Designing A Macintosh-to-VGA Adapter With An LM1881

October 7, 2023 by Maya Posch 3 Comments

Old-school Macintosh-to-VGA adapter. Just solve for X, set the right DIP switches and you’re golden.

If you’re the happy owner of a vintage Apple system like a 1989 Macintosh IIci you may know the pain of keeping working monitors around. Unless it’s a genuine Apple-approved CRT with the proprietary DA-15-based video connector, you are going to need at least an adapter studded with DIP switches to connect it to other monitors. Yet as [Steve] recently found out, the Macintosh’s rather selective use of video synchronization signals causes quite a headache when you try to hook up a range of VGA-equipped LCD monitors. A possible solution? Extracting the sync signal using a Texas Instruments LM1881 video sync separator chip.

Much of this trouble comes from the way that these old Apple systems output the analog video signal, which goes far beyond the physical differences of the DA-15 versus the standard DE-15 D-subminiature connectors. Whereas the VGA standard defines the RGB signals along with a VSYNC and HSYNC signal, the Apple version can generate HSYNC, VSYC, but also CSYNC (composite sync). Which sync signal is generated depends on what value the system reads on the three sense pins on the DA-15 connector, as a kind of crude monitor ID.

Theoretically this should be easy to adapt to, you might think, but the curveball Apple throws here is that for the monitor ID that outputs both VSYNC and HSYNC you are limited to a fixed resolution of 640 x 870, which is not the desired 640 x 480. The obvious solution is then to target the one monitor configuration with this output resolution, and extract the CSYNC (and sync-on-green) signal which it outputs, so that it can be fudged into a more VGA-like sync signal. Incidentally, it seems that [Steve]’s older Dell 2001FP LCD monitor does support sync-on-green and CSYNC, whereas newer LCD monitors no longer list this as a feature, which is why now more than a passive adapter is needed.

Although still a work-in-progress, so far [Steve] has managed to get an image on a number of these newer LCDs by using the LM1881 to extract CSYNC and obtain a VSYNC signal this way, while using the CSYNC as a sloppy HSYNC alternative. Other ICs also can generate an HSYNC signal from CSYNC, but those cost a bit more than the ~USD$3 LM1881.

Increasing System Memory With The Flick Of A Switch

June 5, 2023 by Bryan Cockfield 17 Comments

There’s an apocryphal quote floating around the internet that “640K ought to be enough memory for anybody” but it does seem unlikely that this was ever actually said by any famous computer moguls of the 1980s. What is true, however, is that in general more computer memory tends to be better than less. In fact, this was the basis for the Macintosh 512k in the 1980s, whose main feature was that it was essentially the same machine as the Macintosh 128k, but with quadruple the memory as its predecessor. If you have yet to upgrade to the 512k, though, it might be best to take a look at this memory upgrade instead.

The Fat Mac Switcher, as it is called by its creator [Kay Koba], can upgrade the memory capability of these retro Apple machines with the simple push of a switch. The switch and controller logic sit on a separate PCB that needs to be installed into the computer’s motherboard in place of some of the existing circuitry. The computer itself needs its 16 memory modules replaced with 41256 DRAM modules for this to work properly though, but once its installed it can switch seamlessly between 512k and 128k modes.

Another interesting quirk of the retro Macintosh scene is that the technically inferior 128k models tend to be valued higher than the more capable 512k versions, despite being nearly identical otherwise. There are also some other interesting discussions on one of the forum posts about this build as well. This module can also be used in reverse; by installing it in a Macintosh 512k the computer can be downgraded to the original Macintosh 128k. For this the memory modules won’t need to be upgraded but a different change to the motherboard is required.

A product like this certainly would have been a welcome addition in the mid 80s when these machines were first introduced, since the 512k was released only months after the 128k machines were, but the retrocomputing enthusiasts should still get some use out of this device and be more able to explore the differences between the two computers. If you never were able to experience one of these “original” Macintosh computers in their heyday, check out this fully-functional one-third scale replica.

