PMS 64 kB SRAM storage drive
One device which has been in fashion for some time now is the USB Flash drive. While reading the January 1986 edition of the British magazine The Micro User, I came across something even more remarkable: the way it used to be done.
Imagine a little USB memory stick, tiny and compact, with 4 GB capacity. Now, put that image to one side and imagine something else: 3.5 × 5.5 × 1.25 inches in size (about the size of a 3.5″ floppy drive), and with a total capacity of 64 kilobytes. Now, how is that for retro?
Indeed, a whole 64 kB of portable
memory. OK, make that 59 kB with the ROS (RAM Operating System) installed: a file system that allows the device to act as a disc drive for file storage. I have no idea how an external device can provide its own file system for accessing itself, but there you have it. The magazine article does not entertain this bizarre issue unfortunately.
The device – by Permanent Memory Systems (I wonder what became of them) for the Acorn BBC Micro – connects to the computer by 9″ of ribbon cable to the 1 MHz bus socket on the underside of the computer’s case; it also seems to need a separate power connection to operate (to the BBC Micro’s auxiliary power out socket). As well as being a storage device, it can serve as an expanded printer buffer, back in the days when your operating system’s printer buffer was miniscule (all of a few bytes) and you had those wonderful dot matrix printers that would grind away at documents forever. Use the PMS RAM module to offload all your data the way you would with a print spooler, and get on with other work. There is even some sort of provision for task-swapping (not to be confused with page-swapping) provided by software on the support disc for the device, something not supported by the host OS. By writing the entire of main memory (itself only 32 kB) to the RAM drive, you could run another program, and return to the first later.
It is also interesting to note that Acorn’s 1 MHz bus – to which you could connect such devices as hard drives and scientific instruments – was a daisy-chained bus with seemingly no need for device IDs or terminators and no known limit to how many devices it can carry. I imagine it did have its limitations of course! [Edit: yes, it does officially need terminating]
At the time that the PMS memory module was brought out, I was a mere five years old, so sadly I have no idea whether these things were popular or not; it is simply interesting to see what was effectively a precursor of today’s USB Flash drives. Incidentally the PMS RAM drive does not even use Flash RAM, but battery backed-up static RAM.
How things have changed…