33
votes
Accepted
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-...
- 213k
32
votes
Accepted
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 ...
- 4,643
30
votes
Accepted
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?
...
- 213k
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 ...
- 213k
28
votes
Accepted
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 ...
- 420
26
votes
Accepted
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 ...
- 16.7k
25
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
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24
votes
Accepted
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 ...
- 213k
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 ...
- 28.3k
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 ...
- 6,635
22
votes
Accepted
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.
- 1,043
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 ...
- 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". ...
- 10.2k
19
votes
Accepted
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 ...
- 213k
18
votes
Accepted
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 ...
- 1,012
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) - ...
- 1,547
16
votes
Accepted
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 ...
- 7,636
15
votes
Accepted
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 ...
- 213k
15
votes
Accepted
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 ...
- 8,549
15
votes
Accepted
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 ...
- 2,655
14
votes
Accepted
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 ...
- 213k
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 ...
- 261
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 ...
- 3,029
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 ...
- 2,317
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 ...
- 213k
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 ...
- 34.7k
11
votes
Accepted
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 ...
- 213k
11
votes
Accepted
Cost of dynamic versus static RAM in the early days
I did find some prices in BYTE:
November 1975, page 91
2107 4Kx1 Dynamic: $19.95 (0.49 cents/byte)
2111 256x4 Static: -- not listed
1101 256x1 Static: $2.25 (0.89 cents/byte)
April ...
- 1,101
11
votes
Which CPUs, if any, had an 8-bit address space?
The first that comes to mind is Cypress' M8C core used in the PSOC-1 series. While it has a 16 bit program address space (and thus 16 bit jump instructions), its data as well as the register space are ...
- 213k
11
votes
Accepted
How fast was Rambus compared to regular EDO RAM?
What's the question?
First problem here is what is to be considered speed.
Random access time?
Cycle time?
Maximum memory thruput?
Average memory thruput?
Either value per chip or
for the whole ...
- 213k
Only top scored, non community-wiki answers of a minimum length are eligible