Who remembers bubble memory? For a short while in the early 1980's it was going to be the next big thing in computer
technology, then it was never heard of again. Prime
"Tomorrow's World"
material. (A British TV program that never learned that
predicting is difficult, especially about the future). What was it anyway? What happened to it?
Bubble memory was an astonishing technology, it was a kind of magnetic integrated circuit. A magnetic substrate was made from
artificial garnet. Electrodes and chevron-shaped deposits of magnetic material were deposited over the surface, and the whole
thing was wrapped in two coils at right angles and sandwiched between two permanent magnets. By powering the coils and applying
signals to the electrodes, magnetic 'domains' - effectively tiny isolated magnets - could be created in the magnetic layer. These
were shunted around in serial loops rather like the 'bit buckets' in a CCD, with the chevrons guiding them. Each domain could be in
one of two states, creating the classic binary digit. The electrodes could read and write the bit value as a domain was
shunted past. A 'major-minor' loop design was used to shorten access time, but a drawback of the technology is that, like the
CCD, it does not provide random-access to the data.
The resulting 'module' was bulky and heavy compared to a CMOS device. The image on the top right shows, approximately full-size, a
Texas TIB0203 92 Kbit module
, introduced in 1978. Intel made the 1 Mbit 7110 module and Rockwell International also made devices. In Japan, Hitachi and Fujitsu developed the technology. In the UK, Plessey were involved in bubble memory development.
A number of products incorporating bubble memory did make it to market. The image to the right shows a magnetic bubble memory cartridge
for the
Sharp PC5000 MS-DOS computer.
The Fujitsu FM8 DOS micro also used bubble memory, and Rockwell made bubble memory expansion cards for
their line of micros based on the 6502 CPU. A number of specialised processing devices of various kinds also incorporated bubble
memory. Of course Texas used it, in their Silent700 terminal. However, the one field where bubble memory became important was in computer numerically controlled (CNC) machines, used for milling and and manufacturing complex parts from metal and other materials. Bubble memory became an important storage medium in this field, probably because of its robustness combined with non-volatility. Bubble memory boards for such systems are still available today, maintained and supplied by specialist firms that provide parts for old devices by manufacturers like
Fanuc
and
Strippit .
However, bubble memory never became important commercially. CMOS transistor RAM memory, such as is still used today, proved to be
cheaper to make, and of course simpler. In 1981 production of bubble memory technology ceased. For some great information and
images of bubble memory, have a look
here.
Recently I bought the bubble memory card shown below.
It is a standard ISA-bus card for use in older Intel-based personal computers. It is marked "PCH-3 Bubbl-board" on the front, and "Bubbl-tec® division of PC/M. Inc. COPYRIGHT 1987 MADE IN USA" on the back. The supplier told me that it was a 1Mbit card. It came with a 5.25 inch floppy diskette containing MSDOS driver software, labelled PCH-3. Although I have successfully added the necessary drive to my current PC, it gives an error on trying to read the diskette.
A Web search on Bubbl-tec does result in a few hits, but they are only available in the Google cache without images, and they refer to the QSB-11A which was designed for use in systems from Digital Equipment Corp. (DEC) that used the Q-bus for peripheral interfacing, such as the PDP LSI-11 or the MicroVAX. The description of that board states that it used Intel 7110 bubble memory modules controlled by a Zilog Z80 processor. The PCH-3 seems to have been a completely different board for the PC, using Hitachi technology, but possibly slightly earlier in date than the QSB-11A. Web searches on PCH-3 only return irrelevant hits. Information on this card seems to have been lost.
The card bears three large modules marked Hitachi BDN0153, shown in more detail on the right, which must be the bubble memory devices. I have failed to find any information on these on the Web. It is rather strange that there are three modules, normally chip numbers come in powers of two, unless of course they are something like 6-bit devices arranged three-in-parallel to give a 16-bit output (with two unused). For a bubble memory module, it is relatively low in height and has a large number of pins. Also on the card are four Hitachi LSI chips: one HD63501P, two H4804D and one H4805D-2, as well as a 2764 EPROM and a 6116 SRAM.
If you know anything about Bubbl-tec, or the Hitachi memory device, or have other information about this board, please
I am keen to obtain examples of bubble memory modules by Plessey in the UK, Intel and Rockwell in the US, and any other non-US manufacturers. I know that the Soviet Union made at least one bubble memory module that looks like an Intel clone - does anyone know more about it?
