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Questions tagged [memory]

For questions about computer memory in a retrocomputing context

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9
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3answers
722 views

Cost of dynamic versus static RAM in the early days

Early pioneers building memory cards for personal computers, tended to use static RAM, because it's quite a bit easier to get to work. Later, dynamic RAM became de rigueur, for the simple and ...
8
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3answers
2k views

Did multiplexed address/data lines make memory access slower?

Looking at the pinout of e.g. the 8088, it multiplexes the data lines onto eight of the address lines; presumably the designers judged that being able to squeeze the chip into a 40-pin package, would ...
-1
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1answer
350 views

Get himem.sys working on a p7xxDMx outside the VM

I tried many 98SE boot disks online, they all boot successfully on my mobile workstation from USB (C:\>), but all can't run the Windows 98SE Installer because of XMS Memory, giving an error like: ...
2
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1answer
91 views

How long would a 41256 take to do 4 accesses in fast page mode?

I have been surprised at how little use eighties computers made of fast page mode access to RAM. (A notable exception being the Sinclair Spectrum, which used it to get the necessary bandwidth to video ...
1
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4answers
115 views

Will any modern EEPROM programmer work with the IP3604/КР556РТ5?

Just to say I'm completely new to the world of PROM and I'm a bit bewildered. My ultimate aim is to be able to program these Russian 4k bipolar PROM chips, which are the equivalent of Epson IP3604, ...
8
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2answers
230 views

When was the first 3 state IC produced?

This was prompted by a question on the electronics site (which was asking why only an open collector variant of a particularly old part existed and how it could be part of a data bus). This was a ...
1
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3answers
305 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 before 1984 . Without needing to plug in any ...
23
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1answer
2k views

What is a dropfile?

After reading Charles Duffy's comment on Was there a clearly identifiable "first computer" to use or demonstrate the use of virtual memory?: I had a computer science professor around 1999 ...
8
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1answer
208 views

What's the difference between the DOS HIMEM.SYS and the Windows 3.x version?

An installation of DOS (e.g. MS-DOS 5.0) will typically include a statement in its CONFIG.SYS such as DEVICE=C:\DOS\HIMEM.SYS. When installing Windows 3.1, it's setup comments (REMs) that line out, ...
12
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1answer
1k views

What manages Upper Memory Blocks (UMBs) in MS-DOS?

I had always assumed that EMM386.EXE was responsible for managing the Upper Memory Blocks - UMBs - the memory space between 640KiB and 1MiB in real mode x86. For example, on MS-DOS 6.22, help emm386....
6
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2answers
296 views

what is DMA and how does it work?

I've heard the term 'DMA' being used a lot in reference to older consoles. My very basic understanding is that it's a way for the console to access memory directly. But directly as apposed to what? ...
4
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1answer
476 views

How did “RAM” cartridges for the C64 work?

Section 7.1.1.2 of the VICE manual mentions that cartridge slot 1 (of the four slots 0, 1, Main and I/O) in the emulator is special in that it's designed to support "mostly RAM-based cartridges" (of ...
6
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1answer
221 views

Why does my Amgia 3000 show no Fast RAM even though the ZIP sockets are populated?

I am trying to get an Amiga 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 ...
15
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1answer
524 views

Under what circumstances would RAM locations 0 and 1 be written and/or read on the C64?

To be clear, I'm talking about the actual memory cells at addresses $0000 and $0001 in the DRAM chips. Devices can of course initiate read or write requests to these address on the address/data buses ...
39
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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 ...
28
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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)...
12
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1answer
337 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 ...
4
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1answer
150 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 ...
10
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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 ...
1
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1answer
182 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?
19
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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 ...
25
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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 ...
8
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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
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2answers
649 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
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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
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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
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2answers
491 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 ...
3
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1answer
222 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 ...
5
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5answers
388 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 ...
7
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1answer
206 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
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1answer
269 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. ...
1
vote
1answer
271 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 ...
5
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3answers
610 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 ...
8
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4answers
700 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 ...
4
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1answer
218 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
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3answers
829 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 ...
13
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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....
2
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1answer
396 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 ...
4
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1answer
268 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 ...
5
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2answers
260 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
599 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 ...
19
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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 ...
32
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7answers
10k 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. ...
5
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4answers
952 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 ...
19
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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....
13
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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 ...
4
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2answers
301 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?
10
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1answer
458 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 ...
2
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1answer
221 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 ...