Questions tagged [memory]
For questions about computer memory in a retrocomputing context
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How did early laser printers get by with so little memory?
The first HP Laserjet only had 128K of 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. Obviously they were doing something clever to ...
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Why is EEPROM called ROM if it can be written to?
Is there a historical reason? Since it is rewritable it isn't read only by definition, so why call it so?
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When did computers stop checking memory on boot?
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 not visible? If not, when did it stop, and why? (Imagining ...
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Last computer not to use octets / 8-bit bytes
I am old enough to remember computers that were not octet oriented. E.g. the first that I used was an ICL 4120. It had 24 bit words which were, when necessary, divided into four 6-bit characters. ...
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Windows 98 with 2GB of RAM
I have assembled a retro-gaming PC out of an old Shuttle SN45G with a Windows 98/Windows XP dual boot.
The motherboard can handle 2GB of RAM, but apparently Windows 98 can only handle 1 GiB.
Windows ...
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Why did DOS-based Windows require HIMEM.SYS to boot?
My understanding is that all versions of Microsoft Windows that ran on top of DOS — that is, the lineage from Windows 1.0 up to Windows ME, even though the reliance on DOS diminished over time — ...
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How can you run a program that is bigger than RAM?
Suppose you have a program that is 218 words long. However you are using a 16 bit machine and have 216 words of RAM. (The RAM is directly addressed by the CPU). On the other hand, you have unlimited '...
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Did DOS zero out the BSS area when it loaded a program?
As an example, say we have a DOS MZ EXE file that's around 20 KiB in size. The EXE header contains the value 0x1400 at offset 0x0A indicating that the program is requesting 5,120 paragraphs (or 80 KiB)...
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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?
The Nintendo 64 was released in 1996. Its "Controller Pak"s, which was the name of the memory card that you put inside the controller to save the progress in certain games, require a battery ...
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How did the X-Men game for Sega Genesis have its state survive a console reset?
The Sega Genesis system had a rather interesting game. X-Men (1993) was based on the popular cartoon version of the comic book series. But it had what was still one of the most unique (and unintuitive)...
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Did anyone ever run out of stack space on the 6502?
Unlike its main rival the Z80, the 6502 had a size limit of 256 bytes for the hardware stack. That sounds like a very tight limit, but in my experience, it was never actually an issue; by the time you ...
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What is a dropfile?
After reading Charles Duffy's comment on Was there a clearly identifiable "first computer" to use or demonstrate the use of virtual memory?:
I had a computer science professor around 1999 ...
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Why was it common to reference memory locations using negative numbers on some BASICs?
If you had an Apple II, it was common in BASIC to reference memory locations above the 32K point by using a negative number. For example, if you wanted to click the speaker you would PEEK/POKE -16336 ...
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Core Memory Stability
How reliable was the ferrite ring core memory system? When the power went off, did all the magnetic positions of the iron rings in the program wire grid remain exactly as they were?
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How does the Gameboy's memory bank switching work?
I'm writing a Game Boy emulator, but I don't completely understand how its memory mapping works. Here is what I (think) I know (and don't know).
The CPU can address up to 0x10000 memory locations ...
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Why do old computers perform a long memory test on every boot?
Basically any computers from the mid 90s and earlier perform a slow memory check on every single boot. The more memory there is present, the slower that process becomes, for example: https://www....
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How did the ZX80 store both a useful program and screen memory?
I have a vague recollection from my earliest days that the ZX80 only shipped with 1K of RAM.
If this RAM was used to store both the program and the contents of the 32x24 screen, wouldn't that mean ...
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Details of video memory access arbitration in Space Invaders
I am working on an FPGA implementation of the original Space Invaders arcade machine and I'd like to implement access arbitration between the CPU and the video system. I can imagine several ways of ...
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Why was computer memory so expensive and scarce?
Computer memory used to be a limited and expensive asset for a long while (for example, in computers with 16KiB RAM or less, compared to the 2 MiB of my first PC (an Intel 486) in 1995 and current day'...
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Was it possible to write a novel on a BBC Micro 16kb/32kb memory era computer without expansions?
BBC Micro model B has 32k memory. An average book, like Mary Shelley's Frankenstein, has about 350,000 characters in it. So you'd need over 10 times the memory to load it in, plus the software to edit ...
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What were wait-states, and why was it only an issue for PCs?
PC compatibles in the 1980s were often advertised as having zero, one, two, or sometimes more "wait states". Zero wait states was the best.
Basically, the wait-states I am asking about are due to the ...
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What happened to bubble memory - is it still being sold?
At one time bubble memory was advertised as being able to store huge amounts of data in the size of a sugar cube. I don't remember what the memory density was compared to today's SD cards. What ...
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Which CPUs, if any, had an 8-bit address space?
Even the Intel 4004, which had a 4-bit word size, had a 12-bit address space. I'm wondering if any commercial CPUs had an 8-bit or similar address-space for programs, data, or both.
I'm particularly ...
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Why did BASIC programs tend to READ a redundant copy of DATA?
Take for example this BASIC version of ELIZA which starts out (in lines 50–170) by a number of READ loops which copy DATA (lines 1340 and following) into a handful of arrays.
Isn't this rather ...
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What is causing the problem with the RAM in this (claimed) Spectrum 48k?
I bought what was claimed by the seller to be an Issue 4S Spectrum 48k.
I tried loading games and some worked while others didn't. Turns out it was the 16k ones that worked and 48k didn't. This ...
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68000 and memory access speed
On the one hand, I get the impression that memory chips around 1980 could be accessed no faster than 2 MHz.
