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Is there was any microprocessor older than Intel 8086 (e.g., Z80, Intel 8080) which can run The Microsoft Windows 1.0 and at least display the GUI without glitches? Also, using software mods, binary ...
JOrE's user avatar
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In a summary of the history of the DWARF debug info format, the claim is made that "fatal flaws were discovered in Motorola's 88000 microprocessor". After googling and looking in Wikipedia, ...
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Computers can work with as little as 1 bit of data at a time, have only 1 instruction, and 1-bit RAM was once common. A big step up, 4-bit architectures were very versatile, including the famous Intel ...
Therac's user avatar
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As I was skimming through an old MS-DOS game's README, I stumbled upon this: Therefore, we reccomend a newer 486-100 or better, preferably with a large external cache. Best performance will result ...
aybe's user avatar
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A key objective of RISC-V was that every aspect of the ISA must be based on an expired patent. It was felt that this is the only truly reliable defense against patent lawsuits. It is surprising that ...
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What was the reason Texas Instruments indexed bit names (of data bus, address bus, registers) in the TMS99xx family (e.g. TMS9900, TMS9995) from MSBit (=bit0) to LSBit (=bit15) instead of the other ...
Curd's user avatar
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I am reading Computer Organization and Architecture, 10th ed. by William Stallings and I found this on page 26. where it says the addressable memory of 4004 is 640 bytes. But it appears that the ...
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The Z8000 was Zilog's entry in the 16-bit microprocessor market; it was unsuccessful in large part, as I understand it, because it took too long to debug. According to https://thechipletter.substack....
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I've started using my Soviet Mikrolab KR580IK80 (a clone of the Hewlett Packard 5036A) again, and I've noticed some behaviour which it used to exhibit but now it seems more frequent. Basically after ...
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Starting in the late seventies, the microchip industry generally switched from NMOS to CMOS, primarily because CMOS circuits use less power, though they also have other advantages like more noise ...
rwallace's user avatar
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6 answers
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The ARM-1 was an early RISC CPU, designed in 1986 (and even more typical of early RISC design constraints than the year would suggest, since Acorn didn't have the budget to pay for the latest process ...
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In UK secondary education, there's a model called the fetch-execute cycle, which describes how computers work. (See: Isaac CS; Bitesize GCSE, Higher; Teach CS.) As I understand it: The processor has ...
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Were there any enhancement chips in officially-released games that were CPUs themselves and which ran the game code itself, relegating the role of the main CPU to that of a thin client? To elaborate, ...
forest's user avatar
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I have an old Sharp PC-G830 pocket computer from the '80s that has 32K of RAM and 256K of ROM. I also have a simple single board computer I built with 128K of RAM and a few megabytes of ROM from a ...
Shades's user avatar
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How does the technology keep improving despite having everything discovered already? I mean the same sized chips and electronics are used from year to year but with every new version of the main board ...
Borislav Stefanov's user avatar
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Last summer, the Itanium has finally been discontinued, twenty years after its release. It was a promising technology, but in the end it turned out to not really be the case. Beside a few niche ...
aybe's user avatar
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I've been working on the NatSemi PACE article and I'm trying to track down a bit of trivia... someone inserted a statement: McDonnell Douglas produced a classified military 16-bit processor called ...
Maury Markowitz's user avatar
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(I'm assuming a memory cycle of 500 ns, without wait states.) According to the 68000 bus diagram, there are 4 CPU cycles for a memory cycle, so an external frequency of 8 MHz. However, things are ...
airman's user avatar
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I've read that Z3, first electromechanical general purpose computer operated at a frequency of about 5–10 Hz, and the ENIAC had a 100 kHz clock, though each instruction took 20 cycles. What ...
alessandro's user avatar
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Early microprocessors often used NMOS or PMOS transistor technology (see this question for their use in early Intel chips). Techniques such as implementing registers with dynamic memory cells (...
DrSheldon's user avatar
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I have an instruction: ADD [BX][SI] + 5FFDH, EABFH and I want to know how it operates exactly on 8086 microprocessors. I've realized that this instruction ADD [BX][SI] + 5FFDH, EABFH, works in this ...
user3866081's user avatar
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So, first off, I am kind of a noob with emulators and the 6502. Summarise the problem If we for example take the instruction ADC Immediate ($69) which adds the accumulator to an immediate value and ...
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Modern out of order CPUs can do all sorts of things in parallel, having not only multiple functional units, but a lot of logic to check at runtime exactly which instructions really depend on others, ...
rwallace's user avatar
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The Intel 8086 CPU could address up to 1 MB of memory using segmentation, and this CPU have 4 segment registers, which are CS and SS and DS and ES. Each segment in memory can have a maximum size of 64 ...
Asra Zibaie's user avatar
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I have the following assembly code for 8086 MOV AL, [BX] OUT DX, AL The bus clock frequency is 1MHz. Access to memory is done without WAIT, and to I/O with one WAIT tick. How I can calculate the ...
gameloverr2's user avatar
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1 answer
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The Intel 4004 used MOS (metal–oxide–semiconductor) transistors. What has been the transistor types used in Intel processors onwards from the 4004 to 8085 to the x86 family of instruction set ...
Single Malt's user avatar
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Datasheet for the Intel 8008 CPU mentions that the Carry (C) flag is affected with the logic operations (AND, OR, XOR), but it does not make any sense. I believe Carry will be zeroed, but I have no ...
Martin Maly's user avatar
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3 votes
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Intel 8008 CPU has an internal stack, implemented as an 8 x 14-bit scratchpad. How does it work exactly? Is there any "invisible 3-bit stack pointer"? I want to know what happens when the ...
Martin Maly's user avatar
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8 votes
0 answers
364 views

