I see micromegacorp's FPUs have been mentioned a couple of times here, but we haven't had a conversation about them. They look pretty interesting as a number-crunching coprocessor:
- 32bit floating point operations in 10us or so for simple ones, or 100us for log/trig functions
- 64bit version runs faster, can do single or double precision, has more I/O (and is 28pin vs 18pin)
- lots of registers
- can also do string ops, integer ops, matrix ops, FFT
- operate over SPI or I2C
- available in DIP or surface mount
- internal clock source
- 32bit version works at 5V or 3.3V, 64bit version at 3V3 with some 5V tolerant inputs
- offer some general purpose I/O, analogue inputs, and a serial port
- internal flash and RAM or EEPROM
- can run a user program from onchip memory
- can buffer commands if they arrive faster than execution
- about $20

Datasheets:
http://www.micromegacorp.com/downloads/ ... asheet.pdf
http://www.micromegacorp.com/downloads/ ... asheet.pdf

Very nice!! I'll add them to my llinks page, next to the AWC ones I had. Do you see anything about how long their programming should last? I expect they're probably flash, so they should last longer than any of us will, as opposed to EPROM which was usually only guaranteed to hold the program material for ten years. I did not see what kinds of microcontrollers they're starting with.

Comparison chart at http://www.micromegacorp.com/downloads/ ... 0Chart.pdf .
See where to buy them, at http://www.micromegacorp.com/wheretobuy.html .

They at least used to offer the 8-pin uM-FPU V2 as well. It's not clear if they still do. That's a very compact addition to an SBC though!

I had told about these serially interfaced ones before, but now I have some work ahead, to compare all of these and decide on one to put in my new workbench computer. (I'll still use scaled-integer for most things, but if a compact FPU can be added with very little trouble, it's an easy investment.)

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Thanks for the link to the PAK products - to me, on a quick glance, they look almost as good, but not quite as good. They do offer more I/O than the 32bit uM-FPU though.

Both the AWCE and MicroMega co-processors are based in Microchip PICs. MicroMega did use an different brand of microcontroller for a while but it seems to have gone back to PICs. I'm not sure which one they use but I suspect its a PIC24/33EP rather than a PIC32 in the latest FPU64. The flash retention should be around 100 years.

I've often though about writing one myself, its not a lot of code, especially if you use C. The biggest problem is deciding what kind of register/stack architecture you want to use in the calculation engine.

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Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs