After stumbling on Ben Eaters “Hello world from scratch” [1] I went out and bought the cpu some parts and breadboards. The chip is only a few dollars. It is highly recommended if you want to dive down into computers and digital logic on first principles. Also great fun to get a break from all the screens and layers upon layers of software that I have to deal with daily.
Clocking a 6502 simulator to 15GHz
21–30 of 79 posts
Re: Clocking a 6502 simulator to 15GHz
#22It would be interesting to compare this project to simply converting 6502 assembly into LLVM IR, and letting clangs optimization passes work their magic. Obviously self modifying code would be hard to handle, but every other case ought to work, and the auto-vectorization ought to do amazing things to some loop-heavy code.
a 6502 backend for LLVM has been attempted a couple times[1][2], but the fact that the 6502 only has three registers imposes severe limitations w.r.t. LLVM's calling conventions. [1] https://github.com/c64scene-ar/llvm-6502 [2] https://github.com/beholdnec/llvm-m6502
Other way around - the idea is to create an LLVM frontend for 6502 machine code, and then transpile that code to run on a modern CPU architecture.
Re: Clocking a 6502 simulator to 15GHz
#23It would be interesting to compare this project to simply converting 6502 assembly into LLVM IR, and letting clangs optimization passes work their magic. Obviously self modifying code would be hard to handle, but every other case ought to work, and the auto-vectorization ought to do amazing things to some loop-heavy code.
Is this what you're (roughly) referring to?:
https://andrewkelley.me/post/jamulator.html
> There is a constant struggle between correctness and optimized code. Nearly all
> optimizations must be tossed out the window in the interest of correctnessRe: Clocking a 6502 simulator to 15GHz
#24I was told by Leonard Tramiel (who was my manager at Atari for a while) that the world record for a production 6502 was 25Mhz. This was demonstrated one Friday evening, some time after the beer fridge had been opened in one of the labs. I don't know if they applied any kind of external cooling, or what the benchmark was. Probably it was "keep cranking up the clock until pins stop wiggling or smoke comes out." Not ver…
"until pins stop wiggling"?
I think it should be “start wiggling” as that makes more sense.
Re: Clocking a 6502 simulator to 15GHz
#25Earlier quoted context omitted.
The author showed it at the end of the article. It's the "effective speed" reported by some benchmark programs (including calling subroutines, running for loops, iterating on a string, etc). These are simple and trivial programs and can be highly optimized in a simulator on modern x86_64. Real-world programs, like games, is slower, as acknowledged in the article.
A lot of BBC BASIC programs, doing real work (e.g. Mandelbrot drawing etc.), should have a shot at 10GHz. Games are slower because they are hammering hardware registers external to the JIT (sound, graphics, keyboard polling, timing, etc.) My laptop is an ancient 5th gen i5 with 2 keys having fallen off, so games are down in the 2GHz - 3GHz range for me. (Perhaps the missing keys make all the difference.)
I understand that some people look suspiciously at the 15GHz mark, specially considering this was run in a 4.5GHz processor. What I understand is that this benchmarks are comparing how long it would've taken on a stock 1Mhz 6502, and calculate the "clock speed" obtained as a ratio. So if I'm getting my result 10,000 times faster than a standard 6502, it means I'm at 10GHz.
I also understand that this is possible because the emulator is running on a superscalar processor. Not sure if multicore has anything to do here (the post specifically mentions the high performance of the single-core case for the processor used). Still, considering that processors back in the 6502 era had just one execution port, and superscalars this day have a lot (I think 8? I really lost track of what's usual these days), then the figure makes sense all right, and without involving any kind of multithreading.
Kudos to the authors of the emulator for having a super-optimized system that can effectively and efficiently emulate its target!
Re: Clocking a 6502 simulator to 15GHz
#26I was told by Leonard Tramiel (who was my manager at Atari for a while) that the world record for a production 6502 was 25Mhz. This was demonstrated one Friday evening, some time after the beer fridge had been opened in one of the labs. I don't know if they applied any kind of external cooling, or what the benchmark was. Probably it was "keep cranking up the clock until pins stop wiggling or smoke comes out." Not ver…
"until pins stop wiggling"?
Wiggling a pin - ie: toggling it. Basically means "activity on the pins"
https://www.cypress.com/blog/technical/more-pdl-examples-wig...
Re: Clocking a 6502 simulator to 15GHz
#27I was told by Leonard Tramiel (who was my manager at Atari for a while) that the world record for a production 6502 was 25Mhz. This was demonstrated one Friday evening, some time after the beer fridge had been opened in one of the labs. I don't know if they applied any kind of external cooling, or what the benchmark was. Probably it was "keep cranking up the clock until pins stop wiggling or smoke comes out." Not ver…
"until pins stop wiggling"?
The pins don't physically wiggle. "pins wiggling" is a common metaphor for "the voltage level on a pin is changing".
As a signal driver is toggled at increasing frequencies ('cranking up the clock'), the signal amplitude (voltage difference between the 'high' and 'low' period) starts to drop. At a high enough frequency, the signal will be indistinguishable from noise and 'stops wiggling'.
Re: Clocking a 6502 simulator to 15GHz
#28I was told by Leonard Tramiel (who was my manager at Atari for a while) that the world record for a production 6502 was 25Mhz. This was demonstrated one Friday evening, some time after the beer fridge had been opened in one of the labs. I don't know if they applied any kind of external cooling, or what the benchmark was. Probably it was "keep cranking up the clock until pins stop wiggling or smoke comes out." Not ver…
"until pins stop wiggling"?
Euphemism for when you don't see output pins transition state on a measuring instrument, e.g. oscope.
Re: Clocking a 6502 simulator to 15GHz
#29I want to see a 6502-alike clocked to 15GHz with an exotic semiconductor such as GaAs, InP, SiGe, etc.
Re: Clocking a 6502 simulator to 15GHz
#30It would be interesting to compare this project to simply converting 6502 assembly into LLVM IR, and letting clangs optimization passes work their magic. Obviously self modifying code would be hard to handle, but every other case ought to work, and the auto-vectorization ought to do amazing things to some loop-heavy code.
Self modifying code was the norm. I hated the loss of optimizations you could do when going to a system on non-self-modifying code. I ended up just giving up on assembly.