If you listen to [Bil Herd] and the rest of the Commodore crew, you’ll quickly realize the folks behind Commodore were about 20 years ahead of their time, with their own chip foundries and vertical integration that would make the modern-day Apple jealous. One of the cool chips that came out of the MOS foundry was the 6500/1 – used in the keyboard controller of the Amiga and the 1520 printer/plotter. Basically a microcontroller with a 6502 core, the 6500/1 has seen a lot of talk when it comes to dumping the contents of the ROM, and thus all the code on the Amiga’s keyboard controller and the font for the 1520 plotter – there were ideas on how to get the contents of the ROM, but no one tried building a circuit.
[Jim Brain] looked over the discussions and recently gave it a try. He was completely successful, dumping the ROM of a 6500/1, and allowing for the preservation and analysis of the 1520 plotter, analysis of other devices controlled by a 6500/1, and the possibility of the creation of a drop-in replacement for the unobtanium 6500/1.
The datasheet for the 6500/1 has a few lines describing the test mode, where applying +10 VDC to the /RES line forces the machine to make memory fetches from the external pins. The only problem was, no body knew how to make this work. Ideas were thrown around, but it wasn’t until [Jim Brain] pulled an ATMega32 off the top of his parts bin did anyone create a working circuit.
The code for the AVR puts the 6500/1 into it’s test mode, loads a single memory location from ROM, stores the data in PORTA, where the AVR reads it and prints it out over a serial connection to a computer. Repeat for every location in the 6500/1 ROM, and you have a firmware dump. This is probably the first time this code has been seen in 20 years.
Now the race is on to create a drop-in replacement of what is basically a 6502-based microcontroller. That probably won’t be used for much outside of the classic and retro scene, but at least it would be a fun device to play around with.
VCF East, the fabulous retrocomputing festival held in Wall, NJ this last weekend was a blast. We had a great time, dropped t-shirts and stickers to just about anyone who wanted one, took a lot of pictures, and shot a lot of video. Now that it’s over it’s time for the post-mortem, with one insanely long post.
We saw some very cool stuff that merited its own post, and much more that we simply didn’t have time to video. The previous posts from VCF East:
There’s still tons more, including a tour of the retrocomputer museum that hosted VCF East. The biggest talk was from [Dave Haynie], lord of the Amiga giving part three of a multi-year talk on the soap opera that was Commodore International.
Click that ‘Read more…’ to see all this.
[Maurizio] loves using his Amiga 500. His classic piece of hardware has been serving him well for years, except for the floppy drive, which recently gave out on him. No problem for [Maurizio], he just cracked his case open and added a Raspberry Pi as a real-time floppy emulator. [Maurizio] didn’t want to make any permanent changes to his A500 case, and more importantly he wanted to use the Amiga’s original floppy drive interface. The latter placed some rather stringent timing requirements on his design.
The interface hardware is relatively simple. Most of the circuit is dedicated to level shifting from the 5v Amiga 500 to the 3.3V Raspberry Pi. A 74LS06 Hex inverter converts the signals to the open collector outputs the A500 requires. [Maurizio] powered his Raspberry Pi from the floppy power connector of the Amiga. His model A Raspberry Pi works fine, but a model B would pull a bit more power (700ma) than the Amiga floppy power supply is capable of providing (550ma). The user interface side of the equation is simple: Two buttons, one used to switch disks, and one to “Write to SD”. Live disk images are stored in the Raspberry Pi’s ram, so the user needs to hit the “Write to SD” button to store any changes to disk before swapping floppies.
The software is perhaps the most interesting portion of this build. [Maurizio] is emulating a floppy drive in real-time – this means emulating MFM encoding in real time. Calls have to be made with a timing accuracy of 2 microseconds. The Pi’s stock Linux Operating system was just not going to cut it. [Maurizio] coded his drive emulator “bare metal”, directly accessing the Arm Processor on the Raspberry Pi. This gave him access to the entire processor, and allowed him to meet the hard timing requirements of the floppy interface.
