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


Siemens used most CPUs from the Series 32000 to build computers, from the first version NS32016 up to the last device coming in quantities, the NS32532. The bus system used by the computers was Multibus. The operating system was based on Unix and called Sinix.

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 a computer system build around the NS32016 and his companion chips. Clock frequency was 10 MHz.

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 Mbytes 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)


The MX300 was a more powerfull computer build around the NS32332 CPU running at 15 MHz. It used the NS32382 MMU but only the NS32081 FPU.

Fig. 4. The MX300 CPU board.

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 task of these chips. Something like this is not found on the PC-MX2 board. 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 MX300 CPU board.

Please notice that even the memory chips are made by Siemens. The memory board shown in figure 6 contains 8 Mbytes DRAM with parity protection. The blue connectors allow expansion for another 8 Mbytes. 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 MX300 memory board.

Both photos of the MX300 boards are available in two times higher resolution. You can download them here.

MX300 CPU Board in high resolution (JPEG)

MX300 Memory Board in high resolution (JPEG)

Second MX300

In July 2016 I got an email from Marcos. He asked me wether I am interested in buying an 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 backside. But this is not true for the CPU boards of Siemens, see Figure 11. All looks perfect ...

Fig. 11. The backside of the CPU board.

I have now nearly two complete MX300 systems. 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.


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 24 August 2016. Next chapter: Tektronix