RetroSpark

9 ms·

1.
by RetroSpark 11mo ago
You're right: many of TecToy's Brazil-exclusive Master System games were tweaked versions of Game Gear releases. That includes games like Ecco 2, Mortal Kombat 3 and Sonic Blast, but not the aforementioned Street Fighter II which
2.
by RetroSpark 1y ago
I don't know if they even had an emulator at the time - I don't think a 1980s PC could run a NES emulator at a reasonable speed. Another possibility is that they used a hardware device. Perhaps something that watches the 6502 `syn
3.
by RetroSpark 1y ago
> On execution, 16-bit Thumb instructions are transparently decompressed to full 32-bit ARM instructions in real time, without performance loss. That quote is from the ARM7TDMI manual - the CPU used in the Game Boy Advance, for example
4.
by RetroSpark 1y ago
Throughout the entire NES game library, almost no games use these illegal opcodes. Apparently as part of the licensing process, Nintendo would verify that games only used the official instructions. I wonder how they tested that, though? I d
5.
by RetroSpark 2y ago
> Link's Awakening feels like it shouldn't be possible in a single megabyte of mask ROM Half a megabyte, even! (For the original monochrome game - the later color version is a full megabyte.)
6.
by RetroSpark 2y ago
220uF is correct. Along with the 75Ω terminating resistor inside the TV, that forms a high-pass filter with a cutoff frequency of ~10Hz.
7.
by RetroSpark 2y ago
Nice and compact! When I was writing a Z80 emulator I made heavy use of the tables in Sean Young's "The Undocumented Z80 Documented" [0] (chapters 8, 9 & 10). This 2-page reference card seems to contain just about everyth
8.
by RetroSpark 2y ago
> no instruction timing chart? Instruction timings are in the pink table on the left-hand side. For example, `ADC HL, BC; ED4A; H15` means that the instruction affects the flags as in row H and takes 15 cycles to execute.
9.
by RetroSpark 2y ago
> Sony’s part number suggests it has a 45 inch tube inside. But in a rare case of truth in advertising, Sony advertised it as a 43-inch model. The overall tube size is 45”, the actual screen size is 43”. I believe it was mandatory in t
10.
by RetroSpark 2y ago
According to [0], about 1.2 kg (2.6 lbs). Surprisingly this is mostly in the neck and funnel of the tube - the screen itself uses different metals because lead would affect its optical performance. [0] https://www.sciencedirect.c
11.
by RetroSpark 2y ago
Yes, the aperture grille (hundreds of wires and a metal frame holding them in tension) is itself heavier than a traditional shadow mask. However, aperture grilles also use differently-shaped glass from shadow masks. The screens are only cur
12.
by RetroSpark 5y ago
AFAIK the French NES is just a PAL console with an added composite-to-RGB converter. Although it outputs RGB signals, the quality is no better than composite.
13.
by RetroSpark 5y ago
The Sega Genesis did something similar - its hardware is a strict superset of the Master System's, so it can run SMS games natively. However, unlike the Game Boy and GBA, the cartridge ports on the two systems are physically different
14.
by RetroSpark 5y ago
> A megabyte of ram on a machine with only a 16 bit address space gets a bit silly. Do you really want to manage 16 memory pages? The Game Boy Color has a 16-bit address space and almost all its games are 1MB or larger (although that
15.
by RetroSpark 5y ago
https://en.wikipedia.org/wiki/SuperGun
16.
by RetroSpark 5y ago
It doesn't sound like they include the entire ROM, only the parts necessary to play back the recording. If you "take control", the game may try to access parts of the ROM which are missing, which causes the quote to reset. Th
17.
by RetroSpark 5y ago
Presumably this refers to Ricoh, who produced the CPUs and PPUs for both the NES and Super NES.
18.
by RetroSpark 5y ago
The Game Boy is much more similar to the Sega Master System & Game Gear than to the NES. Some games (e.g. Lemmings 2, Pinball Dreams, Spirou) were developed for both handhelds (or even for all 3 platforms) using a single assembly-langua
19.
by RetroSpark 5y ago
> In reality, every monitor was a CRT. They just drew what looked good on their development devices. True, but there was a huge difference between a good-quality RGB monitor and a consumer TV connected via composite video or RF. Ideall
20.
by RetroSpark 5y ago
> a 32x20 array of tile indices Oops, that should say 32x 30 .
21.
by RetroSpark 5y ago
> The graphics chip can halt the CPU until it has reached the start of a new scanline. This seems similar to the horizontal-blank interrupt that's available on later machines, where it's widely used to change color palette or
22.
by RetroSpark 5y ago
> The NES didn't have a framebuffer either The NES does have two nametables that perform a similar role, though. Instead of storing a 256x240 array of pixels, they store a 32x20 array of tile indices, each describing an 8x8 pixel
23.
by RetroSpark 6y ago
The other replies describe the lack of coprocessors, but there is one way in which Mega Drive cartridges got more sophisticated over time - increased ROM capacity. At launch, most games were around 512KB in size. By the end of the machine&#
24.
by RetroSpark 6y ago
I assume the suggestion isn't that Nintendo should give the games away. Just that if you buy a game on the Switch you shouldn't have to buy it again when you upgrade to their next console.
25.
by RetroSpark 6y ago
> It’s a shame that for most classic games, the source code will never be released. I wish that after a while, and things were no longer commercially viable, code would be released. Unfortunately, many game companies lost the source co
26.
by RetroSpark 7y ago
I used a debugger - it looks like the function in the DMA registers is actually just 32 bits : $4317 mvn src,dest $431a rts Each of `src` and `dest` is either $7e or $7f, so this code performs a RAM-to-RAM memcpy.
27.
by RetroSpark 7y ago
That's right. Sorry if it wasn't clear.
28.
by RetroSpark 7y ago
"The DMA registers [...] run the full CPU 3.6Mhz speed. [...] I put a 32 byte function that would draw a scanline of polygon data in there." The SNES supports SlowROM and FastROM but, interestingly, its internal memory is "Sl
29.
by RetroSpark 7y ago
This. The Super NES memory map is divided into 256 banks of 64KB each. The bottom 8KB of RAM is visible in 128 of these banks, but the remaining 120KB only appears once. The bottom 8KB of RAM is therefore faster to access (at any time, it&#
30.
by RetroSpark 7y ago
It's more like a cut-down Z80. Some registers are missing (note the list excludes IX and IY), as are some instructions (but a few others are added) and even some of the status flags. The official name of the CPU is unknown - there&#x27

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