Jun| www.downtowndougbrown.com
Earlier this year, I wrote about how I rescued a special recovery partition from an old Macintosh Performa 550’s dead hard drive. This partition had been lost to time and it was a race to try to save it before the remaining Performa 550 machines out there with their original hard drives were reformatted or destroyed. It has now been preserved on the Macintosh Garden. I have a few updates to that post that I’d like to share.| Downtown Doug Brown
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I was recently poking around inside the original Power Macintosh G3’s ROM and accidentally discovered an easter egg that nobody has documented until now.| Downtown Doug Brown
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I recently found myself needing to change the monitor that a cheap HDMI “dummy plug” pretended to be. It was a random one I had bought on Amazon several years ago that acted as a 4K monitor, and I needed it to be something simpler that didn’t support a 4K resolution. The story behind why is a long one that I’m still figuring out and might eventually become a separate blog post in the future.| Downtown Doug Brown
As part of my research into the Macintosh Performa 550’s factory recovery partition, I paid a lot of attention to eBay listings for these computers. I came to an interesting discovery that I had already suspected: big CRT-based Macs in this form factor are regularly damaged in shipping after being sold on eBay.| Downtown Doug Brown
I’ve been noticing a lot of fun stories lately about bugs in old software that suddenly showed up in newer Windows versions. For example, here’s an excellent writeup by Silent about a bug in Grand Theft Auto: San Andreas that laid dormant until Windows 11 24H2 came out. MattKC also recently posted a cool video about the massive project of decompiling LEGO Island, which also solved the mystery of the “exit glitch” that happened in newer versions of Windows. Nathan Baggs has also been a...| Downtown Doug Brown
In my last post about hard drives that go bad over time, I hinted at having rescued a lost piece of obscure Apple software history from an old 160 MB Conner hard drive that had its head stuck in the parked position. This post is going to be all about it. It’s the tale of a tad bit of an obsession, what felt like a hopeless search, and how persistence eventually paid off. There’s still an unsolved mystery too, so I’m hoping others will see this and help to fill in the blanks!| Downtown Doug Brown
As part of my work toward an upcoming post about a lost piece of very obscure Mac history that has finally been found, I’ve been playing around with old Apple-branded SCSI hard drives made by Quantum and Conner in the 1990s. What I’m about to describe is already common knowledge in the vintage computing world, but I thought it would be fun to share my take on it anyway.| Downtown Doug Brown
This is the story of how Apple made a mistake in the ROM of the Macintosh Classic II that probably should have prevented it from booting, but instead, miraculously, its Motorola MC68030 CPU accidentally prevented a crash and saved the day by executing an undefined instruction.| Downtown Doug Brown
I’ve recently been on a bit of a repair kick and wanted to tell another fun repair story. I promise my blog isn’t becoming dedicated just to fixing electronics. This was an interesting story as far as parts sourcing goes though, so I thought it would be a cool one to share. Plus, you’ll get to learn how focus control works on webcams with autofocus.| Downtown Doug Brown
The last couple of electronics repairs I’ve written about on this blog were both quite involved. Fixing stuff doesn’t always involve crazy rabbit holes though! Here’s a quicker fix that I recently performed.| Downtown Doug Brown
There have been some past rumblings on the internet about a capacitor being installed backwards in Apple’s Macintosh LC III. The LC III was a “pizza box” Mac model produced from early 1993 to early 1994, mainly targeted at the education market. It also manifested as various consumer Performa models: the 450, 460, 466, and 467. Clearly, Apple never initiated a huge recall of the LC III, so I think there is some skepticism in the community about this whole issue. Let’s look at the situa...| Downtown Doug Brown
Here’s a weird problem that I’ve never seen before, along with my eventual hardware fix. After my previous Elgato Game Capture HD60 S HDMI capture card LED repair escapades, I recently ended up trying to find another modern revision of the same device so I could dump its SPI flash chip in order to be 100% certain that the data I put into the flash for the animations was correct for the newer model. I took a chance and bought one for cheap on eBay that was sold as not working at all, but l...| Downtown Doug Brown
This post has a little bit of everything. Hardware diagnostics, some suspiciously similar datasheets from two separate Taiwan chip manufacturers, and firmware reverse engineering. Read on if that sounds like fun!| Downtown Doug Brown