What happens when I8008 CPU reads the "undefined" opcode (22h, 2Ah, 32h, 38h, 39h, 3Ah; or in octal 042, 052, 062, 070, 071, and 072)? Are these opcodes evaluated as a NOP instruction, or ...
Martin Maly's user avatar
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9 votes
4 answers
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If you look at a die photo of a 6502, about forty percent of the chip is taken up by what's obviously microcode, both by its regular structure and by the obvious need for such from the instruction set,...
rwallace's user avatar
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49 votes
2 answers
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The 80486 processor can execute many instructions in a single cycle, such as a register-to-register add instruction (ADD EAX, EBX, for example), which one would generally assume is fairly complex, ...
occipita's user avatar
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25 votes
4 answers
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In his June 1985 foreword to Programming the 65816 by David Eyes and Ron Lichty, Bill Mensch expresses his hopes for a 6502-derived 32-bit microprocessor: the 65832. WDC is still thriving, but the ‘...
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I was reading about the SAP computers(as I do), and examined the SAP-2 chapter of Paul Malvino's Digital Computer Electronics, hoping to learn about how a microprocessor without a multiply instruction ...
Nip Dip's user avatar
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1 answer
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Im trying to get some nice colored lines on some old Z80 system synced to the PAL screen, but having some sort of a problem. First I just need to know if my facts are right. I know that on Commodore ...
Natural Number Guy's user avatar
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3 votes
2 answers
441 views

I remember reading somewhere (maybe on Hacker News or Lobsters) that Motorola made a microprocessor some decades ago with two sets of registers. This means when handling an interrupt, it does not need ...
nalzok's user avatar
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95 votes
10 answers
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The DEC Alpha, released in 1992, seems like an early implementation of a fully 64-bit microprocessor architecture. Its release led to quite a bit of both marketing hype and genuine vendor support in ...
Brian H's user avatar
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1 answer
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I already know that the maximum integers for ranges higher than 24-bit (16 777 216) will very likely exceed 1 000 000 000, so, what is the maximum 64 bit integer? It is larger than 10 bilion?
hinamuyatutama's user avatar
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41 votes
15 answers
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After seeing this question, I was struck with an intense curiosity to know: Were there ever processors with word sizes that aren't powers of two, specifically after the 8-bit byte became the industry ...
Hearth's user avatar
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2 answers
718 views

Having only a single index register and no addressing mode indexing against 16-bit addresses in memory seems to have been widely considered a primary reason that the Motorola 6800 fared poorly in ...
cjs's user avatar
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3 votes
3 answers
675 views

I have a really basic question. I have to design an 65C02-based personal computer for a school project. I have to draw my own footprint for the 65C02. My question is what type of pin is the IRQB (...
ZaharyMomchilov's user avatar
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10 votes
3 answers
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The Nintendo Game Boy has RAM called "HRAM" (meaning "high ram") decoded at locations $ff80 through $fffe. (All other decoded locations in the $ffxx page appear to be I/O device and system control ...
cjs's user avatar
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6 votes
1 answer
453 views

I see many references to a paper by Andrew Tanenbaum that demonstrated the vast majority of constants would fit into 13-bits, and I seem to recall it being in my university text on CPU design. However,...
Maury Markowitz's user avatar
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I'm trying to make a 6502 replica in Logisim. I want to know what exactly each control signal in 6502, how the clock cycles work and additionally I would like to see an example of these control ...
Senijs's user avatar
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3 votes
2 answers
707 views

What's a good way to estimate the total number of 6502 or 8051 chips (or workalikes, pin-compatible or not, but not including software or FPGA emulators) ever manufactured or sold? Added: (To ...
hotpaw2's user avatar
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Virtual memory, which allows an operating system to run several machine code programs isolated from each other, came to the desktop during the eighties. But full virtualization, which lets the ...
rwallace's user avatar
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18 votes
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To my knowledge, an emulator turns machine code for a console into something that your computer can understand. For example, assembly code from a Gamecube game is not the same as from a .exe file. ...
Jonathan O'Brady's user avatar
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3 votes
1 answer
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What are the features of the Intel 8051 architecture that allow it to successfully act as a microcontroller? Hypothetically can the general-purpose 8-bit architecture like Intel 8080 do everything the ...
Jet Blue's user avatar
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16 votes
2 answers
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This question expands on How does the 6502 implement its branch instructions? I'm working on a cycle accurate VHDL implementation on an FPGA. I have much of the program logic already written, but I ...
Evan's user avatar
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22 votes
8 answers
13k views

What was the halt instruction in early CPUs such as the Z80 and 8080 used for? Here's a description of the Z80 instruction: The HALT instruction suspends CPU operation until a interrupt or reset is ...
Jet Blue's user avatar
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31 votes
5 answers
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How was microcode implemented in retro processors such as the Z80 or 8080? Was the microcode standard (for example a manual for the processor outlining all possible micro-instructions and the ...
Jet Blue's user avatar
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