Connect a 80287 to a 6502 computer?

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roland
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Connect a 80287 to a 6502 computer?

Post by roland » Sun Jul 05, 2020 11:32 am

I just found an 80287 math coprocessor in a bit box. It must be working as I know it's from my 80286 bitd hosting my Atom-in-PC with floating point in 80287. Now the crazy idea popped up in my mind to connect this to the Atom, modify the Floating Point ROM and use it for FP operations.

Has someone here seen any project that uses a 80287 with a 6502, 6800, 6802, 6809, Z80 or any other 8 bit processor? 6502.org has no information.

Or am I the first one with this crazy idea :lol:
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Re: Connect a 80287 to a 6502 computer?

Post by hoglet » Sun Jul 05, 2020 11:38 am

roland wrote:
Sun Jul 05, 2020 11:32 am
Or am I the first one with this crazy idea :lol:
Yes, I think so :lol:

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Re: Connect a 80287 to a 6502 computer?

Post by fordp » Sun Jul 05, 2020 1:41 pm

I am aware of a maths CoPro attached to a Z180 8 bit processor. I think the project is something like Yet Another Z180 and is on GitHub. If you want fast maths on a Beeb the the PiCopro 32016 with Bas32F if you want BASIC or PiCopro with C or Assembler for super fast everything (compared to a Beeb on its own)
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Re: Connect a 80287 to a 6502 computer?

Post by roland » Sun Jul 05, 2020 3:10 pm

fordp wrote:
Sun Jul 05, 2020 1:41 pm
I am aware of a maths CoPro attached to a Z180 8 bit processor.
I have found this computer. He uses a AMD Am9511A math processor. For now I want to stick to the 80287 because I have this in my bit box. I don't think the Atom will really benefit from such a CPU because not many programs use floating point calculations.
fordp wrote:
Sun Jul 05, 2020 1:41 pm
If you want fast maths on a Beeb the the PiCopro 32016 with Bas32F if you want BASIC or PiCopro with C or Assembler for super fast everything (compared to a Beeb on its own)
We can also develop a special core or just a program on the Pi Zero that acts like a mathematical co-pro. Just like Hoglet and I worked some time on a project to use a PiZero as an extra video adaptor with 640x480 and 256 colours.
hoglet wrote:
Sun Jul 05, 2020 11:38 am
Or am I the first one with this crazy idea
Yes, I think so
Crazy ideas are the key to innovation: what was the person in the world doing when (s)he discovered that you could drink milk from a cow :mrgreen:
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Re: Connect a 80287 to a 6502 computer?

Post by BigEd » Sun Jul 05, 2020 3:34 pm

The 287 does seem to want to talk to a 16 bit bus, so at minimum that's a bit of glue. And it wants to see opcodes and operands fed to it as if from a 286, but that might be something that could be done slowly.

I like the idea of replacing Basic's FP functions with hardware assist though. As you note, a Pi could be set up to do this, either on the Tube port or a 1MHz bus (if a Beeb) or equivalently as a peripheral (on an Atom.) It will sometimes be necessary to import and export five byte floats.

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Re: Connect a 80287 to a 6502 computer?

Post by Kazzie » Sun Jul 05, 2020 5:26 pm

Similarly zany, I found an article about connecting an MM15709 coprocessor to the Acorn System 1, mentioned here. :shock:
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Re: Connect a 80287 to a 6502 computer?

Post by danielj » Sun Jul 05, 2020 5:30 pm

I have one of these in my 480Z:
http://www.cpu-world.com/CPUs/9511/index.html

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Re: Connect a 80287 to a 6502 computer?

Post by dominicbeesley » Sun Jul 05, 2020 6:47 pm

I will follow with interest - I have been looking at something like this but I didn't think of the intel chips!

D

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Re: Connect a 80287 to a 6502 computer?

Post by scruss » Sun Jul 05, 2020 6:51 pm

x87s are really tied to Intel chip internals. It may be a pleasantly futile task to try, though.

Apart from the AM9511/AM9512 previously mentioned, the Motorola 68881 saw some use outside its 68k base. Apparently the Apple IIgs's maths library had support for it. The Micromega (unrelated to the 8-bit company) uM-FPU64 is no longer available: the sole developer died about five years ago.

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Re: Connect a 80287 to a 6502 computer?

Post by roland » Sun Jul 05, 2020 8:28 pm

scruss wrote:
Sun Jul 05, 2020 6:51 pm
x87s are really tied to Intel chip internals. It may be a pleasantly futile task to try, though.
As long as you pretend to be a 80286 the co-pro wouldn't notice :wink:
scruss wrote:
Sun Jul 05, 2020 6:51 pm
the Motorola 68881 saw some use outside its 68k base.
The MC68881 happens to be in my bit box as well. I know what I am going to read during my summer holidays :lol:
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Re: Connect a 80287 to a 6502 computer?

Post by Volhout » Mon Jul 06, 2020 8:31 am

I know that for the PICAXE microcontroller, there is a floating point co processor in a DIP-8 package.

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Re: Connect a 80287 to a 6502 computer?

Post by oss003 » Mon Jul 06, 2020 10:32 am

What about a C8231A, cost about $19,- on Ebay
It does however needs +12V .....

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Re: Connect a 80287 to a 6502 computer?

Post by scruss » Mon Jul 06, 2020 2:36 pm

oss003 wrote:
Mon Jul 06, 2020 10:32 am
What about a C8231A, cost about $19,- on Ebay
The 8231 is a licensed version of the AM9511.
Volhout wrote:
Mon Jul 06, 2020 8:31 am
I know that for the PICAXE microcontroller, there is a floating point co processor in a DIP-8 package.
That was the old Micromega uM-FPU V2. As I said upthread, those went away when the developer died suddenly in 2015.

The OP was looking for stuff in their bits box. If it were me, I'd be reaching for one of the cheap ARM Cortex-M4 boards I have lying around: 100 MHz, 32-bit FPP, a few 5V compatible I/O ports

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