The Web Site to Remember National Semiconductor's Series 32000 Family


Siemens used most of the CPUs from Series 32000 to build small single-user computers up to large multi-user systems. The hardware was based on the Multibus. The system software was based on Unix and called Sinix. The systems were offered in the second half of the 1980's and beginning of the 1990's. The table below shows the available models in 1989.

Model Type CPU Clock CPUs Memory Ports Drives Drive Types
X20 NS32332 15 MHz 1 4 - 8 MB 4 1 85 MB
MX300 , Model 05 NS32332 15 MHz 1 4 MB 6 1 120 MB
MX300 , Model 10 NS32332 15 MHz 1 4 - 12 MB 12 1 170 / 310 MB
MX300 , Model 20 NS32332 15 MHz 1 8 - 16 MB 18 1 - 2 170 / 310 MB
MX300 , Model 30 NS32532 25 MHz 1 8 - 16 MB 30 1 - 4 170 / 310 MB
MX500 , Model 75 NS32532 25 MHz 2 - 8 16 - 64 MB 48 1 - 6 310 MB
MX500 , Model 85 NS32532 25 MHz 2 - 8 16 - 64 MB 96 1 - 6 337 / 690 MB

The X20 is the only single-user system in the table above. In 1989 the PC-MX2 seems not to be offered any more.

The Sinix systems were very successful in Europe. For example over 1 500 MX500 were sold up to 1989. In the same year the new MX500 models 75 and 85 were introduced. I assume that the predecessor models 70 and 80 were based on the NS32332 CPU.

In 1990 a modified MX300 model 30 was offered and the MX300 model 15 was introduced, see table below. Around 13 000 MX300 systems were sold up to this time. This could be the reason why in 2019 still some systems exist. Unfortunately no MX500 ...

Model Type CPU Clock CPUs Memory Ports Drives Drive Types
MX300 , Model 15 NS32532 25 MHz 1 4 - 12 MB 22 1 170 / 380 / 760 MB
MX300 , Model 30 NS32532 25 MHz 1 8 - 16 MB 44 1 - 2 170 / 380 / 760 MB

The information above was published in two Siemens newsletter: Siemens-Magazin COM, issues 4/89 and 3-4/90.

A former employee of National Semiconducter told me that Siemens ordered a big quantity of NS32532 and NS32381 a few years after the last time buy - they did not expect their NS32532 based workstations to live that long and ran out of components. At that time, the process used to manufacture the chipset was already obsolete, but the fab managed to conjure something.


The PC-MX2 was the smallest computer system of the MX series. Wether it was the first one I don't know. There are rumours that a PC-MX had existed. The PC-MX2 was build around the NS32016 and his companion chips. Clock frequency was 10 MHz. Later a version with the NS32332 CPU was offered. Why the name was PC-MX2 is not clear to me because nothing of the design is similar to an IBM PC.

Fig. 1. The outside of the PC-MX2.

Fig. 2. The inside of the PC-MX2.

Many parts of the computers were build by Siemens, for example the hard disk drive was a Siemens product!

Fig. 3. The CPU board of the PC-MX2.

In figure 3 all the first generation Series 32000 chips are located in the right half. In the left half you can see the memory. The CPU board contains 1 MByte of DRAM which is build of 256-kbit memory chips. The memory is parity protected.

This board has gone! Someone threw it away. Grrrrrrrrr!!!

Some more photos of the lost board are available. You can download them in high resolution.

MX2 CPU Board Detail 1 (JPEG)

MX2 CPU Board Detail 2 (JPEG)

More powerful systems were build around the NS32332 CPU running at 15 MHz. The NS32382 MMU was used but only the old NS32081 FPU.

Fig. 4. A CPU board based on the NS32332. No main memory is placed on these CPU boards.

The photo of the CPU board in Figure 4 shows a lot of support chips. Many PALs, buffers and logic gates are needed. Even three SRAMs from INMOS are used. The type is IMS1423P-35, a 16-kbit device organised 4k * 4. You can see them better in Figure 5 below. They are sitting just in the middle of the board, two of them have the id "D19" and "D20". It would be nice if someone can tell me the job of these chips. Something like this is not found on the boards based on the NS32016 CPU. The 74ALS646/648 devices are 8 bit three state bus buffers with a storage function in each direction. They seem to be the interface to the Multibus. Any narrow package with a paper label on it is a PAL : a "programmable array logic" device. The hardware function of this chip can be defined by the user. The design information is stored in a non-volatile memory inside the PAL.

Fig. 5. The INMOS chips on the NS32332 CPU board.

Please notice that even the memory chips are made by Siemens. The memory board shown in Figure 6 contains 8 MByte DRAM with parity protection. The blue connectors allow expansion for another 8 MByte. At the top edge you see a 96-pin DIN connector. This is a special connection to the CPU board which is used only for memory accesses. The two lower edge Multibus connectors are used only for power delivery.

Fig. 6. The memory board for an NS32332 based CPU board.

Both photos in Figure 4 and 6 are available in two times higher resolution. You can download them here.

