Questions tagged [memory]
For questions about computer memory in a retrocomputing context
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Can fast page mode depend on the first data retrieved?
As early as the seventies, some computers used RAM in page mode, in which you can read two or more words from sequential locations in rapid succession by only supplying the column address once, and ...
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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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In what ways is DRAM likely to fail?
A ZX Spectrum is likely to lose the same bit of every memory address if a single DRAM chip fails completely.
However, if a DRAM chip partially fails, this could cause... interesting issues, ...
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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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How does the SAM Coupé refresh its RAM?
The SAM Coupé was a ZX Spectrum compatible computer with a 6MHz Z80, 256K RAM minimum, enhanced graphics and sound and an improved BASIC amongst other features. My question is about its memory. The ...
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When did CPUs start using page mode DRAM?
According to https://en.wikipedia.org/wiki/Dynamic_random-access_memory#Page_mode_DRAM
Page mode DRAM is a minor modification to the first-generation DRAM IC interface which improved the ...
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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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What does "Expanded Memory" mean on a Philips Videopac G7000 game?
I bought a Philips Videopac G7000 because it looks awesome. Now I need to shop for some games.
I'm interested in this AAA+ title, Crazy Chase:
However, on the box it says EXPANDED MEMORY/MEMOIRE ...
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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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Cost differential between 2 and 4 MHz RAM chips in 1982
The most common speed of the 6502 was 1 MHz, allowing the use of 2 MHz RAM chips (half the bandwidth went to the video chip to refresh the screen).
In 1982, the BBC Micro shipped, with double speeds ...
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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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RAM contention and what counts as different banks
From https://en.wikipedia.org/wiki/ZX_Spectrum_Contended_Memory
"Contended memory space, on the other hand, is shared between the ULA and the Z80 and the ULA has higher priority. Contended memory ...
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What was the first commercially available computer with ECC memory?
In the early days of computing, memory error detection and correction was either non-existent (Wikipedia tells of Seymour Cray famously saying "parity is for farmers" when asked why he left it out of ...
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How does the Apple II address more than 128KB of RAM?
For the Apple //e, it was very common to have an extended 80-column card installed which brought the machine up to 128KB of RAM via 2 banks of 64KB each. There are soft switches in the $C0xx space ...
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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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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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When did 64K RAM become about as cheap as 16K?
In the days of 8-bit computers, two of the more common memory configurations were 16K and 64K, implemented as eight RAM chips of 16kbit or 64kbit respectively. The setup was one chip per bit over the ...
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Largest ratio between base and maximum RAM
For example, the Apple II originally shipped with a base 4K of RAM but could be expanded to 48K, so the maximum was twelve times the base.
Of all the computers ever shipped, which one has had the ...
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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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ZX80 BASIC checking free memory
Did ZX80 BASIC have a way to check how much memory you were using and how much was left?
Or otherwise: if you were writing a program on a machine with the RAM expansion, was there a way to tell ...
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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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How many bits are stored in a memory location in a PDP-11?
PDP-11 is said to be word addressable, which means every data access returns 16-bit data. Suppose I give a read request for address 100 in memory. Will it return 8 bits (LSB) from address 100 and ...
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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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Memory-limited workloads
I'm trying to figure out whether computing workloads, particularly those related to science and engineering, have historically been limited by memory or CPU. (By the former, I mean not memory access ...
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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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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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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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Why does my Macintosh SE FDHD only see 2 of the 4 megabytes of RAM?
I have a whole bag of 30pin SIMMS so I thought I would see about upgrading the 1 MB of RAM in my Mac SE FDHD to 4 MB.
The original RAM had four sticks of OKI M41256A. These SIMMs have 8 chips each.
...
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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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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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How to identify size of a 30 pin SIMM (Atari 1040 STe)
I have recently acquired an Atari 1040 STe with 1MB of RAM.
I read that you can extend its RAM with 30 pin SIMM up to 4MB. But it can be done only with 256KB or 1MB SIMM, and that 2MB, 4MB, 8MB and ...
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Why are the PPU registers on the NES mirrored?
[Please see answers to this related question as well]
The NES Picture Processing Unit has eight memory-mapped registers to the CPU in registers $2000 to $2007. The are incompletely decoded, so they ...
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Where are the memory controllers for IBM 5150 or Altair 8800?
Wikipedia page for memory controller states that memory controllers are either part of the northbridge, or in more recent cases, integrated into the processor.
But AFAIK, neither IBM 5150 nor Altair ...
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Memory timings for a 430VX mainboard
I'm trying to troubleshoot a memory-detection problem on an old Pentium MMX system with a 430VX chipset. I've got the following memory timing options in the BIOS:
DRAM Precharge Wait State: 0, 1
...
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