The 1.8″ IDE Hard Disk Layer allows you to add an iPod hard disk to your RC2014 Zed Mini for booting RomWBW images.
The 1.8″ hard drive itself is most commonly found in classic iPod and can often be picked up cheaply if you don’t have one lying around in your Old Tech Drawer.
The circuit itself is based on the IDE Hard Drive Module. There are a few changes specifically around the use of a 1.8″ HDD. This includes a 40 way flat flex connector instead of the 2.54mm and 2.0mm IDC connectors on the standard module. The 1.8″ HDD need a 3v3 supply so an AMS1117 voltage regulator along with 2 electrolytic capacitors handle this.
This device appears on Port 0x20 which is the default in RomWBW. If you have another device already using this port (eg a IDE Hard Drive Module connected to a 3.5″ drive) then there is a cuttable link under the 74HCT138. Cutting this track and soldering a link between the middle and other pad will put this board on Port 0x60. You will need to make the appropriate change to RomWBW in the config file and create a new ROM image.
Physically this is supplied in a Mini form factor which lines up perfectly with an RC2014 Zed Mini. This module only uses signals from the Standard Bus, but both a Standard Bus and an Enhanced Bus long connector are used so that these pass the signals through for another module or a backplane can be used above this one.
HDD Sourcing
This layer is designed to take a 1.8″ drive which has a 40 pin ZIF socket. As mentioned above, the most common source of these is from iPod Classic 5th, 5.5, 6th or 7th gen or iPod video. If you already have one of these iPods, then upgrading it internally to a modern SD solution will not only give you more space for MP3s, but give much longer battery life (plus it will give you a drive to use here!). Due to so many other people also upgrading their iPods, there are a lot of these drives for sale on eBay and other market places very cheaply.
A lot of companies which specialise in iPod upgrades also have a lot of these drives which they sell cheaply. Places like Elite Obsolete Electronics are a great place to buy tested drives.
Quite a few notebook and netbook computers from the late 90s / early 2000s also had these drives fitted. So, again, check your Old Tech Drawer or take a look on eBay for one.
Drive Imaging
If you are using your own drive, then getting a suitable image on there may be the hardest part. The easiest way is with a 40 pin ZIF toUSB adapter (Such as this one). This will then show up on your computer as a removable drive and you can use tools such as dd, balenaEtcher or Win32DiskImager to copy an .img file on to the drive.
The images themselves can be found in the \Binary directory of RomWBW. There are a lot of “hd1k_…” images in here, and any of these can be used. Note that the hd1k_combo.img is made up of multiple images, and these show up as different slices in RomWBW. You can easily create your own custom image by concatenating the individual images you want. Additional information on how to generate custom disk images is found in the Source\Images ReadMe.txt file.
Assembly
The PCB is supplied with the FFC connector and the AMD1117 regulator already fitted, so there are no SMD parts to worry about. As with other kits, start with the lowest components (diodes, resistors etc) and work up to the taller ones.
To fit the pass-through headers it is easiest to mount the PCB on top of the RC2014 Mini Zed using the supplied hardware, then push the headers through from the top. Whilst holding it all together, turn it on its side and solder enough pins to hold the connector in place. Then remove the HDD PCB and solder the rest of the pins from the bottom.
The short flat flex cable is marked PCB on one end and HDD on the other. It is slightly easier to fit the cable to the PCB first and the HDD second, although it doesn’t make a lot of difference.
The connector on the PCB is opened up by sliding the black retainer forward (ie away from the big chip) a couple of milimeters by pushing from both sides. The FFC should slide in easily with no resistance. Pushing the retainer back towards the big chip will lock the cable in place. Give it a gentle tug just to ensure it is located correctly.
On the HDD side, the black retainer should be angled up (use a fingernail or spudger to do this) and the FFC will slide in easily. Push the retainer back down to clamp the cable in place. A gentle tug should confirm that everything is fitted correctly.
The 1.8″ HDD can be held in place with a double sided sticky pad or two cable ties – or both. This will prevent it from moving around which could place undue stress on the flat flex cable. The 40 pin socket, electrolytic capacitors and resistors on the board provide boundaries to prevent it moving too far anyway.
Usage
RomWBW has native support for this from v3.6.0 onwards. (Earlier releases also have support, however, you will need to downgrade the disk image to one compatible with your release.)
On bootup you should see status messages like this confirming your drive has been detected and the drivers loaded. In this example, PPIDE0 is Disk 4
Typing S at the prompt will show a list of all slices available. In this example, ZSDOS 1.1 is on Slice 1 of Disk 4
Typing the device and slice number for a bootable slice will boot in to that slice. eg 4.1 will boot in to CP/M 3.0
RomWBW will only mount 10 drives by default. You can change which slice a drive points to with the ASSIGN command. For example ASSIGN H:=PPIDE0:15 will mount the Infocom Games drive as H: (Adding Assign commands to your Submit file will run them every time you boot so if you have regular drives as a preference this will save you from typing that each time)
bill of Materials
1 RC2014 1.8 IDE HDD PCB inc FFC Connector & Regulator
1 1.8 Flat Flex Cable
1 CP82C55AZ
1 74HCT04
1 74HCT138
1 3mm Green LED
1 40 pin wide DIL socket
1 14 pin narrow DIL socket
1 16 pin narrow DIL socket
1 6 Pin Long Socket
1 20 Pin Long Socket
1 40 Pin Long Socket
1 1k resistor
4 10k resistor
3 1n4148
3 100nf
1 47uf 25v electrolytic
1 22uf 25v electrolytic
4 m3 nylon nut
4 m3 nylon 6mm
4 m3 nylon m/f standoff