Questions tagged [memory]
For questions about computer memory in a retrocomputing context
183
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Simple doubling of ZX80 RAM
Many moons ago when I owned a ZX80, I remember (or possibly mis-remember) seeing a simple way to double the RAM to 2K by simply piggy-backing two extra 1Kx4 chips on top of the existing two (with pin-...
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1
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420
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Did the Vic-20 save money using static RAM?
The unexpanded Vic-20 had 5K of RAM. This was quite small even by 1981 standards, but it was trying to be cheap enough for consumers to buy, and it succeeded, selling over 2 million units.
One reason ...
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3
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How did the Fairchild Channel F provide a 2K frame buffer?
The Fairchild Channel F, released in 1976, was the first modern game console, in the sense of being the first one to accept games as software, rather than just modular configuration switches.
Looking ...
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Was it possible to give an Atari 800 (not XL) 64KB of RAM?
The original Atari 800 could have up to 48K of RAM installed through the use of memory cards. When the 800XL came out, it was now possible to have up to 64K of RAM by disabling the BASIC ROM.
After ...
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How did the IBM 360 detect memory errors?
What logic did the IBM 360 use to detect, and perhaps correct, memory bit errors?
18
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1
answer
2k
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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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7
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1
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What is the motherboard part number for the Macintosh IIci that required parity memory?
This is an extension of an answer I posted years ago to the Retrocomputing question:
How did Apple fail to tap the business and scientific markets?
Most (all?) IBM PC systems required parity memory, ...
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33
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1
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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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10
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2
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585
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Why did Windows 9x allow ring-3 software to change IDT?
I was researching how old Windows 9x viruses, such as Win95.CIH, got ring 0 access, and it's shown that one of the approaches was to get the Interrupt Descriptor Table, hook the interrupt handler and ...
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27
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7
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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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29
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3
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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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How to use all memory on an IBM PC with 8086
I'm developing software for the IBM PC with an 8086 processor. I want my program to use all available memory.
I know that I can use DOS int 21h function AH=48h to allocate all available conventional ...
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3
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0
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Is it possible to corrupt a Nintendo 64 save file by turning off the console when saving to the cartridge?
All consoles with memory cards (including Nintendo 64) kept reminding you that it's very important to not turn off the power while it's saving, because this would corrupt the save file.
But for the ...
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1
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MS DOS 6.22 hangs on modern hardware after loading HIMEM.SYS
I am trying to run MS-DOS 6.22 on modern hardware. I successfully created bootable flash disk with MS-DOS 6.22. But when it starts with HIMEM.SYS enabled in CONFIG.SYS it hangs. Searching Internet the ...
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Why does the FRE() function in CBM BASIC v2 return negative values?
On Commodore machines featuring CBM BASIC v2, the FRE() function to query the amount of memory available to BASIC returns a negative number when the result exceeds 32767 bytes:
This quirk does not ...
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6
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1
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584
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How does POST memory test work on a relatively modern (2000s) PC? Does it still test every single byte like on older ones?
I have an Asus eee 4G (AMI BIOS), I want to ask if this product actually overwrites the entire RAM during cold boot. I have the "Quick boot" feature turned off and I can see the memory being ...
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4
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What did game programmers and journalists mean by a "hardware trick"? [closed]
Recently, I've been hearing a good deal about hardware tricks. For instance, the YouTuber Ahoy (see A Brief History of Graphics) mentions that some game programmers resorted to "hardware tricks&...
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0
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Did any Dreamcast VMUs/memory cards have more than 200 blocks?
Dreamcast VMUs can store 128k in 200 "blocks". Third party memory cards increased the storage by having multiple virtual cards, each with 200 blocks.
With some hacking it is possible to free ...
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2
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549
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Why are computer bus sizes integer multiples of the size of a byte, and when was that standardized? [closed]
Memory is organized in powers of two: 8 bits to a byte, then 16 bits to a short, 32 bits and so on. Some early computers did not necessarily have powers of two as their basic memory unit. When did it ...
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3
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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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5
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5k
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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 ...
7
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1
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377
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How can I resolve these intermittent memory issues?
I own a 1999 IBM Personal Computer 300GL (Type 6275-90U). It's a Slot 1 Pentium III, Intel 440BX chipset, with a riser board for adding PCI and ISA cards and 3 PC100 DIMM memory sockets.
About 50% of ...
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1
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1
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310
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GBA reading 16-bit values (or instructions) from 32-bit bus
The GBA has various memory sections (e.g. IWRAM, EWRAM, ROM, etc), each with a bus width of either 16 bits or 32 bits. To my knowledge, the ARM7TDMI lacks any cache. When the CPU fetches 16-bit values ...