NS32332 CPU Board in high resolution (JPEG)

Memory Board in high resolution (JPEG)

Second PC-MX2

In July 2016 I got an email from Marcos. He asked me wether I am interested in buying a MX300. A friend of him has found it on a scrapyard ...

In 2016? 25 years old hardware? I was very surprised. But after a short thinking I said yes. Machines of this kind must be saved! In August I received two boxes from Portugal, see Figure 7.

Fig. 7. The post has arrived. The big box weighed 18.4 kg and the small box 4.8 kg.

Marcos put a lot of effort in packaging to make sure that the goods arrive in good order. At the end Marcos did a great job - thank you very much! I would like to see another offer from him :-)

The big box contained a lot of stuff:

It was not possible to save the power supply and the case due to the weight and the size. The small box contained the important things: the CPU board, a 4 MB memory board, an I/O board and a drive controller board.

Fig. 8. Most of the weight of the big box was the green Siemens documentation.

Fig. 9. The cage containing four boards was sent in the small box.

The CPU board in Figure 10 is identical to the CPU board in Figure 4. It looks like both boards are from the same production run.

Fig. 10. The main thing of the delivery: the CPU board based on the NS32332.

Sometimes boards use tiny wires to fix late design bugs. Most of the time they can be found on the back side. But this is not true for the CPU boards of Siemens, see Figure 11. All looks perfect ...

Fig. 11. The back side of the CPU board.

I have now nearly two complete PC-MX2 based on the NS3232 CPU (Systems based on the NS32016 CPU must have a different software). It would be great if I get one system running. But I don't expect an immediate success. For example I have read about a special Siemens terminal which might be required. And of course the first task will be to read the tapes if possible and save the data on it.

Third PC-MX2

In Spring 2018 I got the opportunity to buy another PC-MX2. The offer was cheap and I could take it away personally. This system uses the NS32016 CPU board.

Fig. 12. The back side of the case showing a lof of 9-pin DB connectors for terminals or printers.

Fig. 13. The CPU board is based on the NS32016. Are the tiny little heatsinks on the processor chips (left) really helpful?

The CPU board in Figure 13 is different from the board in Figure 3. I don't know which one is the newer version. The connector between the CPU board and the memory board in the upper right corner has 50 pins.

Fig. 14. The 3 MByte memory expansion board is based on 108 256-kbit devices from Fujitsu.

MX300 (Ulrich)

In 2017 I learned that there is a running MX300 in Germany. I got in contact with the owner and he send me some photos. Since then I know the difference between PC-MX2 and MX300: it is the size of the system!

MX300 machines have a much bigger case. You can install up to 13 boards to connect a lot of peripheral devices. But it seems that you can only install one CPU board.

Fig. 15/16. The front side of Ulrich's MX300. The label on the back side says that this is a MX300 Model 15.

Fig. 17. This system has a lot of upgrade opportunities.

Fig. 18. The first Siemens NS32532 based CPU board that I have seen.

Fig. 19. The memory board looks very similar to the one for the NS32332 CPU boards. This board has one extension board on top for another 4 MByte.

MX300 (Fritz)

Fritz got by chance a MX300 based on the NS32332 CPU. What surprised him and me most is the fact that this machine is running after some fixing! Not to the point where we can play with the system but up to the login screen. There is hope that Fritz will overcome this hurdle in 2019.

Fritz took a lot of photos from the boards and present them on his website. He also shows a small movie from the boot process. You have to be patient until you see something happening. The machine is not the fastest one...

Fritz did also a readout of the 512-kbit boot EPROM of his NS32332 CPU board. A copy of the binary data is available here. The program starts at address 0.

Fig. 20. The front side of the MX300 without the cover.

Fig. 21. The back side without the cover for the fans.

Fig. 22. Can you imagine the amount of cables for a fully populated system?


In 2017 Richard found a hint that the german museum Pinakothek der Moderne in Munich has a MX500 in his collection. Siemens gave it as a donation for an exhibition of modern industrial design in 1987.

I got in touch with the right person of the museum. Nevertheless it took a long time until the machine went out of store to a place where I could take some photos. The expectations were high but I got a warning...

Fig. 23. What could be a great discovery ...

Fig. 24. ... became a big disappointment!!!

Of course Siemens had not given away a fully functional machine costing hundreds of thousand DM. The exhibition in 1987 was centered around the design of industrial products. What is in was of no interest. And therefore Siemens took everything out. What a shame :-(

Fig. 25. The floppy drive from TEAC and the disk drive had to be in to avoid holes in the front side.

The warning was correct but not very helpful. I had expected not to find everything in place. But to see NOTHING in was really frustrating. Shortly after this experience I decided to fly to Jim Austin's computer museum to see the Encore Multimax!


This is interesting: a price list for Siemens computer products from 1990. I found it at and got the permission to present it here. The currency used is D-Mark which is around half an Euro.

The prices are galactic high! A CPU board with two NS32532 costs around 18.000 ...

Siemens Products Price List (PDF)

This chapter was last modified on 22 January 2019. Next chapter: Tektronix