Viewing profile — rep_lodsb

Why should AI enthusiasts expect logical reasoning? AI "reasoning" is the model babbling to itself, using statistically likely sequences of words that appear in the training data. …

8080 assembly language makes it easy to understand what the restrictions are. Z80 much less so. Much of the instruction set was carried over from the 8008, that's where you get MOV…

And for you that's reason enough not to watch his videos? Fine, but I get the distinct impression you (and other people in your "camp") don't want anyone else to watch his content …

16-color EGA and VGA had separate bitplanes, so writing 4 monochrome images would take the same time as a single one in color.

That's a limitation of the Turbo C library, as the comment says. DOS memory allocation functions take the size in 16-byte "paragraphs", and return a segment, with the allocated mem…

A lot of that is just bloat that you wouldn't have had back then. But it could still be handled by an 8086, not by storing the raw HTML in memory at all, but parsing it as it loads…

Well, one indication is the value loaded into EDX on reset: 9B5 BIST1 -> TMPD 0x0303 PASS2 9B6 SIGMA -> EDX 9B7 BIST2 -> TMPE TMPD XOR 9B8 SIGMA 0x3ddc0c2c XOR 9B9 SIGMA -> EAX BOO…

Maybe websites should work without loading megabytes of scripts from third-party servers? I think that should be disabled unless you opt-in. Also browsers by default using a blockl…

Something like uMatrix should be built right into the browser, and the fact that this isn't the case really says it all about how it's not the "user agent" anymore. It's the one ex…

Slight correction, the correct offset is 7, and DAA only adds 6. But the trick is also adding the carry bit. This works on the 6502 in decimal mode too, e.g. https://news.ycombinat…

I know this comment will get ignored by the true believers, and likely pasted directly into Claude by the author in order to "further improve" the code, but here's some small excer…

Fun fact: "/dev/nul" (with only one L) would have worked, even if there is no directory with that name. That's been a feature since DOS 2.0, there was even an undocumented option A…

Last I checked, it's still mostly unusable, especially on real hardware (both modern and Win2k-era). Not saying this because I have anything against it, that's just a fact. Of cour…

The original code using ROL should have been correct? As I see it, what is needed is a rotation without involving the carry flag, and the fix emulates that by RCL'ing the two bits …

Division by zero is handled the same on x86, and also changed from "trap" to "fault" after the original 8086/8088. And despite what is often said about its variable-length instruct…

Most of mul/div was implemented in hardware since the 80186 (and the more or less compatible NEC V30 too). The microcode only loaded the operands into internal ALU registers, and d…

That's greatly oversimplified, or less generously, just flat out wrong. Win32 programs have always had their own isolated address space. That infamous BSOD is the result of memory …

I don't doubt that this specific processor special-cased XOR (regardless of how it was called in the assembly language)! Merely pointing out that where both operations were availab…

These two steps usually run in parallel though, with transistors to enable them depending on what operation should be performed.

Some other architectures like PDP-11 and 680x0 had a dedicated "clear register" instruction. It could have been added to x86, even as a group of single-byte opcodes with the regist…

Interesting, since the general culture at IBM seems to have preferred SUB over XOR -- their earlier business-oriented machines didn't even have a XOR instruction, and even on later…

Comparing for equality can use either SUB or XOR: it sets the zero flag if (and only if) the two values are equal. That's why JE/JNE (jump if equal/not equal) is an alias for JZ/JN…

Yes, the far jump was never necessary on any processor, only a convention. You can stay in the same segment as in real mode and it will continue to work. But some kind of control t…

Well, Intel documented that the very first instruction after enabling protected mode had to be an "intra-segment" ( not inter-segment ) jump, to flush the prefetch queue. At least …