Olivetti P652: An intresting PC from 1973

Articoli in inglese Nov 23, 2017 No Comments

You might know the history of Programma 101, the first personal computer from 1965. Some people think that it was a guide in the night. But it’s not so.

Olivetti made some PC after the “Perottina”, and I think that P652 is the most interesting that makes a bridge between the old and the new PCs.

But there is a problem: A serious lack of information. If you search something about this computer you’ll find nothing.

So I’ve wrote to the Museo Tecnologicamente, a great museum in Italy, in the city of Ivrea. They’ve sent my request to the maker of the P652: Gastone Garziera.

He’s really kind and has sent me a lot of information about this computer. Maybe he can scan the general manual and put it online!

So, let’s start!

Technique

P652 uses magnetic card to store its programs and information.

Can compute floating point numbers and communicate with external devices.

Differently from Programma 101 It has 2 work register (M and A) and 240 register: 100 directly referenced (with K key) and all supports indirection (with I key). Also there was 8 index register (N) and 4 condition register.

The processor was programmed by Olivetti. In the firmware there was some mathematics functions like SIN, COS, ARC, TAN, EXP and LOG. The Olivetti’s math Angelo Barbieri wrote that functions.

Memory was measured in “position”: Both RAM and ROM had 4096 positions, but in RAM was of 4 bit, in ROM of 16 bit. ROM can host 512 instructions. Typically it hosts complex mathematics and statistics functions.

Programming

P652 language is substantially an assembly with some symbolism, heritage from the Programma 101.

Do you know the jumps in Programma 101? No? It’s not so important.

But P652 has a modern system with labels for the jumps GOTO and with a C instructions for the IF. The C make the next instruction effective if the condition is true, if not, jumps it.

GOTO supports also subroutine!

For math there is also the instruction R>P, that convert polar coordinates in rectangular coordinates and vice versa.

But a strong point of the P652 was its input/output with external drive, scientific machines and sensors. This was commanded by FMT command.

Do you have other information about this computer? Please write in the in comments!

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Mike Sciking

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