There are Unix Systems running with 8 286 CPUs and 8 287's as far as i rember.

The dual 386 systems were not home PCs. Machines like Compaq System Pro were servers and way out of the league of the average buyer. There was a V-tech dual 486 intended for home use.

SMP didn't become affordable enough for home use until at least the Pentium 2 era and even then it was pretty rare.

DEC Rainbow 100 had 2 CPUs: a Z80 and a 8088. While not really a multiprocessor machine as we understand it today (ie parallel) it was that and it was in 1983 and aimed at desktop users. You could run CP/M on the Z80. Both processors could be used at the same time, but it required a lot of software tinkering. You could give the Z80 a job while your main OS ran on the 8088.

xjas wrote:

Actually I heard some C64 stuff offloaded code to the second 6502 ... in the disk drive. 😁 That counts!

If that counts, then an Amiga counts as well, I suppose.
The copper acted as a second processor. A copperlist is a simple program that you can prepare, so the copper can send commands to the blitter and other parts of the chipset.
So they ran in parallel with the main CPU, and you could synchronize them using interrupts or polling.

I suppose with these examples the C128 should be mentioned.(8502 + Z80/A. I don't know if these can really do work in parallel.)
With arcade machines or game consoles there are several examples with different CPUs. (SEGA Genesis has an 68000 as main CPU and a Z80a for sound. That is certainly not the first such example.)

https://books.google.de/books?id=E9TvMcu1mIwC … l%20486&f=false

-> 486 Dual

hm how can DOS and Win 3.x utilize it ? its listed as preinstalled OS.

matze79 wrote:

hm how can DOS and Win 3.x utilize it ? its listed as preinstalled OS.

DOS and Win3.x have no support for multiprocessing, so it will just act as a single CPU system (much like using these OSes on a current multi-core system).
I suppose it only worked as SMP with Windows NT or other SMP-capable OSes.
They do mention Windows NT specifically.

idspispopd wrote:

With arcade machines or game consoles there are several examples with different CPUs. (SEGA Genesis has an 68000 as main CPU and a Z80a for sound. That is certainly not the first such example.)

Just to make it qualify a little more for the category - I believe on the Genesis/Mega Drive the Z80 could run any kind of code you wanted, even though in practice it was mostly used for sound. It has it's own 8KB RAM within which I presume it can run code without blocking the 68K. I don't know how expensive it is for the 68K to read back from that RAM though.

http://www.cryogenius.com/hardware/z80board/

Z80 as ISA Board, Co Processor 😀

idspispopd wrote:

I suppose with these examples the C128 should be mentioned.(8502 + Z80/A. I don't know if these can really do work in parallel.)

There is a trick to enable both to run simultaneously. However code can run only from the 4 bit color ram then...

Vic20 with a 1541 drive attached. 2*6502 processors running independent.

RoyBatty wrote:

Vic20 with a 1541 drive attached. 2*6502 processors running independent.

Can they both be used to run general purpose code, or is one only usable for operating the floppy drive?

The first MP system that home users made popular was the ABIT BP6 with dual Celerons. Celerons were pretty cheap and Windows 2000 was released soon after making for a nice combination (first NT version you could actually game on).

Most people ran Win9x before 2000 so a MP rig was a waste of money.

There are rare MP 386 and 486 systems around but they seem to run proprietary OS's and were meant for business.

The earliest MP board I have is a Tyan 1562 (Dual Pentium 233's).

shamino wrote:

RoyBatty wrote:

Vic20 with a 1541 drive attached. 2*6502 processors running independent.

Can they both be used to run general purpose code, or is one only usable for operating the floppy drive?

As already mentioned earlier, on C64 there is some software that uploads custom code to the 1541 drive and executes it, reading the results back via the serial bus. It's somewhat limited of course (main problem is getting your data in/out of the drive's memory), but it can be considered 'general purpose'.
This can work just as well on a VIC20.

The earliest known multi proc PC that was home and business that I can think of is the EPSON HX-20. It has two Hitachi 6301 CPU's running at a paltry 614 kHz each. Just over half a megahertz. It was also the first "notebook" type computer as it was released in '82. I know the wiki says '83, but that was world wide. The '82 release was limited and I think it was November or December, but thats still under the wire for '82. I have one and its rather snappy for such a limited little rig. The batteries died on me last year and I have yet to rebuild them. Unfortunately it requires the batteries to run as they are in parallel with its PSU, and I need to build a new battery pack to get it going again. It also has built in storage in the form of a micro cassette, and an expansion port on the left side that allowed custom OS, secondary CPU, or even special hardware like a voice synth. I think it was the first voice synth rig that Hawking used for his now famous computer voice. Oh, and it even had a built in printer that can print graphics. Thats a lot of history and features for a 33 year old notebook.

^^ Just looked that one up. What a neat little machine!
How does it handle the dual-CPUs, is it implemented in software by the application or is there some hardware switching/sharing logic? Can you write multithreaded code in BASIC?

HX-20 owner chiming in here. The second CPU was devoted to controlling I/O functions.

Was the OP referring to symmetric multiprocessor systems? When I think dual CPU, SMP is what comes to mind. Systems like the HX-20, Genesis/Megadrive, C128, etc. are "multi CPU", but only use one primary CPU at a time. The secondary CPUs in these systems either run I/O subsystems or are used for running certain software for backwards compatibility.

Vic20/C64/C128 indeed can use the drives processor to run generic code, provided it fits in the limited 2K of ram. Expansion memory can be added of course and 8k ram expansions were common for copy programs.

Several demos make use of this to calculate things. I am unaware of any commercial software other than copy protections which do.