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Questions tagged [dram]

Dynamic Random Access Memory and its use in retrocomputers.

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12 votes
7 answers
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Why didn't CPUs multiplex address pins like DRAM?

An important innovation for dynamic RAM was multiplexing address lines, so a 2^N-bit chip only needs N/2 address pins, which helps keep cost down. Why didn't CPUs match this? Setting aside e.g. the ...
rwallace's user avatar
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7 votes
2 answers
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How did DRAM refresh work on the Altair 4K dynamic memory boards?

The initial memory board shipped with the Altair 8800 was a 1K board using one to four pairs of Intel 8101 1024 bit (256 × 4) static RAM. Altair then started working on a 4K dynamic memory board. The ...
cjs's user avatar
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2 votes
0 answers
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Lower RAM module design for ZX Spectrum [closed]

While the upper DRAM chips for the ZX Spectrum (4164) are more stable and still accessable, the lower DRAM chips (4116) will become a critical component in the future. One of the solutions to this ...
Pygmalion's user avatar
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6 votes
3 answers
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Why doesn't the Acorn Electron use fast page mode?

The Acorn Electron, trying to provide 32K of RAM as cheaply as possible, uses four 64k chips, for a 4-bit data bus. Obviously, this involves trading away some performance. (In all the following ...
rwallace's user avatar
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8 votes
1 answer
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Did any 8-bit computers use 16kx4 RAM chips?

An 8-bit computer wanting 64K of RAM, could most straightforwardly use eight 64kx1 DRAM chips (64kbit, 1 data line). The Commodore 64 initially did this, but in the mid-80s, the cost-reduced redesign ...
rwallace's user avatar
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11 votes
3 answers
837 views

TMS9918 - why have separate data-in and data-out?

Usually 8bit video chips interface with DRAM using: an address bus for rows and columns, a bidirectional data bus in the case of 1bit DRAM data-in and data-out pins are shorted on the same data line....
Valentino Miazzo's user avatar
9 votes
1 answer
486 views

Did the Vic-20 save money using static RAM?

The unexpanded Vic-20 had 5K of RAM. This was quite small even by 1981 standards, but it was trying to be cheap enough for consumers to buy, and it succeeded, selling over 2 million units. One reason ...
rwallace's user avatar
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6 votes
1 answer
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How does POST memory test work on a relatively modern (2000s) PC? Does it still test every single byte like on older ones?

I have an Asus eee 4G (AMI BIOS), I want to ask if this product actually overwrites the entire RAM during cold boot. I have the "Quick boot" feature turned off and I can see the memory being ...
Hasbo's user avatar
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16 votes
1 answer
3k views

Was any DRAM ever slower than 2 MHz?

4096-bit dynamic RAM chips were commonly used for main memory in microcomputers of the late seventies. According to the Mostek MK4096 datasheet, it was sold in various speed grades, with the slowest ...
rwallace's user avatar
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6 votes
1 answer
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Why were ZIP DRAM packages ever considered if PLCC/SOJ sockets were available?

Even in the 1980s, PLCC sockets were available, and PLCC/SOJ was already being used in SIMMs.
Yuhong Bao's user avatar
8 votes
1 answer
815 views

How does the VIC-II/CPU memory access work on the C64?

As a programmer I knew that on the C64 the CPU got the bus in the high phase of PHI2 and the VIC-II got it in the low phase and also stole extra high phases when required. However, it wasn't until ...
Robin Elvin's user avatar
0 votes
1 answer
229 views

How are Apple II address lines mapped to DRAM rows and columns?

The Apple II's MK4096 (4 Kbit) and MK4116 (16 Kbit) DRAM chips have 6 and 7 (respectively) address line inputs that are multiplexed: first the row address bits and then the column address bits are ...
cjs's user avatar
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4 votes
1 answer
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Does the Apple II's non-linear frame buffer layout help DRAM refresh?