FPS Game Engine Built In Ancient Macintosh HyperCard Software

January 27, 2023 by Lewin Day 14 Comments

Wolfenstein 3D and Doom are great examples of early FPS games. Back in that era, as Amiga was slowly losing its gaming supremacy to the PC, Apple wasn’t even on the playing field. However, [Chris Tully] has used the 90s HyperCard platform to create an FPS of his own, and it’s charming in what it achieves.

If you’re not familiar with it, HyperCard was a strange combination of database, programming language, and graphical interface system all rolled into one. It made developing GUI apps for the Macintosh platform simpler, with some limitations. It was certainly never intended for making pseudo-3D video games, but that just makes [Chris’s] achievement all the more impressive.

At this stage, [Chris’s] game doesn’t feature any NPCs, weapons, or items yet. It’s thus more of a First Person Walker than First Person Shooter. It features four small rooms with perpendicular, vertical walls, rendered either greyscale or 8-bit color. Now that he’s got the basic engine running, [Chris] is looking to recreate a bit of a Doom RPG experience, rather than copying Doom itself. He hopes to add everything from monsters to weapons, lava, and working HUD elements. If you want to dive in to the code, you can – HyperCard “stacks”, as they’re known, are made up of readily editable scripts.

[Chris] built the project to celebrate the aesthetic and limitations of the original Mac platform. While it could technically run on original hardware, it would run incredibly slowly. It currently takes several seconds to update the viewport on an emulated Mac Plus with 4MB of RAM. Thankfully, emulation on a modern PC can be sped up a lot to help the framerate.

We love seeing HyperCard pushed far beyond its original limits. We’ve seen it before, too, such as when it was used on a forgotten 90s Apple phone prototype. If you’ve been hacking away on retro software yourself, we’d love to see your projects on the tipsline!

Porting DOOM To A Forgotten Apple OS

June 9, 2022 by Bryan Cockfield 28 Comments

Apple hasn’t always had refined user experiences in their operating systems. In the distant past of the ’90s they were still kind of clunky computers that were far from the polished, high-end consumer machines of the modern era. That wasn’t all that Apple offered back then, though. They had a long-forgotten alternative operating system that was called A/UX designed for government applications, and [Keriad] is here to show us this relic operating system and port DOOM to it.

A/UX was designed in the pre-PowerPC days when Macintosh computers ran on Motorola 68000 chips. Luckily, [Keriad] has a Mac Quadra 800 with just such a chip that is still fully-functional. DOOM was developed with the NeXTSTEP operating system which can run on old Macs thanks to another tool called MacX which allows X11 applications to run on Mac. A version of gcc for A/UX was found as well and with the source code in hand they were eventually able to compile a binary. There were several hiccups along the way (including the lack of sound) but eventually DOOM was running on this forgotten operating system.

The main problem with the build in the end, besides the lack of sound, is that the game only runs at 2 – 3 frames per second. [Keriad] speculates that this is due to all of the compatibility layers needed to compile and run the game at all, but it’s still impressive. As far as we know, [Keriad] is the first person to port DOOM to this OS, although if you’re looking for something more straightforward we would recommend this purpose-built Linux distribution whose sole task is to get you slaying demons as quickly as possible.

90s Apple Computer Finally Runs Unsigned Code

April 28, 2022 by Bryan Cockfield 12 Comments

Back in the 90s, the console wars were in full swing. Nintendo vs Sega was an epic showdown at first, but when Nintendo seemed sure to clench the victory Sony came out of nowhere with the PlayStation. While these were the most popular consoles at the time, there were a few others around that are largely forgotten by history even if they were revolutionary in some ways. An example is the Pippin, a console made by Apple, which until now has been unable to run any software not signed by Apple.

The Pippin was Apple’s only foray into gaming consoles, but it did much more than that and included a primitive social networking system as well as the ability to run Apple’s Macintosh operating system. The idea was to be a full media center of sorts, and the software that it would run would be loaded from the CD-ROM at each boot. [Blitter] has finally cracked this computer, allowing it to run custom software, by creating an authentication file which is placed on the CD to tell the Pippin that it is “approved” by Apple.

