Some Thoughts: Power Supply

The interface requires a 5 Volt DC regulated power source. The IDE drive will typically require a 5 V and 12 V power source, or just 5 volts if you're using a notebook drive.

One of the cheaper sources of such power supplies are those found in PCs. By jumpering some wires on the ATX connector, you should be able to hook up such a power supply to the interface and your drive. The only drawback is that those power supplies are fairly big. If you're using the notebook drive option, you may find it nicer to use a 5 Volt linear power supply, wall-plug-style.

Progress: PET up and running

Pulled the old PET (CBM 8032) out of the garage and plugged it in. INSTANT FAILURE, it only showed some 15000-something bytes free. After opening her up and pushing a DRAM chip back into it's socket (I replaced a defective DRAM chip with a socketed one some years ago) and hey-presto, but now the keyboard wasn't working, you really had to hammer some of those keys... So I took out the keyboard, removed all key-caps and posts and springs, and washed them (minus the springs) in the sink (the lettering is still yellowish, it didn't come off despite scrubbing. Is it nicotine, or by design ?). I then removed the circuit board and 'scrubbed' it using alcohol swabs (70% Isopropyl Alcohol), you get a big packet of these at the pharmacy. I also used them to rub down the conductive small black pads that are on the bottom of each key inside the keyboard assembly. Cleaned the dust off the assembly itself, put it all back together and it's working fine. Hooked the PET up to the GPIB Analyzer and ran some Basic commands, everything working fine. Next step is to dig up and clean my old 8050 drive to see what's going on in the GPIB bus.

Progress: GPIB Analyzer

I got my National Instruments GPIB Analyzer up and running. This runs on (don't laugh) Windows 3.11 !!! OK, it IS funny, I admit it. When was the last time YOU installed Win 3.11 on a PC...

Progress: PCBs ordered

I finished the PCB (Printed Circuit Board) design a few days ago and ordered the first batch of (6) PCBs a few days ago. They should be with me in the first week of January.

Interface Overview

First, let me get some Terminology out of the way:

• I will refer to the Commodore PET / CBM computer simply as the PET. That may not be technically correct, but that's what I'll do because it's short and sweet.
  
• The PET's IEEE-488 port will be called GPIB by me. (You don't call your FireWire port the IEEE1394 port, do you ?)
  
• The interface's RS-232 Serial Communication Port will be called the Serial Port.

Now for the Interface Specifications (preliminary):

The interface has 4 connectors:

1. GPIB (Female IEEE-488, like at the back of a CBM 8050 disk drive)
2. IDE (40 Pin male dual row pin header receptable, like on a PC's motherboard)
3. Serial (9-Pin female Sub-D, like found on a PC, except female)
4. Power (PC Power Supply style, uses 5 Volts DC regulated)

Hookup is simple: Connect the IDE drive to the interface using a standard 40-pin ribbon cable, and to it's power supply. Connect the PET to the interface using a standard PET-to-IEEE-Device cable (or daisy-chain cable). Hook up power to the interface, and that's all she wrote. The serial port stays unconnected for the moment.

After configuration and formatting of the drive, you should be able to access the IDE drive using standard Commodore BASIC commands. Esoteric commands (block-read/write/execute) may not be supported. There will defenitely be support for PRG files, and probably SEQ and REL files.

More on the Hardware:
The interface circuit consists of a Texas Instruments microcontroller (CPU), Texas Instrument GPIB driver ICs and an RS-232/TTL level shifter. Together with the 4 connectors mentioned earlier, they are incorporated on a double-sided circuit board approximately 3" by 3" in size.

There are no SMT components used.

Power must be supplied from an external 5V DC power supply (that is not part of the interface).


The Serial Port:
This is a freebee, so to speak. It's simply an RS-232 port (no handshake lines, just RX and TX) that can be used by the PET to talk to a modem or any other RS-232 device that doesn't absolutely require hardware handshake.


Configuration:
Initially, there was going to be a jumper on the board, and configuration was going to be through the Serial port. I threw that out, accidentally, when I routed some traces on the circuit board to make the board smaller, and I forgot to put the configuration jumper back in. I realized this about 3 days after placing the order for the first batch of prototype circuit boards. So, I figured that configuration through the GPIB port is just as simple. All you have to know is the initial device number (which will be 8), then you'll be able to send commands to the interface to assign different device numbers to it (they will be stored in the interfaces flash memory and are restored upon reset).

Introduction

So you have an old Commodore PET / CBM computer and you want to hook up a harddisk drive ?

Looks like you have 3 options. Starting with the easiest, they are:

Buy a Commodore D9090 or D9060. These are external Commodore Harddisk Drives with a couple megabyte capacity. They have an external IEEE-488 connector and were specifically designed for the PET CBMs. I've got one of those babies.
Pros: Easy to hookup, full PET-DOS support.
Cons: Quite hard to find, big and heavy, uses a lot of power, near impossible to repair


Get a cable that hooks your CBM to your PC's printer port and, with some software, emulate a CBM disk drive on your PC (i.e. use your PC's harddisk). This has already been done, I believe.
Pros: Cheap
Cons: Requires PC to be running, limited PET-DOS support


Buy the PET/CBM IDE interface. You'll have to wait for me to finish developing it, of course. In fact, it may never make it to production...
Pros: Small, integrated, adds RS-232 to your PET (maybe)
Cons: Limited PET-DOS support.


Since you're here, you have probably already toyed with the first 2 options. If not, maybe you should. On the other hand, if the PET/CBM IDE interface sounds appealing to you, then you've come to the right place. Watch this blog to stay informed.