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Questions tagged [memory]

For questions about computer memory in a retrocomputing context

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1answer
273 views

Minimal DOS long filename driver

Am trying to run Latex + Emacs under DOS 5.0, and would currently seem to need long filenames. I have tried the DOSLFN driver but it prevents Emacs from running. I have 4 MB RAM in total. Is there ...
3
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1answer
208 views

List of Intel microchips

Where could I find a list of all of the microchips released by Intel, including microprocessors, Rams, roms, storage devices. Etc. I have checked Wikipedia, and they have the processors, but not any ...
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2answers
238 views

Is it possible to upgrade original iMac (1998) memory (RAM) to above 256 MB?

I am looking into buying myself an original iMac, as I want to mess with the older system a little bit. Is it even remotely possible to change the RAM in the system to being over 256 MB? I am willing ...
8
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1answer
475 views

RAM for Socket 7 Motherboard - 64MB sticks appearing as 16MB

I hope this is the right place to ask this and that it is "retro" enough. I have a Socket 7 machine that I am working on. It's my 1st PC from childhood that I restored, and now I would like to ...
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2answers
3k views

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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7answers
9k views

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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3answers
379 views

How does memory addressing/mapping work in 8-bit systems?

If I attach a 16 KIB EEPROM to a 6502 or similar, and put some kind of operating system on it, it will run fine, but won't have access to any other chips. So, when a Commodore VIC20 had 5k of ram and ...
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2answers
2k views

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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3answers
3k views

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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2answers
176 views

What 286 chipsets support UMBs?

I read in some forums that some 286 boards support UMBs and thus can load drivers and TSRs into the upper 384 KiB of conventional memory. What chipsets support this and do I need special drivers?
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1answer
185 views

TED computers and delayed RAM chips

From 'A Company on the Edge', page 545: Commodore marketing scheduled the release of the TED computers for May 1984, but met with inevitable delays due to RAM shortages and problems with the ...
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1answer
335 views

Were 64k RAM chips $5 in 1981?

According to http://smithsonianchips.si.edu/augarten/p64.htm "In 1981, they slashed the cost of 64K RAMs from some $25 each to about $5, and the price hovered at that level throughout the following ...
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4answers
1k views

Largest practical motherboard for early computers

The power of a computer is often effectively determined by the size the RAM can be expanded to. In many cases, this was even more important than CPU speed: Memory-limited workloads In the early days, ...
6
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4answers
437 views

Early Basic memory management

Can anyone verify or correct my memory here? Long ago, I had access to a Commodore PET which I think had 8kB of memory. Also slightly less long ago, I had a Commodore 64 with its "elephatine" 64kB. ...
4
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1answer
405 views

Fastest way to write 0x00 to a zero-page memory location? (6502, Atari 2600)

I have a kernel in my 6502 game that writes two dots to a sprite, so for example: ........ ........ .XX..XX. .XX..XX. ........ ........ Either 0, 1, or 2 dots can be on at a time. This is done one ...
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4answers
391 views

What home computer was the first to use a external ROM cartridge?

When was the external ROM cartridge first used and what home computer was the first to use it?
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4answers
521 views

Columns of text in early microcomputers

As discussed in some previous questions here, 80-column text was established by IBM as the standard for business computing as early as the sixties, but monitors capable of displaying that resolution ...
4
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1answer
280 views

Is there any reason to chose ES, FS, or GS over the others in real mode?

The Wikipedia page on X86 Memory Segmentation says In real mode, the registers CS, DS, SS, and ES point to the currently used program code segment (CS), the current data segment (DS), the current ...
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6answers
649 views

Was photographic film ever used for 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 ...
6
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1answer
290 views

Repurposing the parity bit

The Nintendo 64 used RAMBUS memory, width 9 bits including parity; the latter would seem unnecessary for a console, but the machine actually uses it to store an extra bit of data. This is an unusual ...
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7answers
10k views

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 '...
5
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1answer
190 views

What kind of SIMMs can 286 PCs use?

I have a 286 Board (Octek Fox II 286) which takes up to four 30 pin SIMM modules. The manual however (http://www.minuszerodegrees.net/manuals/Octek%20-%20FOX-II%20286%20(12_16%20MHz%20versions).pdf) ...
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2answers
1k views

Unused RAM Chips on x86 machines

On classic x86 machines the upper 384 KB of system memory contains video RAM and BIOS ROM Besides other things. Those areas overlay over conventional RAM, so that you can't use all upper memory, but ...
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2answers
472 views

Is there really 1MiB of physical memory in the motherboard of a PC AT/XT?

This is a question that has been puzzling me for a while. What happens with devices like graphic cards that have their own memory chips? Do these cards read/write from their own internal memory to/...
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3answers
369 views

TSRs at top of memory conflicting with COMMAND.COM

I've seen that many TSRs installs themselves at the top of conventional memory. To do so they rely on the value at 0:413h/int 12h to tell how much conventional memory is available, and then update ...
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2answers
403 views

Is all 100% of a 64k Apple II memory usable?

Are there any areas of the 64k RAM which are permanently unusable by anything, whether by the built-in monitor ROM or user programs? Looking at $C000-C0FF, this is the "softswitch" area, and as far ...
4
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3answers
838 views

Amiga memory bandwidth

Looking at a timing diagram for the various kinds of memory access occurring on the Amiga http://amigadev.elowar.com/read/ADCD_2.1/Hardware_Manual_guide/node02D4.html it seems to be saying that video ...
7
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4answers
634 views

How did DOS know where to load itself in upper memory?

If I remember correctly, you could ask DOS to load in upper memory by writing something like... DOS=UMB ...somewhere in the CONFIG.SYS file. But the question is, how did DOS know what portions of ...
4
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2answers
133 views

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 ...
21
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2answers
3k views

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 ...
7
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1answer
177 views

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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2answers
2k views

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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1answer
362 views

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 ...
5
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2answers
665 views

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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5answers
4k views

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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1answer
249 views

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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3answers
3k views

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 ...
5
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1answer
300 views

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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5answers
1k views

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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4answers
458 views

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 ...
3
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1answer
399 views

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 ...
3
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2answers
535 views

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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5answers
2k views

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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5answers
3k views

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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2answers
747 views

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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6answers
658 views

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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3answers
1k views

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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3answers
296 views

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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2answers
772 views

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 ...
9
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1answer
257 views

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 ...