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Why is EEPROM called ROM if it can be written to?

Look at the development: ROM = read-only memory = can only be read when on the board, programmed in the chip factory. PROM = programmable read-only memory = can be programmed with a special programmer,...
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53 votes
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Why was it common to reference memory locations using negative numbers on some BASICs?

The difference between Applesoft BASIC and the other Microsoft 6502 BASIC derivatives can be explained by the fact that Applesoft BASIC was not the first BASIC for the Apple II; the first was Apple II ...
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47 votes
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When did computers stop checking memory on boot?

When did computers stop checking memory on boot? Never. I remember my old 8088 used to do this (640K OK) but can't remember seeing anything like this since. Does this still happen and it's just ...
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44 votes
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Could a Z80 address a total of 128 KB of ROM and RAM?

The Z80 has an address space of 64KB. That means it can perform 8 bit reads or writes to 65,536 distinct locations as specified by the 16 address pins on the CPU. As far as the Z80 is concerned that's ...
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44 votes
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Did any notable product use Intel's first RAM?

It might be important to know that the 3101 was neither a genuine Intel development, nor intended as a RAM - at least not in a way we see RAM today. After all, what use could there be in 1970 for a ...
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44 votes
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Why was computer memory so expensive and scarce?

As noted in some initial comments (but I feel fine answering, as I had the exact same ideas when I read the question), this is a general progression of technology but there are two very specific ...
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42 votes

Was it possible to write a novel on a BBC Micro 16kb/32kb memory era computer without expansions?

You just made a file for each chapter, like sensible people do with current word processing! It is very unusual to write something lengthy in a single document.
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42 votes

How did early laser printers get by with so little memory?

To print an area of 7.5 by 10 inches at 300 DPI requires 844K if it's kept as a single bitmapped image. Does it? Maybe. Then again one cold think of many simple ways (like RLL) to compress a rendered ...
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42 votes
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Why did Nintendo 64 (1996) memory cards require a battery inside them to retain data whereas the PlayStation (1994) ones did not?

Most likely different acrchitecture comes from idea how memory cards will/should be used and what are the available interfaces to access them. The PS memory cards do have flash memory, but the bus to ...
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36 votes
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How can you run a program that is bigger than RAM?

The method depends on whether you have the address space or not, regardless of the RAM limitation. If you already have a 32-bit address space, but simply not much RAM, then the answer is virtual ...
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35 votes
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Last computer not to use octets / 8-bit bytes

In the early 1990's CDC sold a line of Cyber 180 mainframes. These machines were descendants of the CDC 6600 and supported that machine's 60-bit word size and 6-bit characters. Notably, one of the ...
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35 votes
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How did the ZX80 store both a useful program and screen memory?

Both the ZX80 and the ZX81 had a variable-size display file (DFILE). They didn't store the complete screen contents, but rather only the characters per line up to a terminating newline. This ...
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34 votes

What is a dropfile?

TL;DR; Dropfiles are somewhat related to virtualization as they allow to remove a process complete from execution and restart it later. Agent_L describes it quite head on as 'per-process hibernation'. ...
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31 votes

Do you need to allocate memory before you use it in MS-DOS?

The basic answer is “yes”, assuming you want to be a good DOS citizen, however in many cases you don’t need to worry about it because the operating system takes care of it for you. If you’re talking ...
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31 votes
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Why do old computers perform a long memory test on every boot?

Why are they doing that? The most important reason is that IBM introduced that check as part of the BIOS startup code, so everyone copied it to be compatible. The PC did differ from many other ...
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31 votes

Why is EEPROM called ROM if it can be written to?

EEPROM can't be "written to." It can be programmed. Programming is different. When there's EEPROM in a CPU's physical address space, ordinary write cycles will not affect it. Something out ...
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30 votes
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How did old computers address far more than 64K of memory despite only having a 16 bit address bus?

I don't know details of the Sharp PC-G830 specifically but the technique used to address more than 64K with a 16-bit address bus is called "bank switching". This involves setting up some ...
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29 votes

68000 and memory access speed

If you look at the datasheet of a typical DRAM chip of this era, say the Mostek 4116, it indeed has a cycle time of 375ns, so you can't access it at more than 2.6 MHz. But don't confuse the clock ...
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29 votes

Core Memory Stability

Caveat: I can only tell about mainframes. Minis might have used different protection and handling schemes (and for sure smaller memory sizes). My detailed knowledge is based on memory up to the mid-...
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29 votes
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Why did the Cray-1 have 8 parity bits per word?

There were 64 data bits and 8 check bits. It seems to me by the nature of parity, it should suffice to have one bit of overhead per word, rather than eight. [...] What you refer to here is a simple ...
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  • 168k
28 votes

Last computer not to use octets / 8-bit bytes

Unisys continued shipping 36-bit systems far more recently than 1997. The last new 36-bit Dorado - the 800 series -- was released in 2011, and superseded - per my recollection - by the Xeon-based, ...
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28 votes
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How does the Gameboy's memory bank switching work?

ROM and RAM bank switching is controlled by a memory bank controller present on the cartridge. By writing values to areas of read-only memory, a game or program is able to specify which ROM banks to ...
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28 votes
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Which CPUs, if any, had an 8-bit address space?

PIC: 7 bit address space The Microchip PIC family of CPUs specifically the 10, 12 and 16 series have 7 bits of address space. While 7 bits is not exactly 8 bits this shows that there are commercial ...
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27 votes

What is causing the problem with the RAM in this (claimed) Spectrum 48k?

A single bad DRAM, probably — in machines of that vintage each DRAM holds only a single bit at each address; you use eight in parallel to serve an 8-bit bus. And the Spectrum uses physically separate ...
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27 votes

Why was computer memory so expensive and scarce?

I'm mostly concerned about RAM. Why was it so expensive? It wasn't - at least not once integrated circuit RAM became available in the 1970s. Compared to other chips, RAM was cheaper both per ...
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26 votes

How did early laser printers get by with so little memory?

In addition to Raffzahn's usual excellent answer, a few important things to note: PCL still exists. You can (I do...) still write software that sends simple PCL commands to a printer to select fonts, ...
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26 votes

Why do drives occupy memory on Amigas

You use the Amiga DOS ADDBUFFERS command to add (or remove) the configurable buffers for your drives. ADDBUFFERS adds buffers to the list of buffers available for a drive. Although adding buffers ...
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26 votes
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Did anyone ever put half a megabyte of memory in an Altair?

Did anyone ever put that much memory in an Altair, IMSAI or other 8080/Z80 S-100 bus machine? Has been done a lot of times. Remember, S100 has been used all the way thru the 1980s into the 1990s. RAM ...
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25 votes
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Windows 98 with 2GB of RAM

I might have found a stable way to limit Windows 98 to use only 1 GiB of RAM with HimemX: Install Windows 98 with 1 GiB of RAM or less; Download himemxfrom https://sourceforge.net/projects/himemx/; ...
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