Unbelievably tangential but your dog is very cute and I want to see more pictures!
Wish granted! @the.bessie.report on Instagram
I decided to build a nine-bit computer
21–30 of 71 posts
Re: I decided to build a nine-bit computer
#22Long ago I interned for the group supporting the C-30 ARPANET IMP. At one point the IMP was a 16-bit machine, emulating the old Honeywell (?) minicomputer that the original IMP code was written for. At some point they needed more memory, so they lashed on another 4-bit bit slice, and it became a 20-bit machine.
There was an alternate microcode load for it, which implemented an instruction set similar to that of a PDP-11, and could run an ancient version of Unix. (maybe not so ancient back in 1985, but definitely pre-BSD) We used one or two of those for our development machines, and it was my job to write software tools on them, using C with 20-bit words and 10-bit bytes.
Man, it was a pain in the ass.
Re: I decided to build a nine-bit computer
#23Related question - is there an FGPA simulator / designer which works on OS X?
Re: I decided to build a nine-bit computer
#24Long ago I interned for the group supporting the C-30 ARPANET IMP. At one point the IMP was a 16-bit machine, emulating the old Honeywell (?) minicomputer that the original IMP code was written for. At some point they needed more memory, so they lashed on another 4-bit bit slice, and it became a 20-bit machine. There was an alternate microcode load for it, which implemented an instruction set similar to that of a PDP…
The Unix machine was called C70, right?
Re: I decided to build a nine-bit computer
#25> I decided to build a nine-bit computer
Somehow I was sure that sentence was going to end with "... in MineCraft!"
Re: I decided to build a nine-bit computer
#26See also cLEMENCy 9-bit middle-endian (sic) arch from DEF CON CTF 2017
https://2017.notmalware.ru/89dc90a0ffc5dd90ea68a7aece686544/... (link from https://blog.legitbs.net/2017/07/the-clemency-architecture.h...)
Re: I decided to build a nine-bit computer
#27Regarding the interesting bit (to me) in there about the advantages of FPGAs over an SBC like the Pi (speed)- does anybody know of any blogs or projects where an FPGA's speed helped in a hobby project where software running on an SBC wasn't fast enough? I can imagine a few, mostly real-time projects involving expensive computations (image or pattern recognition maybe?), but I would love to see some concrete examples.
There's a growing community using an Altera Cyclone SBC to create faithful recreations of retro gaming machines. Software emulation by the similar sized Raspberry Pi limits you, and the MiSTer is much more compact than a desktop computer that does have the power for accurate software emulation.
Re: I decided to build a nine-bit computer
#28Regarding the interesting bit (to me) in there about the advantages of FPGAs over an SBC like the Pi (speed)- does anybody know of any blogs or projects where an FPGA's speed helped in a hobby project where software running on an SBC wasn't fast enough? I can imagine a few, mostly real-time projects involving expensive computations (image or pattern recognition maybe?), but I would love to see some concrete examples.
Driving LED matrix displays is a good example, since they require good adherance to timing on the output signal. Especially at high refresh rates. There's lots of hobby projects that get away with just using the CPU, but you're throwing a lot of horsepower at something a cheap CPLD could handle fine. There's also solutions like using the "PRU" in a Beaglebone to drive the display...the PRU is basically a microcontroller that can share memory with the CPU, but can work in a more real-time fashion.
So it's not always raw speed, per se, but anything that's sensitive to timing. Linux on a PI can be busy doing something else and miss a critical time to have output (or read) something. An FPGA based solution is working with known loop/io/etc times that don't change.
Re: I decided to build a nine-bit computer
#29Earlier quoted context omitted.
Basically anything with significant real-time requirements or high bandwidth requires an external FPGA or microcontroller. Embedded Linux is great, but if you’re trying to do something like read from a high-speed ADC then the only way to do it is with an FPGA. The FPGA reads from the ADC at precise intervals and buffers the data. The embedded Linux system can then periodically read the buffer with all of the jitter a…
Noob question, in this instance would a realtime OS or a unikernel also solve the problem?
It's better, but still not the same level of timing guarantees. I suppose, left to right, you would have something like:
SBC/Linux -> SBC/Real-time OS -> General Purpose MCU -> Specialized MCU (Parallax Propeller, for example) -> FPGA/CPLD/DSP
With perhaps some additions to the diagram to account for bit-banging vs actual drivers, speeds where some portion of the left side just isn't fast enough to even kind-of work, slow clock MCUs vs fast clock MCUs, etc.
Re: I decided to build a nine-bit computer
#30Regarding the interesting bit (to me) in there about the advantages of FPGAs over an SBC like the Pi (speed)- does anybody know of any blogs or projects where an FPGA's speed helped in a hobby project where software running on an SBC wasn't fast enough? I can imagine a few, mostly real-time projects involving expensive computations (image or pattern recognition maybe?), but I would love to see some concrete examples.
Driving LED matrix displays is a good example, since they require good adherance to timing on the output signal. Especially at high refresh rates. There's lots of hobby projects that get away with just using the CPU, but you're throwing a lot of horsepower at something a cheap CPLD could handle fine. There's also solutions like using the "PRU" in a Beaglebone to drive the display...the PRU is basically a microcontrol…
That's interesting, looks like the PRU is built into the AM3358 SOC, is that correct?