The Apple II uses non-linear frame buffers for text and graphics. Rather than storing each line in sequence at lines 0-23: $400, $428, $450, $480,¹ ..., $7D0 it stores them at lines 0- 7: $400, $...
cjs's user avatar
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4 votes
3 answers
635 views

Were there low-end eighties computers that used dual-ported video RAM?

Going through schematics of several home or small office computers of the era, I was wondering why almost none of them (1) used dual-ported video RAM. I understand that those chips were initaly ...
airman's user avatar
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2 votes
2 answers
709 views

What was the DRAM refresh interval on early microcomputers?

Dynamic RAM is denser than static RAM, but needs to be refreshed every few milliseconds to avoid losing data. How many milliseconds, exactly? If the answer has changed over time, then I'm interested ...
rwallace's user avatar
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16 votes
2 answers
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What process node were 4k and 16k DRAMs first made at?

In the history of computers, much is said of microprocessors, for good reason, but the relatively unsung RAM chips were equally important. Of particular significance were the 4kbit and 16kbit dynamic ...
rwallace's user avatar
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2 votes
1 answer
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TMS9918ANL question

I am working on setting up a TMS9918ANL Video Display Processor. I was wondering if there is any way I can test to see if it is working without having the DRAM hooked up (I have a while before the ...
benjamin black's user avatar
6 votes
3 answers
757 views

How does DRAM refresh work in the Leningrad?

The Leningrad uses the КР565РУ5 chip, which is the same as a 4164. It contains 64kbits of DRAM, and the datasheet says that each of the 256 row addressed need to be strobed every 4ms. I can see how ...
Omar and Lorraine's user avatar
32 votes
3 answers
6k views

What is DRAM refresh and why is the weird Apple II video memory layout affected by it?

I've roughly known the concept for years, but never really understood it. Back in the day, two types of RAM typically used in home computers: static and dynamic RAM. Static RAM (SRAM) was apparently ...
bjb's user avatar
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10 votes
2 answers
867 views

How fast did the ARM-1 access memory?

The ARM-1, an early 32-bit RISC CPU, was used in the Acorn Archimedes computers, released in 1987. Its rated speed was one 32-bit instruction per cycle at 8 MHz. Typical RAM chips at that time would ...
rwallace's user avatar
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2 votes
1 answer
372 views

What were the wholesale costs of 256kbit vs 1Mbit DRAM chips in 1994?

In the early eighties, 64kbit DRAM chips replaced 16kbit ones by being cheaper per bit. Around 1987, 256kbit replaced 64kbit in turn, so computers like the Commodore 64 started using two of them for ...
rwallace's user avatar
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10 votes
1 answer
1k views

What sort of RAM chips did the Commodore 64 use in 1994?

For the first few years after its release in 1982, the Commodore 64 used eight RAM chips of 64kbit each. In the late eighties, it became cheaper to use a pair of 256kbit chips of the 4-bit-wide ...
rwallace's user avatar
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10 votes
3 answers
1k 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 ...
rwallace's user avatar
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10 votes
1 answer
1k views

How did the ZX80 RAM pack use DRAM?

The Sinclair ZX80 was the most popular personal computer in Britain at the beginning of the 1980s, due to its low price which was enabled by extreme minimalism; it consisted of not much more than a ...
rwallace's user avatar
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4 votes
1 answer
291 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 ...
rwallace's user avatar
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10 votes
3 answers
974 views

Why do Early DRAMs (e.g. 4116) have a negative Column Address Set-up Time?

Early DRAMs have a multiplexed address bus. Briefly speaking, to access a word, one needs to... Put the row address on the bus, and latch it using the falling edge of /RAS signal. Put the column ...
比尔盖子's user avatar
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35 votes
6 answers
10k views

Using DRAM as a camera sensor?

Back in the days when COMECON (RVHP) was cloning digital ICs usually the first wave of such ICs were in a ceramic package with a glass window (similar to EPROM) to check for bugs and stuff while used. ...
Spektre's user avatar
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13 votes
3 answers
2k 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 ...
rwallace's user avatar
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