microprocessor emulator and assembler for mac

It's a great example of why just because most popular games can run decently with inaccurate emulators, accuracy still matters. It's actually a very good platformer, but few people have heard of it. The screenshot below is a great example of a niche game. Your aircraft has the ability to drop bombs, and this shadow acts as a sort of targeting system to determine where they will land.-something that's slightly more difficult without this seemingly minor effect.

But once you actually see it, you realize that it's quite helpful. It's easy to overlook, especially if you do not know that it is supposed to be there. But without the raster effects, your aircraft's shadow will not show up, as you see in the screenshot below. This is done using mid-scanline raster effects, which are extraordinarily resource intensive to emulate. Or consider Air Strike Patrol, where a shadow is drawn under your aircraft. Yet once you reach stage 6-1, you can quickly spot the difference between an accurate emulator and a fast one: there is a switch, required to complete the level, where the game will deadlock if a rare hardware edge case is not emulated At first glance, it appears to run fine in any emulator. This is an SNES platformer with no save functionality, and it's roughly 2-3 hours long. While it might seem unimportant, without it some games are impossible to play

What exactly is a cycle-accurate emulator?Įach emulator has a different level of accuracy.

The MAME emulator is a good example of this.Īnother important thing is cycle accuracy. It is possible to use the same 6502 CPU emulator with different interface chips and memory maps, to simulate different machines.

In the same manner, an emulator needs to place these components in the memory locations used on the original machine, as that's where the software will expect to find them. The result of this is that they wouldn't run on other machines without being rewritten. Programs would be written with explicit references to these memory locations in their code. On the Apple I, the cassette interface was at &C100, whereas on the BBC Micro it was &FE08. The rest of the memory layout is a blank canvas, and can be defined by the designer of the computer system.ĭifferent computer designers placed components in different memory locations. The bottom of the address space is used for zero-page registers and the CPU stack, so this must normally be RAM. There are some restrictions imposed by the 6502's design: on reset it looks at the top of the address space for a pointer to executable code, so this area must be ROM. This memory space is shared by RAM, program code (ROM) and all input/output (video processor, sound generator, keyboard interface, etc). The 6502's 16-bit address bus can address 65536 (64K) different memory locations.

Microprocessor emulator and assembler for mac