Questions tagged [memory]

For questions about computer memory in a retrocomputing context

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25
votes
6answers
9k views

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 1Gb. Windows ...
10
votes
2answers
763 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 ...
8
votes
2answers
881 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 ...
27
votes
1answer
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)...
2
votes
0answers
107 views

Zip question for Amiga 3000T

I am trying to get a 3000T up and running, all seems good but there's no Fast RAM. All Zips ard populated. Is there any (easy) way to test the ZIPs? Also, could something like a bad cap kill the ...
10
votes
3answers
2k views

On a Gameboy, what happens when attempting to read/write external RAM while RAM is disabled?

According to the GBdevwiki: 0000-1FFF - RAM Enable (Write Only) Before external RAM can be read or written, it must be enabled by writing to this address space. It is recommended to disable ...
15
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3answers
1k 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 ...
38
votes
4answers
7k views

When did computers stop checking memory on boot?

I remember my old 8088 used to do this (640K OK) but can't remember seeing anything like this since. Does this still happen and it's just not visible? If not, when did it stop, and why? (Imagining ...
12
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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 ...
12
votes
1answer
325 views

How did restarts resolve parity errors triggered by broken core-rope wires?

In his account of the history of the Apollo Guidance Computer, Don Eyles describes the role of a parity bit as follows (p. 80): ... if one of those hair thin wires in our woven core-rope memory ...
15
votes
6answers
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 ...
4
votes
1answer
136 views

Was there any VIC-20 expansion to bring memory beyond the default maximum of 40 KiB?

The Commodore 64 was very flexible in terms of how RAM could be controlled. ROMs and I/O devices could easily be swapped out by setting bits in the first two addresses of memory. The VIC-20's ROMs and ...
25
votes
2answers
2k views

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 ...
9
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4answers
734 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. ...
18
votes
3answers
3k views

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 ...
1
vote
1answer
161 views

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?
5
votes
4answers
785 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 ...
17
votes
2answers
1k views

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 ...
17
votes
12answers
5k views

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?
9
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5answers
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, ...
9
votes
3answers
902 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 ...
1
vote
1answer
259 views

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. ...
8
votes
4answers
1k views

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 ...
7
votes
2answers
588 views

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 ...
13
votes
2answers
1k views

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 ...
20
votes
4answers
4k 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 ...
13
votes
2answers
432 views

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 ...
9
votes
1answer
402 views

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 ...
4
votes
4answers
309 views

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 ...
3
votes
1answer
202 views

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 ...
6
votes
1answer
156 views

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 ...
16
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3answers
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). ...
1
vote
1answer
266 views

'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 ...
8
votes
4answers
689 views

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 ...
5
votes
3answers
485 views

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 ...
13
votes
2answers
2k views

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....
11
votes
6answers
2k 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 ...
4
votes
1answer
208 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 ...
11
votes
3answers
800 views

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 ...
23
votes
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?
1
vote
1answer
356 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 ...
18
votes
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....
5
votes
2answers
258 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 ...
4
votes
1answer
256 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 ...
8
votes
1answer
572 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 ...
20
votes
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 ...
32
votes
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. ...
4
votes
3answers
436 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 ...
3
votes
2answers
267 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?
4
votes
4answers
512 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?