Brian Swetland

Writes the codes. Recovering OS Engineer (BeOS, HiptopOS, Android, LK, Fuchsia). Embedded systems hacker. Hobbyist Digital Designer. Player of video games. Etc.

github: https://github.com/swetland/
frotz.net: http://frotz.net/
experimental: https://socialnotwork.net/@swetland
location: Palo Alto, CA

Public Key

npub1pcxszqyeekhg5uy4qrjx4jk65sq223xukk3azt8h4lhg724e7n3qg5rjk8

NIP-05 Address

swetland_at_chaos.social@momostr.pink

Profile Code

nprofile1qqsqurgpqzvumt52wz2sper2etd2gq99gnwttg739nm6lm5092ulfcsrn7qaa

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npub1pcxszqyeekhg5uy4qrjx4jk65sq223xukk3azt8h4lhg724e7n3qg5rjk8

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Last Notes

2024-08-05 20:48:40

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Customized ASICs for CPU/PPU/glue is not too out there for an early-90's console design in my mind. The ability to (if you really got fancy) support a couple different "app" cpus (6502/65816/Z80/etc) would be fun too and I feel like keeping the programming model and ISA "realistic" is plenty. Having everything be DIPs or whatnot or run at 5V is certainly not essential at least to my way of thinking, but obviously opinions vary.

2024-08-05 20:43:56

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Really, if you're going to drop an ECP5 in, I'd ditch the 65C265 entirely -- you can easily fit a pipelined and cached RV32I or a 68000 in there -- a 65C816 should not be a problem. You could probably fit *two* -- run the OS on one and apps/games/etc on the other. Abandon the clunky peripherals on the C265 for nicer ones, do a VERA++ video engine, and build your dream early 90s console/computer. Prototype it out on a ULX3S or similar.

2024-08-05 20:24:09

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I expect it's all workable but you're going to need a new design to accommodate the latencies involved with external memory compared with doing all the compositing out of on-board BRAM/SRAM blocks. Definitely doable (and the ECP5, even a small one, has a lot more resources and is much faster), but likely requiring a significant rebuild of the VERA core design.

2024-08-05 20:18:37

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Outboard memory would be the way to go. Not sure if you'd be able to guarantee the same exact timing/limits as the original VERA design. You'd certainly be able to have a lot more video/tile/sprite RAM to play with thought. It'd be a big change to the VERA design.

2024-08-05 20:12:35

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How much block ram is available? I think the only possibly issue might be that the VERA design uses 128KBytes of on-board memory in the ICE40UP5K for sprite/tile/etc ram, and I forget if the ECP5's are as generous with BRAM.

2024-08-05 02:29:24

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That falls pretty squarely in "I'd worry that even if not malicious, this could introduce who knows what subtle bugs into the boot/install process" for me. I haaaate debugging crap during installation, so ye olde iso dd'd to a usb stick it will remain for me!

2024-08-05 02:16:21

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Being suspicious of things that people are inexplicably aggressive about feels reasonable to me. I've heard of ventoy (or something similar) and it sounds possibly useful (though I'm pretty content with just dd'ing images to devices as needed), but people being weird about it makes me think maybe I'm fine as is.

2024-08-04 23:53:53

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Yeah, it always seemed a bit dodgy to me, but fixing it to have an actual synchronous external bus interface feels like it'd be tricky (for me at least) without building up a full simulation environment, which is a fair bit of work. Someone with more extensive digital design experience and/or less rusty could probably get it sorted more expediently, I suspect.

2024-08-04 23:38:08

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My read on it is that VERA was designed to handle a 1MHz 6502 bus interface by mostly leveraging the fact that it runs at 25MHz internally rather than doing more extensive CDC handling. I suspect as the external bus clock gets faster, things just generally get iffier.

2024-08-02 03:57:37

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I don't see contiguous RAM being necessary -- and it's pretty rare on actual 80s/90s machines, either because of ROM, peripherals, etc getting in the way on 64K address space machines or there naturally being gaps in larger address space machines.

2024-07-24 04:10:06

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Yeah, I picked up an inexpensive (relatively) binocular microscope about a decade or so ago at the suggestion of a coworker and that, a decent soldering iron, and liberal application of flux goes a long way to make hand soldering SMD parts doable for me.
I find 0603s pretty reasonable to work with. 0402s start getting pretty fiddly and I haven't tried smaller than that. 0805s just seem enormous once you're building boards with mostly (or entirely) SMD parts.