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3
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656
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How can I read from a ferrite core memory today?
I need a little help navigating this ferrite core memory technology. My end goal is to use it in a calculator or something straightforward.
I understand the writing process to each core but how is ...
7
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1
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1k
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What type of memory was used in N64 and GBA cartridges?
I would like to know if consoles like the N64 and GBA used masked ROMs or some kind of eFuse based ROM, or if they were some kind or flash or EEPROM based memory. I've read that both consoles had ...
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1
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337
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When was fixed page size, flexible assignment bank switching patented?
The 8-bit microprocessors invented in the seventies, had a 16-bit address space. It didn't take long for memory demand to exceed this, with the result that bank switching was a fact of life for the ...
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5
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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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8
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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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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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votes
2
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963
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Why did third-party PlayStation memory cards forget/delete saves?
The original PlayStation did not have any writable memory, so you had to buy "memory cards" that were plugged into the front in order to save game progress.
Sony sold official cards. But ...
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11
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4
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2k
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Could the Z80 do interference-free video as the 6502 could?
Technically this isn't just about video since it applies to any regularly
scheduled DMA¹ from a non-CPU subsystem, but video is the most common
application of this technique so I'll use that as the ...
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18
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3
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6k
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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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6
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3
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How did Apple IIe software handle 64K bank switching?
The early microcomputers were well served by 8-bit CPUs with 16-bit address bus width, but later generations of these machines tended to run out of address space, and had to resort to some form of ...
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2
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2k
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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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Save state systems
With an Amiga A500, Action Replay cartridge (v1.5 or later) and memory expansion, it was possible to save a copy of the state of memory, much like a save state in an emulator. Were there any other ...
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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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How does stack size affect functioning of AmigaOS and programs?
A few weeks back I had an issue with a Python script resetting my Amiga on execution. Someone suggested to change stack size in startup-sequence to 4096. I just read that it can be set up to 2500000.
...
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1
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2
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How many kinds of mass-producible ROM is avaliable before 1970? [duplicate]
Back in the days before mask ROM (when invented?) we got core rope memories, or Little Old Ladies memories, which required lots of human labor to build.
Were there any kinds of ROMs which were ...
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2
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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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2
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496
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How many 6SN7 tubes did it take to store a bit?
One of the most important components of a computer is a circuit called a flip-flop, which has two stable states (that it can flip-flop between, hence the name); it is used for temporary storage of a ...
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43
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11
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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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Building a Memory Management Unit to expand the 16Bit Address space [closed]
I'm in the middle of making an 8Bit computer, I've selected Z80, the 20Mhz version, which is cheap and readily available. Since Z80 has a 16bit address line it can only address 64KB of memory location....
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6
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1
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Why does the VICE "load" command skip the first two bytes?
I am studying assembly of the C64, and of course using VICE to do so. VICE has the load command to load data straight into the C64 RAM. I reckoned I could use that to put machine code into RAM and run ...
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votes
1
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452
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What were the different RAM refresh techniques in the 80s
I've looked at some techniques that were used at the beginning of the eighties to refresh the RAM (CPU-based refresh for the Z80, or the use of the video circuit for computers that shared the bus ...
- 1,229
13
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4
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4k
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CPU frequency / memory wait states at end of the 80s
According to the advertisements of the late eighties, you could find RAM having an access time ranging from 120 to 80 ns (150 to 210 cycle times). A 386SX-25 could execute a typical register to ...
- 1,229
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0
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95
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How to get back from RAM1 to ROM after setting the bank bit to 1 [closed]
Mapping more than 64kb of address space
regarding cjs answer: How to get back from RAM1 to ROM after setting the bank bit to 1? the next instruction from the program counter would be read from RAM1 ...
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4
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Cheapest type of Read-Only Memory allowing Random access before Year 1970
Back in the 50s and 60s people had:
random access, read-write memories like Magnetic Cores.
sequential access, read-write memories like Delay Lines and Magnetic Tapes.
And:
sequential access, write ...
- 3,732
4
votes
2
answers
470
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How much memory does this SYM-1 have?
I have a SYM-1 with the following memory configuration:
How much memory is that? Those all appear to be L2114UCE chips, which are described as "Static 1024x4 NMOS RAM", but I'm not sure how ...
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8
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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?
- 3,141
4
votes
2
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544
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What high nibble values can you get when you read the 4 bit color memory on a C64/C128?
The C64 and the C128 have a memory for storing the color values of a character. The size of this memory is 1k x 4bit (2k x 4bit for the C128 which can do a double buffering), thus reading the value at ...
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