This is the "simpler intermediate format" I refer to in the write-up.
This helps keep the size of the emulator source down a little because, for example, the MOV instruction has a number of different encodings, and directing them all to the same piece of code in the emulator for execution saves a lot of duplicated code. These tables include things like a look-up table for the parities of 8-bit bytes (used to set the parity flag after arithmetic instructions), a table for decimal-to-BCD conversion, and (I think this is the "controversial" bit, although it really isn't that sneaky) what I call an "instruction translation" table which converts each one of the 256 possible 8-bit opcodes into another translated 8-bit opcode number, the aim of which is to group the multiple possible encodings of each instruction type (there are a total of around 94 of these) into a single "translated instruction number" (there are a total of around 53 of these). The third section is the bit referred to in the write-up as containing tables to assist the emulator doing instruction decoding.
The second section contains data also similar to a real PC BIOS, things like a translation table from keyboard scancodes to ASCII, the BIOS data area table, the initial interrupt vector table, and so on. The code starts right at the beginning of the BIOS file. You can disassemble it using an x86 disassembler of your choice to see what's going on. It's written in normal x86 assembly language, initialises the interrupt vector table and various other structures found on a real PC, loads and executes the boot sector from a disk, contains code for handling disk and video reads and writes using the normal PC interrupt interface, and that sort of thing. The first section is very much like the BIOS code in a real PC. The first section is code, the second and third are data. The BIOS binary is split up into 3 sections. I've been watching all the comments flying past and thought people might find it useful to hear about what went into the BIOS binary since there seem to be a lot of conjectures. Are you interested in promoting your own content? STOP! Read this first.įirst of all as its author it's great to see so many people playing with the emulator.For posting job listings, please visit /r/forhire or /r/jobbit.Do you have something funny to share with fellow programmers? Please take it to /r/ProgrammerHumor/.Do you have a question? Check out /r/learnprogramming, /r/cscareerquestions, or Stack Overflow.Direct links to app demos (unrelated to programming) will be removed.If there is no code in your link, it probably doesn't belong here. Just because it has a computer in it doesn't make it programming.That means no image posts, no memes, no politics.Please keep submissions on topic and of high quality.I/O − 8085 can address 2^8 = 256 I/O's, whereas 8086 can access 2^16 = 65,536 I/O's.Ĭost − The cost of 8085 is low whereas that of 8086 is high./r/programming is a reddit for discussion and news about computer programming Pipelining − 8085 doesn’t support a pipelined architecture while 8086 supports a pipelined architecture. Instruction − 8085 doesn’t have an instruction queue, whereas 8086 has an instruction queue. Memory − 8085 can access up to 64Kb, whereas 8086 can access up to 1 Mb of memory. Size − 8085 is 8-bit microprocessor, whereas 8086 is 16-bit microprocessor.Īddress Bus − 8085 has 16-bit address bus while 8086 has 20-bit address bus. Fetch Stage and Execute Stage, which improves performance.įetch stage can prefetch up to 6 bytes of instructions and stores them in the queue.Įxecute stage executes these instructions.Ĭomparison between 8085 & 8086 Microprocessor It is available in 3 versions based on the frequency of operation − It was the first 16-bit processor having 16-bit ALU, 16-bit registers, internal data bus, and 16-bit external data bus resulting in faster processing. It has an instruction queue, which is capable of storing six instruction bytes from the memory resulting in faster processing. The most prominent features of a 8086 microprocessor are as follows − Maximum mode is suitable for system having multiple processors and Minimum mode is suitable for system having a single processor. It consists of powerful instruction set, which provides operations like multiplication and division easily. It is a 16-bit Microprocessor having 20 address lines and16 data lines that provides up to 1MB storage. 8086 Microprocessor is an enhanced version of 8085Microprocessor that was designed by Intel in 1976.