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Questions tagged [memory]

For questions about computer memory in a retrocomputing context

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11 votes
3 answers
2k views

What are the minimum system requirements to run GW-BASIC?

In DOSBox 0.74, I can run GWBASIC.EXE without any problem (DOSBox reports 632 KB of free conventional memory). It is GW-BASIC's version 3.10 dated 01-07-1989 with filesize 72576 bytes. On screen it ...
26 votes
3 answers
5k views

Why do old computers (PCs) 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....
13 votes
6 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 ...
10 votes
5 answers
6k views

When did the PC bus start slowing access to video RAM?

The PC architecture, from the original IBM PC onward, has always been designed around the idea that video memory will be on an expansion card. This was an unusual design decision; most 80s computers ...
25 votes
5 answers
7k views

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 ...
9 votes
10 answers
1k views

Were there any games/software that used memory beyond what was advertised available to BASIC on the machine?

Were there any games/software that used memory beyond what was advertised as available to BASIC on the machine ? On home / personal computers any time up to 1984 . Without needing to plug in any ...
20 votes
2 answers
2k views

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 ...
8 votes
4 answers
662 views

VAX 11/780 16MB memory board - what was the physical size?

I'm trying to get a feel for what it looked like when you designed a computer to have a lot of memory chips stuffed into it. To that end, I found this: https://commons.wikimedia.org/wiki/File:...
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 — ...
3 votes
2 answers
313 views

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 ...
15 votes
4 answers
3k views

Is this the reason why fread/fwrite has 2 `size_t` arguments?

It just came to me that, the C standard I/O functions fread and fwrite are having 2 size_t arguments because of I guess possibly, that on some systems, there may be more memory of which whose size can ...
23 votes
3 answers
5k views

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 ...
8 votes
5 answers
2k views

Largest memory peripheral for Sinclair ZX81?

Back in the early to mid 1980s, 1981-1983, I vaguely recall seeing an advert in a (I think) UK based computer periodical monthly (such as Your Computer, or Computer and Video Games), for a memory ...
30 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)...
32 votes
1 answer
3k views

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)...
8 votes
1 answer
1k 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 ...
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 ...
10 votes
1 answer
1k views

How much memory did the PlayStation development kit have?

The PlayStation 1 had two megabytes of main memory, one megabyte of video memory and half a megabyte of audio memory. Squeezing everything to fit into these limits was one of the big challenges of ...
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 ...
8 votes
2 answers
678 views

Could the Apple IIGS play any and all Amiga MOD files?

The Apple IIGS has a wavetable synthesis sound chip with dedicated 64 kilobytes of RAM. I assume the sound architecture dictates that samples have to be loaded into that dedicated RAM to be able to be ...
19 votes
4 answers
4k views

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). ...
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 ...
13 votes
2 answers
996 views

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-...
9 votes
1 answer
477 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 ...
13 votes
3 answers
2k views

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 ...
9 votes
2 answers
1k views

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 ...
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?
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 ...
4 votes
4 answers
810 views

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 ...
7 votes
1 answer
369 views

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, ...
10 votes
4 answers
3k 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 ...
13 votes
3 answers
2k 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 ...
8 votes
1 answer
505 views

Why does my Epson HX-20 apparently have much less RAM than expected?

When I enter: STAT ALL On my Epson HX-20, I get the following output: P1: 419 Bytes P2: 86 Bytes P3: 0 Bytes P4: 0 Bytes P5: 0 Bytes RAM FILE 256 Bytes MEMSET 2624 105 Bytes Free As I ...
23 votes
11 answers
5k views

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 ...
10 votes
2 answers
706 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 ...
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?
6 votes
1 answer
655 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 ...
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 ...
3 votes
0 answers
286 views

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 ...
13 votes
2 answers
747 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 ...
6 votes
3 answers
1k views

Does the 8080 always handle unaligned access correctly?

The 8080 is referred to as an 8-bit CPU because it has an 8-bit data bus, but there are a number of cases where it must perform 16-bit memory access, for example when reading or writing a 16-bit ...
11 votes
3 answers
749 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 ...
30 votes
7 answers
18k 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 '...
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&...
3 votes
0 answers
287 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 ...
1 vote
2 answers
607 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 ...
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 ...
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 ...
17 votes
9 answers
4k 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 ...
5 votes
2 answers
532 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 ...