The build log goes into incredible detail on the way these machines operated, and if you have a Pippin still sitting around it might be time to grab it out of the box and start customizing it in the way you probably always wanted to. For those interested in other obscure Apple products, take a look at this build which brings modern WiFi to the Apple Newton, their early PDA.

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A Macintosh-inspired desk ornament, next to a sceenshot of a classic Macintosh computer desktop

‘Desk Accessory’ Pays Homage To Macintosh

March 21, 2022 by Chris Wilkinson 9 Comments

The retrocomputing community are experts at keeping vintage Apple iron running, but if you’re looking for a simpler way to pay homage to the original Mac, check out this Raspberry Pi powered ‘desk accessory’ by [John Calhoun], fittingly called ‘SystemSix’.

Housed inside a delightfully Mac-shaped piece of laser-cut acrylic, SystemSix is powered by as Raspberry Pi 3, with the graphics displayed on a sizeable 5.83″ e-ink panel. While it resembles a kind of retro-futuristic take on the ‘classic’ Macintosh, SystemSix is the illusion of a fully interactive computer. While non-interactive, the fake desktop is every bit as charming as a real Macintosh display, albeit scaled down. The desktop updates automatically with new information, and presently includes a calendar, dithered lunar phase graphic, and a local weather report.

Clearly calling it a ‘desk accessory’ is a neat play on words. The original Macintosh implemented simple desk accessory programs, such as the calculator and alarm clock, that could run alongside the main application in memory. This was the only way to run more than one application on the Macintosh, before MultiFinder added rudimentary cooperative multitasking in 1987. As such, SystemSix is a functional, stylish and quite literal ‘desk accessory’.

[John] has the full project write-up over on GitHub, and goes into great detail about maintaining the Macintosh aesthetic. For example, the lunar phase graphic uses ‘Atkinson’ dithering. This technique was pioneered by Apple programmer Bill Atkinson, the author of MacPaint and the QuickDraw toolbox on the original Macintosh (and later, Hypercard).

And in case you were wondering – yes, this is the [John Calhoun], who programmed Glider for Macintosh. Now recently retired from Apple, we’re really excited to see what other Macintosh-inspired creations he comes up with. Maybe he will come back around to his Mac-powered MAME cabinets that we covered all the way back in 2005. Or perhaps a sleeper battlestation, like the iMac G4 lampshade that was upgraded with an M1 processor.

A Macintosh Plus computer next to a modern laptop

Remote Desktop Fun For Your Old Macintosh

March 7, 2022 by Chris Wilkinson 10 Comments

Remotely accessing your computer’s desktop, files and network from anywhere has enabled remote working (i.e. ‘work from home’) for the last several decades. Modern PCs have more than enough computational grunt for Virtual Network Computing (VNC), but where does that leave our retro computing community? [Marcio Teixeira] has it covered with MiniVNC, a brand-new remote desktop server for (very) vintage Macintosh computers.

Now before you say anything, it’s true that ChromiVNC has existed for some time, and is a pretty decent remote desktop server for old Macs. However MiniVNC has several significant advantages, most notably, MiniVNC is fully compatible with MacTCP. Apple’s very first TCP/IP networking stack landed on the Macintosh platform with System 6. As such, MiniVNC can serve up a remote desktop on some of the oldest Mac computers, including the Macintosh Plus.

It’s hard to overstate just how cool that is – the iconic Macintosh Plus was released in 1986, runs at a pedestrian 8MHz and supports a maximum of 4MB memory. While much of MiniVNC was written in C++, portions of the software (including TRLE encoding) had to be handwritten in 68K assembly language to ensure decent performance. The entire focus of MiniVNC was on performance and flexibility, with accuracy coming in second, which seems like the right decision. The odd screen artifact and missed update seems to be reasonable trade-off to get this running somewhat smoothly on a Motorola 68000 processor.

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