HP 64000 Emulation System Demonstration

Categories: Microcomputers

Here’s a video I made demonstrating the editor, assembler, linker, and emulator packages for the HP 64000 configured for emulating a Motorola 6809 microprocessor. In the video, the process of assembling and linking source code is shown as well the resulting output. Next, the emulation package is started, and the emulated system executes the code as expected. A manual break is initiated so instruction-by-instruction stepping can be done with the program counter, data, and status register viewable.

The assembly code I wrote was very basic, just a few NOP instructions (no operation) in an infinite loop. The emulator is configured to map “emulation memory” (RAM that exists on the emulation system bus) to the target system bus, which in this case only consists of the emulated 6809 CPU in the emulator pod. Because I had no other external peripherals for this target system, I had the emulator map the entire 64K address space of the emulated 6809 to emulation memory.

Once the emulator is set up, I loaded the emulation memory with the “absolute file” generated by the assembler & linker. This file is just the binary machine code that would normally need written to a ROM IC and connected to the CPU, but having the HP 64K put this data into emulation memory to essentially emulate the ROM is a much quicker process!

Since the creation of this video, I’ve procured an HP 7963B HPIB hard disk drive unit to use as the main boot and storage disk for this system. While using a dedicated computer with a GPIB card running HPdrive worked just fine, I wanted a standalone system that could function without the need for another computer. I’ve found that, while the 64K doesn’t seem to officially support this much newer ESDI hard drive enclosure, it does recognize the disk, format, install OS software, and boot off of it. I used HPdir to backup an image of the drive after the HP 64K installed its OS, then restored that image to another drive find that it still boots. HPdir doesn’t appear to support the 64K’s file system format for viewing and copying files, but that doesn’t matter if I’m just going to create full disk image backups.

By the way, the 7963B unit actually houses three ~300MB ESDI hard drives. Each drive gets their own HPIB address. As I don’t see myself ever filling even one of these drives to max. capacity, I’ve unplugged all but one from the drive unit’s power supply to save them from senseless wear. These two can remain as spares to restore backups to if the first drive fails.