[HN Gopher] Minimal 64x4 Home Computer
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Minimal 64x4 Home Computer
Author : zdw
Score : 134 points
Date : 2025-01-22 16:08 UTC (1 days ago)
(HTM) web link (github.com)
(TXT) w3m dump (github.com)
| nottorp wrote:
| > Monochrome VGA output 400 x 240 pixels
|
| 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?
| jdboyd wrote:
| There are two aspects to consider. They are can a VGA->HDMI
| adapter support 400 pixels wide, and can it support 240 lines.
|
| 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.
| aidenn0 wrote:
| Adapters specifically for 8-bit and 16-bit consoles will
| probably do 240 lines, since 240p was what most of those
| used.
|
| 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.
| indrora wrote:
| The Rt5x can handle various sync pulses (Sync On Green,
| Sync On Luma, SCART sync) and the RT4K can handle "Just
| about anything"
| aidenn0 wrote:
| Can it handle separate hsync and vsync signals though?
| That's what VGA outputs.
| ofrzeta wrote:
| > Vintage VGA cards could be convinced to do all sort of
| weird line rates
|
| Yeah, with XFree86 Modelines :-)
| 2mlWQbCK wrote:
| Or Mode X in some DOS games.
|
| https://en.wikipedia.org/wiki/Mode_X
| komadori wrote:
| A DVI* signal is logically very similar to a VGA one, but with
| a different physical layer. The analogue colour signals are
| replaced with TMDS encoded digital ones, but the pixel clock
| and sync signal work more or less the same way.
|
| 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.
| nottorp wrote:
| > HDMI is, broadly speaking, a proprietary extension of DVI
|
| 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]
| bobdvb wrote:
| You can get a DVI to HDMI adapter which costs less than a
| coffee.
|
| Adding an HDMI connector is more likely to get you into
| expensive licensing discussions than DVI is.
| ge96 wrote:
| When I think about "civilization ending" events this kind of
| compute comes up since it seems more simple/more robust granted
| it can do much less than a modern computer. I also have heard of
| the argument at that time it doesn't matter, you can die from
| sepsis or whatever vs. trying to run a computer.
|
| 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.
| cdumler wrote:
| > It is like witchcraft seeing someone produce VGA out with
| some raw/more tangible chips.
|
| I think what you're missing is: VGA was designed in the era
| when this was A Thing(tm). 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).
| ge96 wrote:
| That demo looked cool, would probably be more impressive if I
| grew up with that kind of tech.
|
| 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
| Lerc wrote:
| You need a chip for VGA->HDMI but they exist, and you can
| buy simple adapters. I think HDMI->VGA adapters might be
| cheaper (I have one in a draw somewhere) , One of the more
| tricky points with HDMI is that they are stricter on what
| they call a valid image and make weird assumptions like All
| your pixels are the same width.
|
| 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.
| PaulHoule wrote:
| Display controllers from the 8-bit era were simple
| conceptually but had a huge parts count, particularly it
| needs to have memory access logic very similar to what is in
| the microprocessor. The earliest home computers (TRS-80 Model
| I, Apple II) had a large parts count which was reduced in the
| next generation (TRS-80 Color Computer, VIC-20) because the
| glue logic and display controllers got the same LSI [1]
| treatment as the CPU.
|
| 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-...
|
| [2] http://www.commanderx16.com/
|
| [3] https://github.com/fdivitto/FabGL
| Lerc wrote:
| Historically, the best example of going it alone without
| display hardware, was the ZX80.
|
| 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.
| PaulHoule wrote:
| See https://archive.org/details/Cheap_Video_Cookbook_Don_
| Lancast...
| bloopernova wrote:
| I've sometimes wondered what it would take to bootstrap up to
| the 555 chip or similar. Is it within the reach of most
| countries with universities?
| cancerhacker wrote:
| Not sure if it's still being sold, but "evil mad scientist"
| had a kit [1] to build a giant 555 from discrete components.
|
| [1]https://www.evilmadscientist.com/2014/555v2/>
| askvictor wrote:
| If you haven't read "A Canticle for Leibowitz" I highly
| recommend it for a perspective of technology after a nuclear
| holocaust.
| ge96 wrote:
| Saved, I just started the 5th Bobiverse book since that
| "recently" came out
| 0xEF wrote:
| I found _Canticle_ dull at first, then the ideas started to
| gel and I was salivating for more post-apocalyptic
| speculation like it. Do you have any other recommendations
| for people who enjoyed it?
| Koshkin wrote:
| > _about "civilization ending" events this kind of compute_
|
| Realistically though, we'd be extremely lucky to need the
| abacus, even.
| anonzzzies wrote:
| > I am in no way associated with any activies selling the Minimal
| 64x4 as a product. Any such activity represents a license
| violation. Individual licenses apply for hardware and software
| parts.
|
| Maybe I should read everything, but what does this mean?
| komadori wrote:
| At least part of it is licensed under a Creative Commons Non-
| Commercial licence.
| snvzz wrote:
| It means it is not Open Source Hardware.
|
| It also means it is likely too tainted to touch even with a 10m
| pole.
| Gormo wrote:
| I think it just means that since he's building this from pre-
| existing off-the-shelf parts, he has no control over any IP
| associated with the components he bought. Which seems fairly
| obvious and uncontroversial.
| MarkusWandel wrote:
| I don't quite get the complexity/performance graph's X axis.
|
| 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.
| K0balt wrote:
| The design should be ported to tiny-tape-out so we can go full
| circle!
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