56 votes

How did the Atari 2600 achieve a resolution of 160 x 192 pixels with only 128 bytes of memory?

The 2600 didn’t have a frame buffer. Instead, programs running on it had to draw the picture on the screen pretty much in real time. This actually had some advantages on a low-cost system. Each line ...
Stephen Kitt's user avatar
37 votes
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How did the Atari 2600 achieve a resolution of 160 x 192 pixels with only 128 bytes of memory?

According to wikipedia, the Atari 2600 had a resolution of 160 x 192 pixels. had it been monochrome, it would had needed 160*192 = 30,720 bits of video RAM, or 3,840 bytes. Even more taking colour ...
Raffzahn's user avatar
  • 223k
33 votes
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What kind of RAM stick is this?

Despite the 144 pin DIMM form factor, this is not a SDRAM, but an EDO module with 16 MiB capacity. The used RAM chips are KM48C2104 (KM48 marks RAMs) Manufactured by Samsung, of 16 MiBit Capacity EDO-...
Raffzahn's user avatar
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32 votes
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Release timeline for 128KB personal computers?

The Apple III came with a minimum of 128K of RAM (expandable to 512K) two years before Commodore had a series of CBM-II computers with 128K minimum and expandable to 896K in 1982 a year before the IBM ...
Tim Locke's user avatar
  • 4,811
30 votes
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Why does the VIC-20 have 5KiB of RAM?

Simple reason: Commodore had an overstock of 2114 Chips at that time (*1), so Jack Tramiel, then president of Commodore, ordered the project (*2) to use them. Yeah, but why 5 KiB? Why not just 4KiB? ...
Raffzahn's user avatar
  • 223k
29 votes
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What is a "sympathetic bit"?

What is a "sympathetic bit", and why must IBM PCs check for it? Sympathic Bits, in this context, are bits within a data word that always flip with some other bit. For example when a word ...
Raffzahn's user avatar
  • 223k
28 votes
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Which CPUs, if any, had an 8-bit address space?

PIC: 7 bit address space The Microchip PIC family of CPUs specifically the 10, 12 and 16 series have 7 bits of address space. While 7 bits is not exactly 8 bits this shows that there are commercial ...
slebetman's user avatar
  • 420
27 votes

Which CPUs, if any, had an 8-bit address space?

The KENBAK-1 has 256 bytes of memory. I'm not certain whether it had an 8-bit PC. https://en.wikipedia.org/wiki/Kenbak-1
Tim Locke's user avatar
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26 votes
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3 beeps on a 486 computer with an American Megatrends bios?

Here is a reference to BIOS beep codes. For American Megatrends, look under AMI. 3 beeps means the low 64K failed - a very basic test - which probably means the RAM isn't working at all. You ...
Chromatix's user avatar
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24 votes
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Why was BASIC on the Commodore 64 one byte shy of 38KiB?

Well, it's a 'trick' to simplify the editor as well as the BASIC editor. After Reset (or NEW) three bytes of Zero are placed at the beginning of the basic RAM. They make it look to the basic ...
Raffzahn's user avatar
  • 223k
22 votes

Why did old consoles have special RAM dedicated for a specific task?

It's not limited to just consoles. Average PC in similar era than PS1 made the same distinction with several specialized memory areas for same reason. For example in a PC the CPU has memory it can use ...
Justme's user avatar
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22 votes

Why did old consoles have special RAM dedicated for a specific task?

The most peculiar example of RAM dedicated to a single task was the Spanish version of the Amstrad CPC464, the CPC 472. This machine an extra 64kx1 DRAM chip which was not connected to anything. Its ...
Bruce Abbott's user avatar
  • 6,673
22 votes
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Was any DRAM ever slower than 2 MHz?

From the 1975 Intel Data Catalog entry for the 1103: one sees that a write or read/write cycle is specified as a minimum of 580 nsec. This corresponds to a speed of 1.724 MHz.
Jon Custer's user avatar
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21 votes

Is it possible to raise the frequency of command input to the processor in this way?

You can take two identical RAM chips and run them by changing the frequency in the clock signal in one of chip. Pick up such a shift that. The 1st chip is being recharged, the 2nd chip is giving a ...
Wayne Conrad's user avatar
  • 2,706
19 votes

Why did 1-bit DRAM chips have separate data input and output?

Because there were spare pins otherwise. Because sometimes this could make the design simpler. As an example, I'll put again schematics of a russian ZX clone, for example this one, named "Leningrad". ...
lvd's user avatar
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19 votes
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When did half-bad RAM chips stop being available?

