The Fujitsu Micro 8 and its Bubble Memory Drive

Fujitsu Micro 8

At the VCFB 2021 in Berlin I presented a recent purchase of mine, a Fujitsu Micro 8 computer complete with its Bubble Memory drive option.

If you do not want to the read following post, you can simply watch the video.

Ok, so obviously, you want to read about it. Here we go!

Let’s start with the manufacturer. Fujitsu is is a Japanese multinational information and communications technology equipment and services corporation which was established on June 20, 1935. This makes it one of the oldest operating IT companies after IBM and before HP. Fujitsu manufactured in 1954 Japan’s first computer, the FACOM 100 mainframe, and launched in 1961 its second generation computers (transistorized), the FACOM 222 mainframe. Fujitsu was a major chip manufacturer until 2014 when they spun off their chip manufacturing business. Think of it as a Japanese IBM if you do not know the Japanese market.

At the beginning of the 1980s, personal computers become a hot topic, and Fujitsu decides to enter this market (at this stage they (as other Japanese manufacturers) have alread released their first micro computer, the LKIT-8 kit). In contrast to IBM, Fujitsu wants their first real entry to the personal computer market to be at the very front of the state of the art. Also, they aim both at private owners and at small businesses. So, the list of features of this model, the Fujitsu Micro 8, released in May of 1981 is very impressive:

  • 2 x 6809 CPUs (one Fujitsu 68A09 processor at 1.2 Mhz as the main CPU and one Motorola 6809 @ 1 Mhz as the graphics processor)
  • 64 kB RAM (first usage of 64 kbit DRAM chips in a microcomputer)
  • 48 kB VRAM
  • 44 kB ROM
  • 2 x Bubble Memory drive as an option (first such drive in a microcomputer)
  • graphics with maximally 640×200 pixels in 8 colors
  • many interfaces: cassette, digital RGB, Composite, TV, cartridge, expansion, RS232, printer, analog in

Unfortunately, this list of features does not only wow the consumer, it also makes him/her notably poorer as it requires Fujitsu to ask for a price for the basic model of 218 kYen then which is about 290 kYen today which corresponds to $1982 or 1690 EUR today. This price does not include the many available options as we will see below.

Internal Options:

MB22003 Kanji ROM (2965 JIS Level 1 Kanjis), 16×16 pixel 30‘000 Yen
MB22002 Non-Kanji (figures, symbols) ROM 10‘000 Yen
MB22401 Z80 card 11‘700 Yen
MB28011 8088 card (set with CP/M-86)
MB22601 Bubble holder unit 85‘700 Yen
FBM43CP Bubble cassette (32KB) 35‘000 Yen

External Options:

MB27603 Standard floppy disk drive (8 “)
MB27605 / MB27607 Mini Floppy Disk Drive (5.25 “)
MB27606 / MB27608 Thin mini floppy disk drive for expansion (5.25 “)
MB22605 128KB Bubble Holder Unit
MB27301 12 inch high resolution color CRT 188‘000 Yen
MB26001 System Expansion Unit
MB22603 FDD interface Card 17‘000 Yen
MB27601 5 inch FDD 313‘000 Yen

Operating Systems Options:

SM07217-F023 F-BASIC Ver. 2.0 (So-called DISK BASIC, but it works in RAM without using the main ROM)
SM07217-F061 F-BASIC Ver. 2.2 (128KB bubble cassette)
SM07217-M041 OS-9 / 6809 Level 1
SM07217-M021 FLEX
SM07217-M033 UCSD Pascal
SM07217-M011 CP/M-80 (with Z80 card installed)
CP/M-86 (when 8088 card is installed)

One option we might have to explain non-Japanese readers is the “Kanji ROM” option. What is it and why was it so expensive?

You have to understand that written Japanese consists out of three different character sets. Two of them, Hiragana, and Katakana use relatively simple signs and consists of about only 50 characters each. They can be represented easily using a “normal” 8×8 pixel grid, and they do not require much more memory than Latin characters (also, they do not have upper and lower case). The problem is the third character set, the Kanjis. These are basically Chinese characters (in principle, the reality is more complicated). These are both graphically complex and there are many. They are so complex that a normal 8×8 grid cannot be used because you could not see the differences between the characters. There are also so many that they do not fit into a standard amount of ROM. Therefore, the Kanji option switches the character grid to 16×16 pixels (and quarters the amount of characters on screen), and it provides enough ROM space for the additional almost 3000 different(!) characters. To that end it is delivered in 128 kB consisting of 16(!) additional ROMs for which there are also sockets on the PCB.

