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Questions tagged [ram]

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6
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2answers
291 views

Is it safe for C64 cartridges to respond to read and/or write requests on “unmapped” addresses?

According to the C64 wiki, asserting G̅A̅M̅E̅ on the cartridge port (and not asserting E̅X̅R̅O̅M̅) of the C64 leaves three blocks of the C64 address space "unmapped": 28 KB @ $1000 (otherwise RAM), 8 ...
10
votes
2answers
1k views

Small RAM 4 KB on the early Apple II?

Most of the reference material for the Apple II that I have seen refers to the 4116 RAM chip which held 16x1 kbit. This provided 16, 32 or 48 KB in banks of 8 chips. The Apple II motherboard layout ...
13
votes
2answers
575 views

Atari ST DRAM timing puzzle

From the Atari SM124 Monochrome Monitor Service Manual, I get that the video signal timing for one line is 20µs. With the horizontal resolution of 640 pixels, this gives a 31.25ns pixel clock. Using ...
11
votes
1answer
2k views

3 beeps on a 486 computer with an American Megatrends bios?

So far I've figured out that means something about the ram bit I haven't been able to figure out what the problem is Edit: video link
4
votes
1answer
137 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 ...
6
votes
1answer
244 views

The IBM RAM with non-standard pin layout

One and half decade ago I had an black IBM Thinkcentre tower. The specs were: Pentium 4 2.66 GHz 256 Mb IBM RAM (which later got upgraded into 512 Mb RAM), 40GB HDD, XP Pro SP3, GeForce 2 MX 400. ...
1
vote
2answers
240 views

Parity error under DOS

I'm facing a Parity Error problem on my new 486er DOS Retro PC. Every now and then a running software crashes with a Parity Error output on screen. This happens for different software so I think the ...
9
votes
1answer
168 views

Patch BBC Master ROM using Sideways RAM?

I have a BBC Master 128 with the standard ROM installed. This includes ADFS v1.50 in slot "D". I want to replace this ADFS in ROM with a patched version, loaded from disk, into Sideways RAM. It is a ...
5
votes
3answers
488 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 ...
12
votes
2answers
680 views

Why was BASIC on the Commodore 64 one byte shy of 38KiB?

When you power up a Commodore 64 you are greeted with a friendly message telling the user it has 38911 BASIC bytes free. 38,911 is one byte shy of a 38 KiB (1,024 * 38 = 38,912). What was the reason ...
1
vote
1answer
171 views

Does the TurboGrafX16 store switches and/or flags in RAM?

Based the the specs I found for the TG16, it has 8 KB of RAM. I also found notes in the documentation of many opcodes that there is data stored in several "flags and switches" are these stored in RAM ...
20
votes
2answers
2k views

Why does the VIC-20 have 5KiB of RAM?

Why does the VIC-20 have 5 KiB of RAM? Why not a multiple of 4 as any other systems, e.g 4 KiB or 8 KiB. Is there a technical reason for that?