For the next post in my series about upgrading my Chumby 8’s Linux kernel (here are links to parts 1, 2, and 3), I thought I’d look at what was involved in getting the reboot and poweroff commands working properly. I noticed pretty early during the development process that they didn’t work, which was pretty annoying.| Downtown Doug Brown
This is the next post in my series about upgrading my old Chumby 8’s kernel. Here are links to part 1 and part 2 if you missed them. As a quick summary, I got U-Boot working in part 1 and then got the SD card working in part 2. In this part I’ll describe the complicated process of how I got Wi-Fi working.| Downtown Doug Brown
This is the final post in my blog series about getting my Chumby 8 from 2011 working on a modern 6.x Linux kernel, as opposed to the stock 2.6.28 kernel it came with. Here are links to all of the previous articles where I went into detail about the various obstacles I had to overcome: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, and 12. I guess we’ll finish it off with lucky number 13.| Downtown Doug Brown
As you may remember from my last post on the subject, I fixed a couple of cheap Altera USB Blaster clones in June. I found improved open-source firmware and ported it to the previously useless CH552G-based one while fixing a bug in the process, and I soldered a slower 12 MHz oscillator into the Waveshare FT245+CPLD blaster which magically made it start working reliably in Linux.| Downtown Doug Brown
Sometime back in 2018, I tried out a fresh install of Ubuntu MATE 18.04 on one of my computers and noticed a strange problem when I attempted to install Google Chrome. I clicked the little Firefox icon in the top panel:| Downtown Doug Brown
Way back in part 2 of this series, I first got my Chumby 8 booting into a newer Linux kernel. (Here are links to parts 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 if you want to read the rest of the saga). At that point early on in the project, I had to get the UART driver working. I didn’t spend much time talking about the UART in that post, but it actually gave me a small challenge that I recently had to revisit. I thought it would be fun to tell the full story of the UART struggles I ran into.| Downtown Doug Brown
This weekend I tinkered with my ancient Raspberry Pi. It’s the original Model B from 2012 that only has 256 MB of RAM. I bought it in July of 2012 for $35, and then a few months later they started being manufactured with 512 MB instead. I wish I had waited a little longer to buy mine!| Downtown Doug Brown
As my Chumby 8 kernel upgrade project neared the finish line (read parts 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10 first if you want), I noticed something subtly annoying. The built-in SD/CF card reader was allocating its own dummy block device (/dev/sda) even if no cards were inserted.| Downtown Doug Brown
What follows is the story of how I fixed not one, but two, different flawed Altera USB Blaster clone devices that never worked correctly after I bought them.| Downtown Doug Brown
I’m going to start this post off with the obligatory list of links to the previous parts in the series if you’re new here and are interested in seeing the full story: 1, 2, 3, 4, 5, 6, 7, 8, and 9. This is the tale of how I upgraded my Chumby 8 to run a modern Linux kernel.| Downtown Doug Brown
If you’re new to this series, I’ve been documenting the process I went through upgrading my old PXA166-based Chumby 8’s 2.6.28 Linux kernel to a modern 6.x version. Here are links to parts 1, 2, 3, 4, 5, 6, 7, and 8. At this point in the project, all of the main hardware peripherals were working great. I noticed something odd when running top though. The CPU usage was always really high, and it wasn’t obvious why.| Downtown Doug Brown
After getting many of the PXA16x peripherals working in modern Linux kernels during my Chumby 8 kernel upgrade saga (here are links to parts 1, 2, 3, 4, 5, 6, and 7), I really felt like I was starting to reach the finish line. The display was working well enough to play low-resolution videos, I had basic 2D acceleration up and running, the touchscreen was operational, and Wi-Fi worked flawlessly. Audio was the only major component left to tackle. The Chumby 8 has built-in speakers, a headphon...| Downtown Doug Brown
In my last post, I figured out how to use Apple’s leaked Flasher utility from the 1990s to reflash a ROM SIMM inside of my Performa 630. It’s basically the Mac equivalent of a BIOS update, but only for Apple’s developers. The research involved in that post was quite a journey of reverse engineering from both a software and hardware perspective. I had to disassemble the code to figure out which computers were compatible and what the software was expecting to find. I also had to create a ...| Downtown Doug Brown
