Faust II
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Faust II
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I've reverse engineered the bus arbitration logic between the NEC GB-1 ET2000-based EGA card, and the Z80 that sits on the card's CMII compatibility module.
Dumping the board's three PAL decoding chips was key to figuring it all out.
It's a bit of a mess!
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💙🩷💜Ⓑⓡⓔⓣⓣ🐡🍉🐧 likes this.
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I like this detail from a company welcome email:
Your username: redacted@example.com
Your password: Just kidding, that would be terrible security.
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RE: tech.lgbt/@ShadowJonathan/1159…
This is why I'm an anarchist, actually
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Sensitive content
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dawg smartphones are fucking stupid like if you told a medieval peasant that you had a little magic brick that screamed at you for attention every few minutes they would look at you like you're an idiot and offer to kill it for you
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It’s life changing to turn off all notifications that you absolutely do not need…I would also recommend deleting social media apps off your phone and using a web browser instead.
A bit hypocritical as I’m typing this from Ivory, but I don’t find Mastodon controlling my attention. I always feel pretty deliberate about using it (notifications are also off too)
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Killing you slowly with my song
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I want to point out that several witnesses to the death of Alex Pettri have been reported to have been taken away to the Whipple ice detention facility.
That agency has no jurisdiction to hold US citizens. And I hope some set of lawyers wore the local police would be doing something about this.
Friendly reminder that you can use massgrave.dev (and audit their scripts if you don't trust to run them) to activate Windows, as well as activate Extended Security Updates (for Windows 10), and more for free, should you need to run Windows!
I absolutely do not condone doing this for a computer used in a business, as that can land you in a lot of hot water should MS bother to audit, but for personal use? Who gives a shit! Don't pay for a license!
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Stolen to add alt-text
(and to ward off my despair...)
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our stance on slop is that of sewage in wine
it only takes a teaspoon of sewage to turn an entire cask of wine into sewage
this comes with a corollary: you can pour all the wine into the sewer that you want, and it won't turn the sewage into wine
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Why aren't LLM programing workflows measurably faster when we're trying to build something well?
Programming with LLMs switches the bottleneck from development to planning, but, when building something well, planning has always been the bottleneck. 
Additionally, in normal development we're forced to take time and think over what we're making as we build it. We figure out what we want in the process of programming each small feature.
In LLM-'assisted' development we don't really have a chance think over what we're making because we're not building it. We figure out what we want through seeing the end result and repeatedly 'fixing' it.
It's like the difference between going to the basement, looking through your tools, grabbing a sledgehammer and using that to smash through a wall vs. swinging various hammer-shaped objects at the wall until you get something that works.
It's up in the air as to which will be faster, but I'd personally rather use the tool I know will work within a few swings.
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How do you know how heavy a red hot chili pepper is?
Give it a weigh, give a weigh, give it a weigh now...
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OMG IT'S HAPPENING
phys.org/news/2026-01-austrian…
In 1982, cartoonist Gary Larson published a now-iconic "Far Side" comic titled "Cow Tools." In it, a cow stands proudly beside a jumble of bizarre, useless objects that are "tools" in name only.Cell Press (Phys.org)
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gloriouscow
in reply to gloriouscow • • •#retrocomputing
Here are the equations for the primary IO decoding pal, ETIOA.
... Show more...#retrocomputing
Here are the equations for the primary IO decoding pal, ETIOA.
gloriouscow
in reply to gloriouscow • • •P19 is activated pretty much for every address, and I presume that it enables the bus data buffers.
P18-P15 are chip selects for the CRTC, Attribute Controller, Sequencer, and Graphics controller register files.
P13 is the printer port because they slapped that in there too, why not. One of the inputs to the P13 equation is dip switch 8, which disables the printer port if you hate printing.
P12 activates the CMII module - it is a OR summation of all the other selects except the printer port.
gloriouscow
in reply to gloriouscow • • •What's interesting is that P14 is an input to the individual register file chip selects. P14 is tied directly to the inverted BUSACK signal from the Z80.
That means if the Z80 has the bus, you can't write to the EGA registers - this avoids conflicts.
gloriouscow
in reply to gloriouscow • • •gloriouscow
in reply to gloriouscow • • •The PAL decoding doesn't look at anything beyond A9.
That means if accessing the CRTC registers at 3D4 is too boring for you, you can also do at at 7D4 and FD4 and so on... Impress your friends and make emulator authors hate you!
gloriouscow
in reply to gloriouscow • • •The CMII module actually takes advantage of this fact.
If you write to an EGA register but also set A10 (and A6 for a reason I haven't figured out), the CMII will know you're whispering sweet nothings in its ear.
gloriouscow
in reply to gloriouscow • • •At that point these two latches will basically compute an AND of D7 and D6.
This is a one-bit state that means the CMII card is enabled. Well, not quite yet...
gloriouscow
in reply to gloriouscow • • •Because the CMII_SEL line clocks that final D7+D6 bit into the final flip-flop that graciously allows the Z80 to run.
So to enable the CMII card, we have to write something like 0xFF to some port like 0x7C9, twice.
What do we see
CMON.COM, the utility that turns the CMII module on, actually do?gloriouscow
in reply to gloriouscow • • •gloriouscow
in reply to gloriouscow • • •gloriouscow
in reply to gloriouscow • • •The ET2000 video BIOS checks if the CMII module is active on every call to INT 10h, video services.
If it is, it punts the interrupt request to the system BIOS - every PC-compatible BIOS had to support CGA cards, because the original CGA had no BIOS chip of its own.
I was wondering if the ET2000 BIOS was going to have to duplicate every INT 10h function for CGA compatibility mode - but nah.
gloriouscow
in reply to gloriouscow • • •What's fun is that the logic to check if the CMII board is active actually passes in the affirmative sense if you don't have any of the relevant registers at all.
So trying to boot the ET2000 BIOS in MartyPC just means we ask the poor IBM BIOS to initialize a Motorola 6845 that doesn't exist and the virtual monitor loses sync.
gloriouscow
in reply to gloriouscow • • •The ET2000 has a completely undocumented register 1Ah that if you write 02h to it, apparently allows you to read whether there's a CMII card installed by reading CRTC register 12h.
That seems rather random but you do you, Tseng Labs.
They are very careful to always write 0 back to 1Ah after doing this.
The ET3000 and ET4000 chipsets seem to skip right over 1Ah, so I'm guessing this was a register that only existed on the ET2000.
It must have other bits. But what do they do??