Minimal 64x4 Home Computer
github.com
github.com
It is like witchcraft seeing someone produce VGA out with some raw/more tangible chips.
I also think about how like on an Arduino you can have a filesystem, make a makeshift notepad via printing/serial in.
Idk... same with RISC V, if a computer works to me do I care what's under the hood. Anyway I did take a course where you learned about flip-flops/registeres, design your own 8-bit ALU, etc... I can appreciate it again "tangible" vs. a single IC that does everything. It's like those cheap games where they have a single chip under a black blob.
I think what you're missing is: VGA was designed in the era when this was A Thing™. Monochrome/NTSC/CGA/EGA/VGA displays are all about "bit banging," sending signals at the right time. If you can send 1's and 0's faster than the analog reception can update, you can "fake" voltage potentials. I say "fake" because that was actually a way to do it before digital-to-analog converters were easy to implement. Today, we can easily produce chips custom for the purpose; however, "in the beginning" it was really just all about timing.
The witchcraft for me was the fact that while older cards used bit-banging to get signals out the door, it was generally designed with a specific purpose (thus specific timings). If you can get access to the underlying timing control, it [opens a whole new world that will surprise people today](https://www.youtube.com/watch?v=-xJZ9I4iqg8).
I wonder wrt an HDMI to VGA connector how simple it is, direct connections or some chip in the middle.
Yeah for end of days being able to go back to VGA/those analog plugs would be good eg. Red/White/Yellow
A CRT can make do with signals to say "go to the next line now", "go back to the top now". and then just output whatever is coming in on the colour signal. It really means there is no concept of a display mode. It's all just in the timing of the signals on the wires. Plenty of modern hardware with digital internals look at a lot of that and just say "That's not normal so I quit".
Analog devices may make a high pitched whine and then explode, but at least they'll attempt the task they have been given.
People who build modern real-hardware fantasy computers [2] struggle with the cost of the display controller if it is done in an authentic style so they wind up using an FPGA or microcontroller (amazingly easy to do with ESP32 [3])
This thing addresses the problem by reusing many of the parts between the CPU and display controller, plus the contrast is not so stark since the CPU part count is greater than 1, unlike the typical retrocomputer.
It's fascinating! It's a minicomputer in the sense that it is built out of low-integration parts, but it is like a microcomputer in important ways, particularly having the closely integrated display controller.
[1] https://vaibhav-pawale19.medium.com/integrated-circuits-ssi-...
https://www.8bity.cz/files/zx80_schema.pdf
VIDEO comes out of the block of gates roughly center of the schematic.
SYNC comes out of the gates on the center right.
and of course the ZX81 merged the logic chips into one ULA.
There exists a kit to go the other way for a ZX Spectrum to split the ULA logic out into discrete chips again.
Yeah, I really enjoyed Atwood's Maddadam books, although I hungrily consume pretty much everything she writes, so I might be a bit biased.
Seveneves was...okay. Not Stephenson's best, which I consider to be Anathem, but that starts fights so I don't say it out loud all that much. He tends to be hit or miss with me in general, but when he hits, it's a solid land.
Realistically though, we'd be extremely lucky to need the abacus, even.
Maybe I should read everything, but what does this mean?
It also means it is likely too tainted to touch even with a 10m pole.
>Individual licenses apply for hardware and software parts.
part, while I was addressing everything before that.
Around the time of the early microprocessors in the 1970s, vastly greater performance was obtainable via discrete parts, for the simple reason that more parallel stuff could be built than the LSI of the day could accommodate (e.g. 32-bit datapath). He even has a specific X axis point with the MSI 74181 bit slice ALU chip - which was in all the high-performance discrete part CPUs of the day, either that one or the AM2901 which also contained registers.
So X axis should be in net complexity in transistors or gates, regardless of implementation. That being said, the device presented still gets an enormous amount of compute per TTL chip, especially considering no dedicated ALU is involved.
Seen the VGA output on a bunch of retro projects.
I've also seen that there are VGA to HDMI converters available.
But can those do any random non standard res like this one, or are most (or all) of them limited to standard historical resolutions?
VGA has no pixel clock. A line is a set of continuous waveforms for R, G, and B. This means that there is no problem with a mis-matched horizontal resolution, except that the edges may be ugly.
If a VGA->HDMI convert supports 240 lines is a bigger question, and the answer is less certain. Some might not support it. Vintage VGA cards could be convinced to do all sort of weird line rates, much stranger than 240, so a good VGA->HDMI adapter should support it happily.
The OSSC can probably do it. I don't think any of the retrotink boxes support separate sync (which is what VGA provides), which is a shame because those are a great bang-for-the-buck.
Yeah, with XFree86 Modelines :-)
I would guess that a simple VGA to DVI converter simply syncs to the VGA pixel clock, samples the analogue colours, and outputs the digitally encoded values with the same timings.
From a quick look, the oscillator in this machine's schematic runs at 16 MHz. I assume that the pixel clock is derived from this. The DVI specification has a minimum pixel clock of 25 MHz so you couldn't produce a valid DVI stream from this without buffering the pixels and retiming the output in summer way. Well, I suppose since the pixel clock isn't explicit on the VGA cable you could have an imaginary clock which is higher by doubling pixels horizontally.
Ultimately though, success probably varies depending on the converter and the display used. There are quite a lot of standard VESA modes and you can often get away with generating something close-ish to spec.
For more exotic video signals you can use devices like the RGBtoHDMI: https://github.com/hoglet67/RGBtoHDMI
It decodes the input signal into a framebuffer and uses the Raspberry Pi's video core to output the result.
* HDMI is, broadly speaking, a proprietary extension of DVI. You can feed DVI signals though an HDMI connector and it will display anyway.
It is but it's becoming hard to find monitors with dvi connectors, so i asked about hdmi which should be more common.
How you get your ancient analog output to a display with only digital in is becoming a problem. I don't know shit about how good or bad your average solution is so I ask.
[I don't have anything like the toy we're talking about in this thread, but I have a 486 with a Trident 512kb vga card and Syndicate on it in a closet]
Adding an HDMI connector is more likely to get you into expensive licensing discussions than DVI is.