gp2000

6 ms·

1.
by gp2000 8mo ago
Well, I was pessimistic. Just pushed an update that slightly more than doubles the execution speed with a PR to the main depot pending. It is very close to 20 times faster than the original.
2.
by gp2000 9mo ago
Though it'll still be kinda slow on a Model I, I've written an about 9 times faster Z-80 code for the network evaluation. I imagine the pull request will end up in the main depot but for now you can find it in https://
3.
by gp2000 2y ago
I first heard of this in humorist Dave Barry's column. His description is worth a read. https://www.theexplodingwhale.com/evidence/resources/dave-ba...
4.
by gp2000 4y ago
And on github. I imagine it is the same as the Internet Archive copy but I have not checked. https://github.com/historicalsource/asteroids
5.
by gp2000 4y ago
It is in the sense that Radio Shack put TRS-80 as a brand on all of their computers up until the mid eighties when they started to move into PC clones. Xroar emulates the Color Computer which was known as the "TRS-80 Color Computer&qu
6.
by gp2000 4y ago
The version for the Model 3 runs on stock hardware as it shipped in 1980. It has a interrupt that fires every second vblank. Thus it is possible to get in sync with the beam but to remain in sync the program must keep track of every cycle
7.
by gp2000 4y ago
It really was a term of derision. Sure, some may have used it affectionately and even more might do so now, but by and large it wasn't used in kindness. To cite a reference, the first issue of "80 Microcomputing", a magazine
8.
by gp2000 5y ago
That isn't a bug. In the original if a guess contains a repeated letter and there is only one occurrence of that letter in the target work then the first (on the left) letter will be yellow and the second black. You can see this with
9.
by gp2000 5y ago
I imagine you're recalling this folklore.org posting: https://www.folklore.org/StoryView.py?story=Make_a_Mess,_Cle...
10.
by gp2000 6y ago
And it could also save time. The Z-80 conditional return takes 5 cycles (or "T-States" in Zilog terminology) to execute if the condition is not met and 11 cycles otherwise. Quite worthwhile in testing for uncommon cases. Consid
11.
by gp2000 6y ago
The Z-80 stack pointer (SP) is a full 16 bit register. The stack can be anywhere in memory and be as large as needed. The 6502 has only an 8 bit stack pointer which points into page 1 only (addresses 0x100 .. 0x1FF).
12.
by gp2000 6y ago
Perhaps this Vintage Space episode is video you were thinking about: https://www.youtube.com/watch?v=r5g9AglBmSI
13.
by gp2000 7y ago
The Z-80 came out in 1976, three years before the 68000 and was an extension of the 8080. I don't see comparing the two as fair or sensible.
14.
by gp2000 7y ago
Yes, enjoyable and good ideas. I feel like I've been on that "project" before. You do a bunch of work, dig into things and then discover a simple answer that, in hindsight, could have been applied immediately and made all t
15.
by gp2000 8y ago
Although it is a historical (and disavowed) footnote, the Open Text Index launched in April 1995 and sported full text indexing of web pages -- more than 6 months before Alta Vista's launch in December that year. It did serve as a back
16.
by gp2000 8y ago
You can request the documents and go photocopy them yourself at the museum. Or have their researchers do it for a fee. Just don't bother with these as they've already been done: https://www.dropbox.com/sh/yq
17.
by gp2000 8y ago
The original arcade Mortal Kombat (and MK2, MK3 and UMK3) were all written in assembly for the TMS34010 processor. No doubt ports of it to the Sega Genesis did use 68K assembler. The TMS34010 was something like a CPU and 2D graphics proces
18.
by gp2000 9y ago
The bug is explained by Dave Theurer himself in this video: https://www.youtube.com/watch?v=41TbGi7u598&t=168 Like many games at the time the code in the ROMs had tamper protection. The basic idea is to detect if the
19.
by gp2000 9y ago
I imagine the original labels would have been in English. The assembly source code I've seen for Japanese games has variables and labels in English with Japanese comments in Shift-JIS. I would guess the choice was forced because the
20.
by gp2000 9y ago
This hybrid approach was used for a series of arcade games on XArcade for the Xbox 360. Frogger, Gauntlet, Joust, Gyruss and a bunch of others. I think we referred to it as "reskinning". Mostly it was applying higher-resolution
21.
by gp2000 9y ago
Do you have a more direct link? That one just goes to Noah's home page and for the life of me I couldn't navigate to the ultra-fast math page nor find it via Google. Edit: I think I've found it: http://www.gweep.
22.
by gp2000 9y ago
Yes, for better or worse ugly is definitely a 2nd-order predictor of success. I guess "ugly" is a fair assessment of the 8086 at the time. Certainly the 68000 was a much cleaner and orthogonal architecture. On the other hand, I&
23.
by gp2000 9y ago
You could choose that the memory accesses be at any bit size from 1 to 32 with both unsigned and sign-extended register loads. In fact, I think you got to pick two sizes and for most normal operation you'd choose 16 and 32 bits. Ther
24.
by gp2000 9y ago
Emulation of that processor was a bit of a challenge. Fortunately the fully general bit addressibility was only used in gzip decompression and the drawing instructions (circles, rectangles, that sort of thing) only came up in test mode. S
25.
by gp2000 9y ago
In command contexts "." refers to the current line (e.g., :.,$s/a/b/ will perform the a -> b substitution from the current line to the last line of the file). That comes from ex which likely copied that from ed.
26.
by gp2000 10y ago
It is difficult to take a binary program and establish intent. I'd rather call these "interesting and unusual programming tricks" than "anti-emulation measures" until more evidence is presented. Mirrored memory is
27.
by gp2000 10y ago
The links to Don Hodges site are great if you want the explicit low-level details. For instance, he has a patch to fix the kill screen: http://donhodges.com/how_high_can_you_get2.htm I made a much less serious patch -- a b
28.
by gp2000 10y ago
I, too, am curious though I suspect I'm imagining worse than it is. My best guess is vitriolic raging against the modern state of technology and/or particular individuals. Though it could just as easily be sordid tales of his ex
29.
by gp2000 10y ago
I've no direct experience, but I've heard it said that "pro motion" is a successor of sorts to Deluxe Paint: http://www.cosmigo.com/promotion/index.php
30.
by gp2000 11y ago
I don't have a 6502-specific example, but scaling an image with point sampling is one place I've seen it done. The inner-loop to scale a line might look like this: frac = 0; while (len > 0) { for (frac += scale; frac

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