Questions tagged [dram]
Dynamic Random Access Memory and its use in retrocomputers.
28
questions
12
votes
7
answers
5k
views
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 ...
- 63.1k
7
votes
2
answers
506
views
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 ...
- 27k
2
votes
0
answers
185
views
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 ...
- 121
6
votes
3
answers
1k
views
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 ...
- 63.1k
8
votes
1
answer
1k
views
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 ...
- 63.1k
11
votes
3
answers
846
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....
- 1,239
9
votes
1
answer
499
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 ...
- 63.1k
6
votes
1
answer
677
views
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 ...
- 61
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 ...
- 63.1k
6
votes
1
answer
877
views
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.
- 473
8
votes
1
answer
855
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 ...
- 263
0
votes
1
answer
234
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 ...
- 27k
4
votes
1
answer
288
views
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, $...
- 27k
4
votes
3
answers
642
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 ...
- 1,372
2
votes
2
answers
731
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 ...
- 63.1k