Questions tagged [memory]
For questions about computer memory in a retrocomputing context
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How does the Gameboy address external hardware?
Where in the memory map ($0000-$ffff) does the Gameboy address the memory of these accessories? (for example, the battery or the Gameboy Printer). Is this something I should implement in an emulator?
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How does the Gameboy's memory bank switching work?
I'm writing a Game Boy emulator, but I don't completely understand how its memory mapping works. Here is what I (think) I know (and don't know).
The CPU can address up to 0x10000 memory locations ...
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Details of video memory access arbitration in Space Invaders
I am working on an FPGA implementation of the original Space Invaders arcade machine and I'd like to implement access arbitration between the CPU and the video system. I can imagine several ways of ...
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Largest memory peripheral for Sinclair ZX81?
Back in the early to mid 1980s, I vaguely recall seeing an advert in a (I think) UK based computer periodical monthly (Your Computer, or Computer and Video Games), for a memory peripheral that offered ...
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How do I allocate more memory to an app on Sheepshaver running Mac OS 9?
I'm trying to play Taskmaker on Mac OS 9 in Sheepshaver on OSX. Taskmaker tells me that it doesn't have enough memory to run in color. Within technical support it says that I have 512 megabytes total ...
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What was the design of the Macintosh II's MMU replacement?
I am in the process of repairing a Macintosh II and trying to understand the design rationale behind Apple's MMU replacement part installed in this machine.
As you can see in the picture, there is a ...
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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 ...
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Protected/virtual memory support in classic AmigaOS
It is a well-known fact that AmigaOS is a single address space, totally unprotected memory operating system. The original implementation ran on a Motorola 68000, that did not support virtual memory if ...
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How much RAM did the first version of Oregon Trail on the Apple II require?
The later iterations of the series could have hundreds of kilobytes of RAM, but the original Apple II had 4K in the minimum configuration and 48K maximum (the latter using 16kbit chips which were ...
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Did the PC/AT-bus use its expanded address space?
The system bus of the IBM PC had 8 data lines and 20 address lines, in a logical correspondence to the 8088 CPU.
The AT added a second inline edge connector to expand this to 16 data lines and 24 ...
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Which Amiga systems did access RAM with fast page access?
I'm pretty sure Chip and Fast RAM access on an Amiga 1000 does not support FPM access.
Which Amiga system, chipset or motherboard "glue logic" first introduced FPM access to Fast RAM? Which one to ...
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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). ...
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How much time does a Mac SE/30 with 128 MB of memory take for its power-on memory test?
I've read that it should be possible to push the SE/30 to its maximum RAM capacity with eight pieces of 16 MByte, 30-Pin SIMMs. I've never seen such a machine in the wild. Neither with 64 or 80 MB. ...
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'Swap file' on early time sharing machines
In the Wikipedia article for time sharing, it says
The "state" of each user and their programs would have to be kept in the machine, and then switched between quickly. This would take up computer ...
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Why are RAM chips 1 or 4 bits wide?
I don't know whether it's still the case, but at least in the early days, it was common for RAM chips to be one bit wide, so e.g. an 8-bit computer would install them in groups of eight. I gather at ...
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Does fast page mode apply to ROM?
Starting with the 4116, RAM chips from the late seventies supported fast page mode, where if you were reading nearby – particularly, successive – words, you didn't need to supply both row and column ...
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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 ...
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IBM PC expansion card latency
In the IBM PC and early successors and compatibles, it was commonplace for most of the computer's memory to be on cards in general expansion slots. (e.g. the original IBM PC could take 64K on the ...
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Why does the Galaksija use SRAM instead of DRAM?
From what I understand, SRAM is more expensive than DRAM, but takes less support circuitry. That doesn't matter though, since the Z80 includes everything needed to refresh and support DRAM, doesn't it....
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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 ...
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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 ...
user11220
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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 ...
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Allocate 64 KiB in Watcom C 16-bit DOS
I'm trying to allocate a 64 KiB buffer in Watcom C 16-bit DOS. I'm using the "compact" memory model which defines the code segment to be limited to 64 KiB and addressed by near pointers (...
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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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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 ...
user6464
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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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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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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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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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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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Amiga 500+ rev8A, 1 MB chip RAM and 0.5 MB slow RAM
I have an 500+ rev8A, I added the missing 0.5 MB RAM and the U32 to the motherboard. I also have 512 KB in the trapdoor. This results in 1.5 MB chip RAM; but I want to have 1 MB chip RAM and 0.5 MB ...
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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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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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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, ...
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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. ...
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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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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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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 ...
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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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Testing RAM on an OmniBook 300?
I've got an old 386 laptop - specifically an OmniBook 300 - and I'm a little suspicious of the RAM. It's exhibited some very odd symptoms, such as memory-related crashes and boot failures, so I'd like ...
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Was photographic film ever used for digital 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 ...
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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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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 '...
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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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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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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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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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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 ...
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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 ...
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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 ...
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