Sinclair's use was a very unique case in a very specific situation that never occurred again later on. Production side: There were many more manufacturers of chips back then. The ones that wanted to ...
Raffzahn's user avatar
  • 223k
18 votes
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How can I resolve these intermittent memory issues?

After removing some more components, and getting under the floppy drive with some light for inspection, I found three "Chhsi"-branded capacitors that were bulging. These caps are part of the ...
Brian Reading's user avatar
17 votes

Release timeline for 128KB personal computers?

Soviet: ES PEVM (IBM PC clone) - 1986 Okean-240 (128 KB, Intel 8080 class) - 1986 UKNC (192 KB, PDP-11 class) - 1987 DVK-3M (248 KB, PDP-11 class) - 1987 Korvet (112-256 KB, Intel 8080 class) - ...
Anixx's user avatar
  • 1,547
17 votes

How did the Atari 2600 achieve a resolution of 160 x 192 pixels with only 128 bytes of memory?

The Atari VCS (it only became the Atari 2600, when the 5200 became a thing) is somewhat peculiar, as its video and audio chip, the "Television Interface Adapter", better known as TIA, ...
masswerk's user avatar
  • 406
16 votes
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Is solder-on memory upgrade an option here and how to check it

The daughterboard is the graphics card. The GD610/GD620 is a quite common chipset for LCD/VGA graphics in laptops. It uses two 64k x 16Bit RAM chips to obtain 64k x 32Bit, which is the usual VGA ...
Michael Karcher's user avatar
15 votes
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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. Jup, at the time the Apple II really took off, 4116 chips had already dropped to ...
Raffzahn's user avatar
  • 223k
15 votes
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What process node were 4k and 16k DRAMs first made at?

Intel manufactured its 1-kilobit 1103 RAM on an 8 μm P-MOS process. Through most of the 1970s, DRAM was made from NMOS. The first successful CMOS memory was the Hitachi HM6147 SRAM, a 4-kilobit chip ...
Davislor's user avatar
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15 votes
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Is there an util that maps part of HDD to upper memory to create UMBs?

Probably not much else you can do with that RAM. You say the RAM “is” a RAM drive. It’s far more likely that there is extra RAM on the motherboard and that there is a RAM Drive driver installed that ...
Euro Micelli's user avatar
  • 2,685
14 votes
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Atari ST DRAM timing puzzle

How two 260ns RAM accesses could fit in 500ns? By using a 250ns (*1) tRC cycle? And yes, strictly that's out of spec. Still chances are very good that each and every chips will make it, as the timing ...
Raffzahn's user avatar
  • 223k
14 votes

Amiga A1050 schematic

Finally designed and built an Amiga A1050 knockoff. Seems to work well on my Amiga 1000. Schematic, PCB and BOM is posted on github https://github.com/TheOrangeStrain/Amiga-A1050-RAM-Expansion The ...
TheOrangeDude's user avatar
13 votes

Decoding Logic and Memory Systems for 8-bit computer - 64K address space

Your observation about the 64K address space is correct, your 32K RAM and 32K EEPROM will be able to fill that address space to 100%. In Z80 designs, the ROM/PROM/EPROM/EEPROM is usually placed ...
jwh20's user avatar
  • 3,049
13 votes

Back in the day, were games coded to run better with more (not faster) RAM?

The year you've picked has a strong influence on the answer. By 1999, most new games were being released to run under 32-bit Windows using DirectX, and were therefore running in a demand-paged ...
occipita's user avatar
  • 2,357
13 votes

Is it possible to raise the frequency of command input to the processor in this way?

In the 70's and 80's RAM chips worked at a lower frequency than the CPU. That is, the processor worked at a frequency higher than the RAM. Not really. At least with microprocessors, RAM was usually ...
Raffzahn's user avatar
  • 223k
12 votes

What is a "sympathetic bit"?

If an address signal on a RAM chip or board is not connected properly, any attempt to write to either of the addresses distinguished by that bit will behave as though it writes to both of them. This ...
supercat's user avatar
  • 36.3k
11 votes
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Commodore Plus/4 60671 bytes free - how?

[...] Commodore 64 did indeed provide 64K of RAM [...] only 38K was usable from BASIC; [...] bank switching was needed to get at the rest, And that's exactly the way the TED computers did use. but ...
Raffzahn's user avatar
  • 223k

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