After I wrote about the possibility of programmable Mac ROM SIMMs in Quadras a couple of months ago, I suspected that there had been a way for developers at Apple in the 68k Mac era to reflash the ROM in their Macs during development, just like BIOS updates on PCs. The reason I believed this is because the ROM SIMM socket in the Quadras brought out pins for 12V (VPP) and write enable (/WE). I had verified that the write enable pin was going into the memory controller chip in several Mac model...| Downtown Doug Brown
After getting the PWM backlight working in my last post (here are links to parts 1, 2, 3, 4, 5, and 6), there was only one piece remaining for having a fully functional display in my Chumby 8: the touchscreen controller. The display output worked perfectly fine but I couldn’t detect presses on it.| Downtown Doug Brown
TL;DR: The pinout of modern programmable Mac ROM SIMMs needs to be changed for correct operation in Quadras. If you’re interested in how I reached that conclusion, or at least want to see some cool pictures, read on below.| Downtown Doug Brown
Several months ago, Will from CayMac Vintage reached out to me looking to resurrect my old Mac ROM SIMM programmer project. As a quick summary of that project, it provides a convenient way to program custom 64-pin ROM SIMM modules for vintage Macs from the late ’80s to early ’90s. There are several reasons you might want to do this, including: replacing an original ROM module that has gone bad, disabling the startup RAM test to decrease boot time in systems with a lot of RAM, bbraun’s a...| Downtown Doug Brown
I recently ran into an interesting warning on newer versions of ARM GCC, including the latest (as of this writing) Arm GNU Toolchain 12.3.Rel1. In particular I’m dealing with arm-none-linux-gnueabihf-g++. Here’s a very simple example program that demonstrates the warning:| Downtown Doug Brown
I recently released a big update for my Mac ROM SIMM Programmer software which is written using Qt for cross-platform compatibility. As part of the update I wanted to release the Mac build as a universal x86_64/arm64 binary so that M1/M2 Mac users would be able to run it natively. It doesn’t currently compile for Qt 6, although I think I can fix that in the future without too much effort. However, Qt 5.15.9 and later do support creating universal binaries out of the box, so I decided to fig...| Downtown Doug Brown
In the previous post in this series (here are links to parts 1, 2, 3, 4, and 5), I really got the Chumby to start looking like a Chumby. The display was alive! But getting the LCD controller working was really only one puzzle piece when it came to the display. The backlight needed more work so that I could control the brightness, and the touchscreen controller is a completely nonstandard design that is specific to the Chumby.| Downtown Doug Brown
A couple of months ago I stumbled upon a post on Hackaday about an inexpensive open-source USB 2.0 sniffer created by Alex Taradov. This is a really cool project! Normally, USB sniffers like this can cost thousands of dollars, especially if you’re paying for fancy protocol decoding and also want high-speed 480 Mbps support. This one costs about $50 in parts to assemble yourself, although it will take hours to solder and you will need some experience with hot air (or reflow oven) soldering s...| Downtown Doug Brown
At this point in my Chumby kernel upgrade project (parts 1, 2, 3, and 4 here), I had made a ton of progress but there wasn’t really much to show for it because I didn’t have the LCD working. Even though I had put a ton of work into the project, the display was still black. I knew it was time to get it working.| Downtown Doug Brown
My cousin recently got ahold of me, saying that he was having trouble with his Brother FAX-2840 fax machine/laser printer. It still worked fine as a fax machine or copy machine, but he couldn’t print to it from his Windows 10 computer. He has a business where he needs to be able to print forms and receipts for customers, so it’s a big deal when he can’t print. This particular printer only has a USB port for PC connectivity. It’s connected directly to his computer. I went through all t...| Downtown Doug Brown
This is a continuation of my previous post about upgrading the old 2.6.28 Linux kernel that came with my Chumby 8. In that post, I got a modern U-Boot working with SD card support, which is what I needed in order to boot Linux.| Downtown Doug Brown
As I mentioned in my last post, I spent a good chunk of my spare time over the past 6 months working on a project I’ve been thinking about for over a decade. I bought a Chumby 8 in 2011. It’s an 8″ touchscreen device powered by the Marvell PXA166 processor. It is essentially a souped-up digital picture frame with extra capabilities like speakers, a microphone, and Wi-Fi. There are a bunch of little Flash-based “apps” you can install for stuff like pictures, music, sports scores, wea...| Downtown Doug Brown