2024-07-15 04:44:07

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There's also still just the standard "simplify and refine a test case to reproduce the issue" -- what's the smallest chunk of code that can, in isolation, cause the problem to occur? Which would be useful to have in any case. While doing this, one can often narrow down software-related issues... is some utility function, generated code, interrupt routine, etc, causing extraneous writes under some circumstances, perhaps?

2024-07-15 04:40:28

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It would require further investigation to understand what the exact issue was.
"Does it work at a lower clock rate?" Is just a common thing to try in the event of possible hardware interaction issues.

2024-07-15 04:21:20

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I forget if you're running at 8+MHz. If so, trying a lower system clock (1 or 2MHz) might be interesting to rule out some sort of timing related issue.

2024-07-15 04:19:24

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Nothing comes to mind. I did not observe a behaviour like that when poking at VERA previously.
From my recollection of the VERA internals, I'm unaware of anything that can put character/tile data into the tilemap other than writes through the external bus interface.
I'd look for unexpected writes coming from somewhere. Maybe drop a logic analyzer on the bus interface, look to count write transactions, run some test code, and see if you observe more writes than you expect to.

2024-07-15 04:06:14

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VERA does not have an output enable line, only a chip select, which must be asserted (low) for any activity to occur.
Write takes priority over read, so you should be able to safely tie /RD low, if you like.
https://github.com/swetland/vera-module/blob/rev4/fpga/source/top.v#L218

2024-05-17 06:21:06

Some context for my occasional WebDev rambling:
For little hobby apps, I'd like to write code that doesn't require constant maintenance to keep from bit-rotting away.
Since the web tech stack seems to support endless backward compatibility and modern browsers are very capable and modern machines are sufficiently powerful to offset all the overhead, it seems like this would be a useful target.
*But* I don't want to depend on tons of constant-evolving and breaking-my-code middleware goop.

2024-05-17 03:56:39

Is it just because I'm weird (or old?) that I find callbacks much easier to understand and reason about than all the async/await/Promise stuff? (looking at some modern-ish javascript example code)
The stuff that supposedly "simplifies" things just seems to make control flow much less obvious to me.

2024-05-15 16:21:24

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TIL that right-click context menus in text fields are a thing. I don't use Chrome, so tried in Firefox and there's Undo and some Copy/Paste stuff, etc. I had no idea!

2024-05-14 19:41:07

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Something that consistently enraged me when I worked at Google... being told "you are not the target user" or "we're building for the 90% use case" when I ran into some frustrating limitation of a product.
Sure, you can't always cover every edge case, but at "Google scale" 10% is a *lot* of people you're leaving hanging.

2024-04-30 21:37:35

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What I miss the most is the "good old days" of the Internet (which I first got access to in the mid-90s) that were driven by protocols more than "sites" and "apps."
Which meant much more choice of user interface (mailreaders, newsreaders, IRC clients, etc), and not having to have a separate browser tab (we barely had browsers, much less tabs!) open for every different forum, chat system, etc, that you interacted with people on.

2024-04-28 17:27:38

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TT provides 8 out, 8 in, and 8 bidir IOs plus rst and clk. For TT07, this design is running the Z80 core at 1/4 the project clock (so 12.5Mhz for the max 50MHz clock) and alternating between control, A0-A7, control, and A8-A15 on the out pins, D0-7 on the bidir pins, control inputs on the in pins:
https://github.com/rejunity/z80-open-silicon/blob/68438f00192e7b2388163e198b330567e6133cb7/src/tt_um_rejunity_z80.v#L24
The README implies that after prototyping on TT07 the plan is ChipIgnite runs for QFN44 and DIP40 packages (presumably classic Z80 pin-compatible).

2024-04-22 06:41:39

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I think the answer is we need to hold out for another decade or two until hobby ASIC fab gets to a suitable level of affordability to start re-manufacturing the classics of the 70s (and modern variants on their themes).
I can dream! Maybe that'll end up being a nice hobby for me in my 60s or 70s.

2024-04-22 06:38:12

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The other thing that I see WASM increasingly being used for is: take a huge pile of software needed to do for a task -- say an FPGA/MCU toolchain -- convert it all to a platform neutral format that can run on any modern desktop at a performance level that's Good Enough, but also in a reasonable sandbox environment, without the need to wrangle the build for every potential target OS.
Kinda horrible but sure beats rewriting it all from scratch to be safe and clean and portable.

2024-04-22 06:25:14

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Sure.
However, for good or ill, the modern web and browser have evolved into a platform-ish thing (and trust me, as an OS engineer I have been involved in extensive arguments with browser folks about how a Browser is NOT an Operating System).
And while I despair of the absurdities of the modern "web tech stack", a mechanism for delivering content other than hypertext documents that works much better than Javascript, yet remains platform neutral is, to my mind, a good thing.

