Questions tagged [memory]

For questions about computer memory in a retrocomputing context

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Did anyone use quarter-bad RAM chips?

There was a time in the early 80s when 64k RAM chips had a significant defect rate, such that half-bad ones could be obtained at a discount. Some computer manufacturers such as Sinclair and Tandy took ...
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20 votes
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Did 486 SMP systems provide Total Store Ordering?

Cache-coherent SMP (symmetric, or shared-memory, multi processing) systems can provide various grades of memory ordering guarantees, the stronger ones being more expensive but making it easier to ...
rwallace's user avatar
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23 votes
3 answers
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Did any x86 CPU optionally trap unaligned access?

x86 CPUs have always supported unaligned load/store. Early RISC CPUs didn't. So imagine writing portable code on a 386. It seems to work fine, but how do you know you haven't accidentally misaligned ...
rwallace's user avatar
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8 votes
1 answer
989 views

Did any 8-bit computers use 16kx4 RAM chips?

An 8-bit computer wanting 64K of RAM, could most straightforwardly use eight 64kx1 DRAM chips (64kbit, 1 data line). The Commodore 64 initially did this, but in the mid-80s, the cost-reduced redesign ...
rwallace's user avatar
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13 votes
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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-...
paxdiablo's user avatar
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9 votes
1 answer
457 views

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 ...
rwallace's user avatar
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13 votes
3 answers
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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 ...
rwallace's user avatar
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9 votes
2 answers
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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 ...
bjb's user avatar
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8 votes
2 answers
1k views

How did the IBM 360 detect memory errors?

What logic did the IBM 360 use to detect, and perhaps correct, memory bit errors?
Will Octagon Gibson's user avatar
18 votes
1 answer
2k views

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 ...
rwallace's user avatar
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7 votes
1 answer
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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, ...
Dale Mahalko's user avatar
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35 votes
3 answers
5k views

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 — ...
mkay's user avatar
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10 votes
2 answers
626 views

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 ...
Ilia Ershov's user avatar
27 votes
7 answers
7k views

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 ...
rwallace's user avatar
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31 votes
4 answers
5k views

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)...
Machavity's user avatar
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10 votes
2 answers
2k views

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 ...
pts's user avatar
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3 votes
0 answers
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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 ...
Domoni's user avatar
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5 votes
1 answer
1k views

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 ...
Art Spasky's user avatar
13 votes
2 answers
729 views

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 ...
Psychonaut's user avatar
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6 votes
1 answer
627 views

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 ...
Hasbo's user avatar
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3 votes
4 answers
2k views

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&...
AndrewGreen's user avatar
3 votes
0 answers
246 views

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 ...
user's user avatar
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1 vote
2 answers
599 views

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 ...
Michael Stachowsky's user avatar
17 votes
3 answers
4k views

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 ...
TomKern's user avatar
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18 votes
5 answers
5k views

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 ...
Supernintendo Chalmers's user avatar
7 votes
1 answer
387 views

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 ...
Brian Reading's user avatar
1 vote
1 answer
341 views

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 ...
Mona the Monad's user avatar
12 votes
3 answers
706 views

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 ...
Timothy Szymanski's user avatar
7 votes
1 answer
1k views

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 ...
Chris_F's user avatar
  • 173
2 votes
1 answer
341 views

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 ...
rwallace's user avatar
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21 votes
5 answers
4k views

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 ...
Shades's user avatar
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24 votes
8 answers
8k views

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'...
Piovezan's user avatar
  • 421
30 votes
1 answer
7k views

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 ...
Jacon's user avatar
  • 303
5 votes
2 answers
1k views

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 ...
Riddick's user avatar
  • 51
11 votes
4 answers
2k views

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 ...
cjs's user avatar
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18 votes
3 answers
6k views

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 ...
rwallace's user avatar
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6 votes
3 answers
989 views

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 ...
rwallace's user avatar
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19 votes
2 answers
2k views

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 ...
Omar and Lorraine's user avatar
5 votes
5 answers
622 views

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 ...
Sam's user avatar
  • 421
22 votes
10 answers
5k views

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 ...
natevw's user avatar
  • 2,937
4 votes
1 answer
683 views

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. ...
Bartek Malysz's user avatar
1 vote
2 answers
191 views

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 ...
Schezuk's user avatar
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20 votes
2 answers
4k views

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?
DrSheldon's user avatar
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5 votes
2 answers
519 views

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 ...
rwallace's user avatar
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43 votes
11 answers
8k views

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 ...
Mark Ransom's user avatar
4 votes
1 answer
964 views

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....
ilgaar's user avatar
  • 141
6 votes
1 answer
755 views

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 ...
Bart Friederichs's user avatar
5 votes
1 answer
485 views

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 ...
airman's user avatar
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13 votes
4 answers
4k views

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 ...
airman's user avatar
  • 1,350
2 votes
0 answers
96 views

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 ...
wtlprnft's user avatar