My Micro 8 came with the Bubble Memory drive option, the internal Z80 card and the Kanji option. It likes to throw its 1.5A fuse when it gets more than 100V, e.g. 110V…

Let us conclude the view on the core model with a note on its two CPUs. It sounds very promising to have a computer model with two of these components. Does this make the machine twice as fast? Well, no. See, as I mentioned, the 2nd CPU was the chip responsible for the graphics, and this model does not have another dedicated graphics chip. Also, it acts as a complete independent system. It has its own boot ROM, its own memory, and runs its own program. It communicates with the main CPU exclusively using a 128 byte memory area. So the main CPU writes into this shared area (while the graphics CPU is stopped), and afterwards the graphics CPU is re-started. This is not a very efficient way to communicate, and in the beginning it was almost impossible to write graphics intensive programs. Fortunately, one of Fujitsu’s BIOS programmers left several hidden commands in the BIOS. These commands permit to transfer large binary programs to a reserved memory space and JMP. Only after discovering this hacking technique, this model had enough graphics performance for fast games…

Now, the one option that makes the Micro 8 quite unique is the Bubble Memory drive (there are only two other (and later) computer models out there that use Bubble Memory as a standard). So what is Bubble Memory and why did you possibly never have heard about that?

Bubble Memory is a type of non-volatile computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles, each storing one bit of data. Non-volatile means it keeps its data even if the power is switched off, like e.g. Flash memory or a magnetic tape. Bubble memory started out as a promising technology in the 1970s, offering memory density of an order similar to hard drives but performance more comparable to core memory while lacking any moving parts. This led many to consider it a contender for a “universal memory” that could be used for all storage needs (i.e. main memory like RAM or mass memory like a hard drive).

Because of this appeal, by the mid-1970s, practically every large electronics company had teams working on bubble memory. Texas Instruments introduced the first commercial product that incorporated bubble memory in 1977. By the late 1970s several products were on the market, and Intel (later MemTech) released their own 1-megabit version, the 7110. Other companies that produced such chips were Sharp, Hitachi, Rockwell, and Fujitsu. This technology was even produced in the USSR.

In the first half of the 1980, companies offered Bubble Memory for computers, either as an option (here we have e.g. our Micro 8 in 1981, the “MPC BUBDISK” card for the Apple II in 1982 (128 kB for $895), or HP’s 9825A card in 1984 (128 kB for $1900)), or as built-in mass memory in portable computers (like the 1982 GRiD Compass or the 1983 Sharp PC-5000). Another use was Konami’s Bubble System arcade video game system, introduced in 1984. It featured interchangeable bubble memory cartridges on a 68000-based board.

Bubble Memory works as advertised, even if it requires a “warm-up” time before it can be used because it can be operated only if it is at least 30 °C warm. This initial warm-up time can be up to the 85 seconds the Konami system needed after a cold start (and this time “cold” is not meant figuratively).

So, why don’t we used Bubble Memory today? There are two main reasons. First, although Bubble Memory is as fast as core memory, it is much slower than (chip) RAM (which came later). Second, chip RAM and hard disks became cheaper than Bubble Memory quite soon. As a consequence, in 1981 major companies working on the technology closed their bubble memory operations.

Bubble Memory was used also after 1981 due to the only technical advantage it had left: it can store data even without power and it is immune to even severe movements because it does not have moving parts. It was the Flash memory of its day (Flash was not on the market before 1987) and was therefore used in mobile applications until the entire technology disappeared entirely by the late 1980s.

How does Bubble Memory work?

As I mentioned before, the bubbles, small magnetized areas exist on a thin film of magnetic material. This material is arranged to form a series of parallel tracks that the bubbles can move along under an external magnetic field. The bubbles are read by moving them to the edge of the material where they can be read by a conventional magnetic pickup, and then rewritten on the far edge to keep the memory cycling through the material. There is a very instructive animation(?) of such bubble moving through some material which can help imaging you this mechanism:

Taken from

What does a Bubble Memory chip consist of?

Taken from a TI report entitled TIB0203 Magnetic-Bubble Memory and Associated Circuits from November 1978

See the above picture. First, you have the die with the magnetic area itself. It is wrapped in two layers of orthogonal coils. This package is sandwiched between two permanent magnets, and the entire package is housed in some tin case. For a real-life “unwrapping” of a Bubble Memory chip I can recommend Wolfgang Robels corresponding web page ( which has a series of very nice photos.

Let’s come back to the Bubble Memory drive in the Micro 8.

Micro 8 Bubble Memory Drive

The optional Bubble Memory drive inside the Micro 8 has two slots and can therefore use up to two Fujtsu cartridges. These cartridges have a capacity of 32 kB each (later on, 128 kB cartridges were available, but I am not sure whether they can be used in this drive or only in the later, external drive). The cost of the option and the cartridges is enormous: the drive costs 85 kYen, the cartridges 35 kYen each. This made the configuration above cost 155 kYen (or $1400 today)…

As I said at the beginning, the Micro 8 was a very expensive model and it did not sell well. As a reaction, Fujitsu splits the Micro 8 only a year later into the FM-7 for the mass market at a much lower price (and without a Bubble Memory option) and the FM-11 which is aimed at businesses. The FM-7 becomes a very popular model in Japan and is of the “Popular 3” personal computers of that era.

From a collector point of view, currently you can buy Micro 8s at a not too high price in Japan, but one with the Bubble Memory option is very rare and is typically very pricey. In every case, they are quite cool machines.

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