Read more of this story at Slashdot.
Read more of this story at Slashdot.
The good news is the media will just report it as The God Field.
People learn in different ways, but sometimes the establishment fixates on explaining a concept in one way. If that’s not your way you might be out of luck. If you have trouble internalizing floating point number representations, the Internet is your friend. [Fabian Sanglard] (author of Game Engine Black Book: Wolfenstein 3D) didn’t like the traditional presentation of floating point numbers, so he decided to explain them a different way.
Instead of thinking of an exponent and a mantissa — the traditional terms — [Fabian] calls the exponent as a “window” that determines the range of the number between two powers of two. So the window could be from 1 to 2 or from 1 024 to 2048 or from 32768 to 65536.
Once you’ve determined the window, the mantissa — [Fabian] calls that the offset — divides the window range into 8,388,608 pieces, assuming a 32-bit float. Just like an 8-bit PWM value uses 128 for 50%, the offset (or mantissa) would be 4,194,304 if the value was halfway into the window.
There are a few details glossed over — the bias in the exponent and the assumed digit in the mantissa are in the provided formulas, but the reason for them isn’t as clearly spelled out as it would be for the “classic” explanation. If you want a go at the traditional classroom lecture on the topic, there’s one below.
We’ve talked about floating point representations and their effect on missiles. There was a time when you hated to use floating point because it was so expensive in either dollars or CPU time, but these days even a solder controller can do relatively fast math with floats.
In the early 1980s, there were a plethora of 8-bit microcomputers on the market, and the chances are that if you were interested in such things you belonged to one of the different tribes of enthusiasts for a particular manufacturer’s product. If you are British though there is likely to be one machine that will provide a common frame of reference for owners of all machines of that era: The Acorn BBC Microcomputer which was ubiquitous in the nation’s schools. This 6502-driven machine is remembered today as the progenitor and host of the first ARM processors, but at the time was notable for the huge array of built-in interfaces it contained. Its relatively high price though meant that convincing your parents to buy you one instead of a ZX Spectrum was always going to be an uphill struggle.
So, you never owned a BBC Micro, and this has scarred you for life. Never mind, all is not lost, for now you can have that Acorn experience without scouring eBay for a classic micro, by running one entirely in silicon on a myStorm FPGA board.
To be fair, running classic hardware on an FPGA is nothing new and there have been a few BBC Micros implemented in this way, not to mention an Acorn Atom. But this project builds on the previous FPGA BBC Micros by porting it entirely to Verilog and incorporating some of the bug fixes from their various forks. There are screenshots of the result running several classic games, as well as test screens and a benchmark revealing it to be a faithful reproduction of a 2MHz BBC Micro.
We covered the myStorm board when it arrived last year. We’ve also brought you another FPGA board running as a coprocessor for a real BBC micro.
Thanks [monsonite] for the tip. He also alerts us that the myStorm board’s ARM microcontroller can now be programmed from the Arduino IDE.
My new build. Runs on #RaspberryPi and #Retropie. #RetroGaming #retro #gaming #diy #woodworking #handmade #arcade #OldSchool pic.twitter.com/RfIr4v5nf1
— KJ (@kengjin) September 17, 2017
Impressive build from @kengjin!