On the other hand, the 68000, introduced in 1979, had a typical clock speed of 8 MHz.
How ...
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Did any notable product use Intel's first RAM?
The 3101 SRAM was Intel's first product. At $99.50 for 64 bits, it had enough memory to store the characters expensiv. (Sorry, the final e costs extra.) Is there a record of any product using it?
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How did old computers address far more than 64K of memory despite only having a 16 bit address bus?
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 ...
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Did early assembly games use hardcoded memory locations?
In the era of C64, Apple][ GS, and SNES, did the games use hardcoded memory locations, or did they let the assembler help them (like modern assemblers)? If yes, how did they manage the memory?
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Do you need to allocate memory before you use it in MS-DOS?
In modern operating systems (for example: Windows), you can't access a memory location before you allocate that memory location to your program (or else a segmentation fault will occur).
I am ...
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Why do drives occupy memory on Amigas
I was reading this question, and it sparked an old memory. I had an Amiga 600 a long time ago. And I used to play Secrets of Monkey Island on it, great game. But then I upgraded the computer and ...
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Why did the Cray-1 have 8 parity bits per word?
According to https://en.wikipedia.org/wiki/Cray-1
The Cray-1 was built as a 64-bit system, a departure from the 7600/6600, which were 60-bit machines (a change was also planned for the 8600). ...
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How did the IBM PC handle multiple physical devices serving memory at the same physical address?
I'm trying to figure out how the IBM 5150 PC handled the case where multiple physical devices (memory chips) were mapped to the same address within the 8088's physical address space.
The closest I've ...
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Why did old consoles have special RAM dedicated for a specific task?
Even in the PlayStation/Saturn era, they had like little RAM chips which were dedicated to just "sound", or "video", or "general".
Since they still needed to have the RAM ...
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80s DRAM chips: one per bit of data bus width?
As I understand it, in the eighties the typical way of handling memory was one RAM chip per bit of data bus width. Suppose you were building a 16-bit machine and you wanted to give it 32K of RAM, you ...
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Did anyone ever put half a megabyte of memory in an Altair?
The Altair 8800 typically, at least in the early years after its release in 1975, operated with no more than a few kilobytes of memory, for the excellent and sufficient reasons that memory was ...
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Historical price of ROM
Historical price charts for RAM are quite readily available, e.g. in the mid-seventies a ballpark figure was a penny a byte. What was the price of ROM (assuming you were getting the chips produced in ...
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What did it cost the 8086 to support unaligned access?
The Intel 8086 supported unaligned loads and stores of 16-bit data, e.g. mov ax, foo was guaranteed to work even if foo was odd.
What did this cost, in terms of performance and chip area, compared to ...
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Did any computers use automatically-operated mechanical storage as electronically-read-addressable memory
From what I understand of ENIAC, it had a very large number of manually-operated rotary switches which behaved as ROM. While programming ENIAC in the early days required a plugboard, the machine was ...
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Which computers had features added purely for tax reasons?
I was recently reading about the Amstrad CPC 472, which was a CPC 464 with an extra, unusable 8KB of RAM added to avoid Spanish import fees on computers with 64KB or less.
Did any other computers have ...
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Z80 and video chip contending for random access
Back in the 8-bit days, I used 6502 computers, where the story about memory access was easy to understand. RAM chips of the late seventies and early eighties could do 2 MHz (or a bit more e.g. 2.6 in ...
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Status of brute forcing all possible memory states of a video game [closed]
For an old video game that has a small enough memory footprint, it should be possible on exponentially larger modern systems to create a graph of all possible states of memory and the inputs that ...
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Was photographic film ever used for digital data storage?
I was thinking about how Williams Tubes worked and how one could hypothetically "snapshot" (quite literally!) the state of a computer's memory by simply taking a photograph of the phosphor end of a ...
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Could a Z80 address a total of 128 KB of ROM and RAM?
In a nutshell, could the Z80 address 64 KB of ROM and 64 KB of RAM, or just 64 KB for both RAM and ROM?
Unfortunately, I couldn't find an exact and a direct answer to my question while searching. ...
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What happened to ZIP RAM?
I have several retro machines and add-on cards for the Amiga that use ZIP RAM. This vertically mounted chip design enjoyed a brief popularity in the early 1990s, in between the original DIP DRAM and ...
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Speed of early ROM versus RAM chips
In the late seventies, up through around 1981, the maximum access speed of off-the-shelf RAM chips was around 2.6 MHz.
Did the same speed limit apply to ROM chips of the same era? If not, what would ...
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Can a 16K computer be upgraded to 64K?
A slightly odd question, but is it possible to take an old 16K computer that wasn't designed for memory upgrades, such as a Commodore 16 or PET 4016, and upgrade it to 64K as a hardware hack?
I'm not ...
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Under what circumstances would RAM locations 0 and 1 be written and/or read on the C64?
To be clear, I'm talking about the actual memory cells at addresses
$0000 and $0001 in the DRAM chips. Devices can of course initiate read
or write requests to these address on the address/data buses ...
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What was the design of the Macintosh II's MMU replacement?
I am in the process of repairing a Macintosh II and trying to understand the design rationale behind Apple's MMU replacement part installed in this machine.
As you can see in the picture, there is a ...
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What manages Upper Memory Blocks (UMBs) in MS-DOS?
I had always assumed that EMM386.EXE was responsible for managing the Upper Memory Blocks - UMBs - the memory space between 640KiB and 1MiB in real mode x86. For example, on MS-DOS 6.22, help emm386....
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