2024-04-22 06:16:45

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Also, WebAssembly is like ActiveX or Java Applets (yes, I know, eww!) but better! (really!).
I have my grumbles with Rust and with WASM, but the combined power of these two much-maligned technologies have managed to resurrect a long-thought-vanquished maligned technology of days past (shockwave flash) and the result is I can once again watch classic StrongBad Emails in their full Vector Animated Glory instead of as sad, artifact-y copies on Youtube.
https://homestarrunner.com/sbemails/58-dragon

2024-04-22 05:51:14

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See, this is a perfect example of objection-to-evangelism getting in the way of potentially-useful-technology!
Because it's increasingly used in many places (far beyond just browsers) as a modern intermediate form that can be very efficiently AOT'd/JIT'd/etc.
Some people also have an instant negative reaction to it being a 32bit environment, but that decision allows for some extremely efficient implementation of runtimes on modern 64bit archs.
There's some good stuff there.

2024-04-22 05:44:27

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For your amusement, past-me grumbling about the WASM spec...
https://chaos.social/@swetland/111271568378452789

2024-04-22 05:38:44

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Yup, it's definitely not a novel approach.
I got interested in WebAssembly as a "portable" intermediate target after seeing how Zim had made use of it for their bootstrapping process.
WASM is another one of those "there's a lot of hype" and "there are some questionable design decisions" things (and ye gods I haaaate how the spec is written, don't get me started) that also has a LOT of good ideas (and has increasingly wide adoption, which is handy too, worse-is-better, etc.)

2024-04-22 05:30:50

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That's actually how my stage-0 compiler works. I had started writing everything in a minimal dialect of C thinking I'd, at some point, machine-translate it to the target language. It wasn't horrible for the lexer, parser, etc, but data structure wrangling, code gen, etc got increasingly ugly. So I hit the reset button and bolted a super-minimal transpiler-to-C on the lexer+parser. Then I can use that to compile the stage-1 compiler written in (a subset of) itself.

2024-04-22 05:05:53

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Probably not something I'd implement, but the goal is compile-to-native with various backends, so should I get it to a reasonable state somebody sufficiently enthused could probably write such a backend.
For my own goals, it'll probably be RISC-V (easy to target modern 32bit soft core "SoC"s) and WebAssembly (a passable intermediate that can be AOT'd, JIT'd, emulated, or transpiled on or for a variety of targets).

2024-04-22 04:58:29

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My big takeaway from some of this recent chatter is I should clearly be spending more of my time on my long running, slow moving, hobby language project.
My goal: a small systems language that tries to combine the joy that C has brought me over the past 3 decades with some of the syntactic and safety innovations that Go, Rust, etc have introduced, while trying to avoid the horror of modern "big compiler" UB landmines.
Because, of course, my solution is "yet another language!"

2024-04-22 04:51:58

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Are there people who seriously think "we'll never have to change again"? One of my takeaways from some of the big security oopses of the last decade or two is "we don't know what we don't know."
There's value in learning from past mistakes and trying to make the next thing a bit more resistant to breaking in the same ways that previous things broke. But that doesn't mean there won't be exciting new ways for things to break discovered in the future!
Sound like job security!

2024-04-22 04:18:26

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Yeah, teen characters to be relatable to a teen target demographic seems to be pretty typical for a lot of anime.
It's always fun to get a show with a somewhat older cast with different problems than the typical middle-school/high-school ones.
Shirobako is fun that way. Much more of a workplace comedy with the (large) main cast being variously in their mid-20s through mid-40s.

2024-04-22 01:35:19

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I've actually been surprised at how many fun shows have turned up (I had pretty low expectations).
Dungeon Meshi continues to be awesome, Hibike Euphonium is (finally) back for a 3rd season, and we get more silly camping slice-of-life in YuruCamp S3.
Meanwhile Girls Band Cry, Jellyfish Can't Swim In The Night, and Whisper Me A Love Song are all doing fun girls-in-bands slice-of-life/drama stuff.
First two episodes of Shuumatsu Train were a solid weird post-apocalyptic start, too!

2024-04-13 22:40:12

This keynote speech by [@marthawells](https://wandering.shop/@marthawells) about writing non-human intelligences and Murderbot is fantastic.
https://marthawells.dreamwidth.org/649804.html
"There are a lot of people who viewed All Systems Red as a cute robot story. Which was very weird to me, since I thought I was writing a story about slavery and personhood and bodily autonomy. But humans have always been really good at ignoring things we don't want to pay attention to. Which is also a theme in the Murderbot series."
#books #murderbot