Continue reading “Raspberry Pi Emulates an Amiga 500 Floppy Drive”
If you want to get an old Apple, Commodore 64, Amiga, or any other retrocomputer up on the Internet, this is for you. [Stian] had an Amiga 500 lying around and wanted to put it on a network. The A500 isn’t expandable, so he needed to look at some sort of adapter to put it on a network. The solution came to him in the form of a Raspberry Pi, a null modem cable, and a few bits of software.
To connect his Amiga to his network, [Stian] made a small serial converter board for his Raspi that breaks out the Tx and Rx pins on the Pi to a 9-pin serial port. With the physical connection to the Pi made, the only thing left to do was to get some software for the Amiga, namely AmiTCP and PPP. It’s not exactly a fast network connection, but this build allows [Stian] to connect to WiFi networks with ancient hardware.
One interesting aspect of [Stian]‘s build is the fact it’s completely transferable to other retrocomputers – everything from old S-100 bus computers to classic macs, apples, and pretty much anything else with a serial port that supports PPP. Even with the expense of a Raspberry Pi, it’s much cheaper than absurdly expensive second-hand SCSI to Ethernet controllers and other tomfoolery.
Archiving data from old floppy disks can be a tedious process at best. Poorly labeled disks combined with slow transfer speeds put it high on the list of things we would rather not do, and it turns out that [Dweller] was of the same opinion. With an estimated 5,000 floppies in his collection, he finally decided it was time to clean house.
With no idea of what was stored where, he decided the best way to go about the process was to read all of the disks, archiving everything, saving the sorting process for later. He originally started by building a floppy autoloader out of Lego Mindstorm parts, which looked good on paper, but performed pretty poorly.
He came across an old floppy duplicator on eBay and figured that since the machine was built for handling gobs of disks, that it was the perfect base for his autoloader. He pulled the mechanical bits from the machine, incorporating them into the rig you see above. He swapped out the duplicator’s brains for an Arduino, which allows him to batch copy his disks and save a picture of each label with little effort.
He says that the system works great, making his life a lot easier (and less cluttered!)
Check out the video below to see his floppy autoloader in action.
Continue reading “Floppy autoloader takes the pain out of archiving 5000 Amiga disks”
EL back-lit keyboard
A couple bucks worth of EL wire gives a nice green glow to [Mark Shasha's] T400 Elite. Hopefully [Jeri Ellsworth] has some time to pull those how-to videos together so that we can make our own EL wire to replicate this hack.
This tiny cannon is right out of Night at the Museum. It works just like its much bigger brothers would; fill with powder, insert cannon ball, and light with a fuse. Both the introduction and the follow-up videos document the destruction of various objects using the diminutive weapon. [Thanks Thorsten]
Don’t close that browser
We use Google Chrome quite a bit because it tends to be more responsive when opening massive numbers of tabs while researching featured hacks. But there’s some things we don’t like about it. Lack of built-in PDF support under Ubuntu comes to mind, but a smaller thorn in our side is that closing the last tab will also close the browser window. [Ted Schaefer] got tired of the same thing so he wrote an extension called Last Tab Standing to trap that last browser tab, opening the default window instead of closing the browser.
Amiga demo winner
Transformers balloon sculptures
If you’re having trouble finding that art piece to fill up your dining room you should consider building transformers out of balloons. The sculpture above is a free-standing Optimus Prime but the artist has also turned out Megatron, Grimlock, and others. [Thanks W01F]
[Retromaster's] Ultimate Floppy Emulator is a wicked display of hardware mastery. It is the culmination of several design stages aimed at replacing an Amiga floppy drive with a modern storage solution. You may be thinking that using an SD card in place of a floppy isn’t all that interesting but this hack does much more. The board, controlled by a PIC32, patches into the Amiga keyboard and monitor. This allows you to bring up an overlay menu for controlling the emulator in order to configure which virtual floppy disk is currently ‘in the drive’. He’s even gone so far as to add a piezo speaker to mimic the sounds the original drive head would make while reading a disk.