and Talks at Google released an interview with Dave Jaggar - one of the fathers of the architecture and responsible for its success from 1992 to 2000 a few days ago.

At one hour, the talk is quite a beast, but whoever is interested will find everything but boredom here.

Still looking for a summer project? How about a PDP-11? Or better with the Raspberry Pi based remake PiDP-11? For the former, you can find heaps of material on Ebay. For the latter, the Tindie project is currently not available, but at least you can put yourself on the waiting list.

To sweeten the waiting time a bit, you can find a lot of build videos on YouTube. A pretty well done one comes from The Phintage Collector and is from May 22.

At least you can see the end result and judge the quality of the kit. And if you've always wanted a small edition of the not-so-small PDP-11 to call your own, you can handle the wait.