Skip to main content
Share Your Experience: Take the 2024 Developer Survey
48 votes

Why didn't Microsoft use a well-known encryption algorithm like RSA for telephone activation?

My question is why didn't Microsoft simply use RSA or another proven algorithm? Because they thought it was important to minimize the signature. That is, in the use case: For those who don't know I ...
poncho's user avatar
  • 581
33 votes
Accepted

Why does the Commodore 64 have 4K of non-banked RAM at $C000?

I wonder why the Commodore 64 memory map was created as it was. As so often it helps to look at a machine's predecessor; in the case of the C64 that's not the VIC 20, but the Max Machine, a very ...
Raffzahn's user avatar
  • 224k
29 votes
Accepted

Was there any computer since about 1960 without interrupt support?

The Wang 2200 series of minicomputers (Apr 1973 to Jul 1989) was implemented without hardware interrupts. All peripheral interaction was handled via polling. These machines were fitted with a BASIC ...
A. I. Breveleri's user avatar
26 votes
Accepted

Why does PC video memory base address change depending on video mode?

The history behind the various base addresses is as follows: the area starting at A0000h was set aside for video frame buffers in general (see Who set the 640K limit?) MDA used 4KiB starting at ...
Stephen Kitt's user avatar
23 votes

Was there any computer since about 1960 without interrupt support?

The first microprocessor, the Intel 4004, had no interrupt capability. Its successor, the 8008, had interrupts, but with the shallow call stack and the need to reserve scarce registers to do any sort ...
John Doty's user avatar
  • 2,779
21 votes

Was there any computer since about 1960 without interrupt support?

Sharp pocket computers based on the ESR-H SC61860 micro-controller (PC-12xx, 13xx and 14xx) did not have interrupts. No instructions like rti, nothing. Everything was done by polling (it had for ...
Patrick Schlüter's user avatar
19 votes

Was there any computer since about 1960 without interrupt support?

Would embedded systems count? If yes, there were GI's PIC1600 MCUs (http://bitsavers.org/components/gi/PIC/1983_PIC_Series_Microcomputer_Data_Manual.pdf), predecessors of PIC microcontrollers by ...
lvd's user avatar
  • 10.5k
17 votes

Why didn't Microsoft use a well-known encryption algorithm like RSA for telephone activation?

Opinion: RSA received a patent for the algorithm in 1977. Microsoft was unlikely to use someone else's patented algorithm. Though the RSA patent became public-domain in September 2000, and Windows XP ...
dave's user avatar
  • 35.7k
14 votes

Why does PC video memory base address change depending on video mode?

TL;DR: Compatibility Before VGA there was MDA, CGA and EGA and it's all about continued support. But Why Different Memory Regions ? Video in the IBM PC is based on video cards bringing their own ...
Raffzahn's user avatar
  • 224k
14 votes

Why didn't Microsoft use a well-known encryption algorithm like RSA for telephone activation?

After 20 years You could argue that the encryption was plenty strong enough. Support for XP ended nearly 15 years ago, the encryption lasted 15 years longer than the OS. All security systems have to ...
Alan Birtles's user avatar
12 votes

Was there any computer since about 1960 without interrupt support?

Lots of examples could be found among many of USSR era home computers based on the KR580VM80 chip (a clone of i8080). In a normal i8080 system, the CPU is supposed to work with companion (or 'chipset')...
lvd's user avatar
  • 10.5k
11 votes
Accepted

In the RL02 disk system, why does the “read” command take CHS coordinates, when there is also a separate “seek” command?

The "normal" read and write commands will wait until it sees the header for the appropriate sector and then read or write the following data record. If the head isn't already in the right ...
supercat's user avatar
  • 36.5k
11 votes

Was there any computer since about 1960 without interrupt support?

Although the Apple II family of computers allows I/O cards to use interrupts, none of the internal hardware on the Apple II nor the Apple //e offers any support for them beyond making the pins ...
supercat's user avatar
  • 36.5k
10 votes

Was there any computer since about 1960 without interrupt support?

Another example from the embedded world: the Parallax Propeller uses multiple CPU cores to service events instead of interrupts. https://en.wikipedia.org/wiki/Parallax_Propeller#...
filo's user avatar
  • 391
8 votes

Why does the VIC-20 have its cartridge area at a higher adress than the I/O area?

Why did the designers of the Commodore VIC-20 chose to put the main cartridge ROM area at $A000, beyond the character ROM area at $8000 and the I/O area at $9000? Because that's the natural order for ...
Raffzahn's user avatar
  • 224k
8 votes

Was there any computer since about 1960 without interrupt support?

The Atari 2600 Video Computer System draws its entire screen using techniques that on other systems would be accomplished via raster interrupts, but its 6502 die is in a 28-pin package that omits both ...
supercat's user avatar
  • 36.5k
7 votes

What prompted Nintendo to use SRAM rather than DRAM for the PPU memory on the Famicom?

The PPU used in the NES/Famicom is designed with a 16K address space, which was expected to be filled with an 8K ROM chip on a cartridge and a SRAM That's not what the NES wiki states: $0000-1FFF is ...
dirkt's user avatar
  • 27.8k
6 votes

What prompted Nintendo to use SRAM rather than DRAM for the PPU memory on the Famicom?

Was the cost of a 2Kx8 RAM, plus an address latch, plus all the cartridge pins needed to expose the video bus, less than the cost of eight 16Kx1 or two 16Kx4 DRAM chips? The DRAM would have been ...
qwerty keyboard's user avatar
6 votes

Why does PC video memory base address change depending on video mode?

For CGA vs. MDA, the reasoning for using different base adresses is simple and obvious: These two video systems are designed to co-exist for dual-monitor solutions thus each need a unique memory range....
tofro's user avatar
  • 35k
6 votes

Was there any computer since about 1960 without interrupt support?

The Parallax Propeller processor for quadcopters has (I write has because it's in production today for its intended purpose) no interrupts, and this is an advertised feature (so that execution ...
Joshua's user avatar
  • 1,839
6 votes

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

Let's see the datasheet for 9918 first and see how the VDP to VRAM write sequence works. Before the write cycle, the VRAM chips were all held in the READ mode (R/~W signal is held high by VDP). This ...
user3528438's user avatar
  • 1,395
5 votes
Accepted

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

The TMS9918 has eight pins that combine "address out" and "data out" functions, while using another eight pins for "data in". Because typical 16Kx1 DRAM chips don't have ...
supercat's user avatar
  • 36.5k
4 votes

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

TL;DR: It's two chips in one A memory manager/addressing unit and a streaming display engine (*1), each with their own dedicated data port. Splitting the structure into two unidirectional interfaces ...
Raffzahn's user avatar
  • 224k
3 votes

What prompted Nintendo to use SRAM rather than DRAM for the PPU memory on the Famicom?

The TMS9918 derivative which was used in the NES/Famicom (the Ricoh 2C02) simply didn't have the RAS/CAS pins to use DRAM. Note that the TMS9918 and the Ricoh 2C02 are not pin-compatible! The 2C02 had ...
Klaws's user avatar
  • 521
2 votes

Why does the x86 not have an instruction to obtain its instruction pointer?

8086 uses a segmented memory model with the address instructions are fetched from calculated by CS * 16 + IP. For position independent code one would fix IP at link time and choose CS at runtime. It ...
Timothy Baldwin's user avatar
2 votes

When and why was the question mark chosen to abbreviate PRINT?

I checked some HP TSB manuals from 1969 to 1976 and found no mention of "?" for PRINT. HP TSB was my first experience with programming BASIC and I never used "?" for PRINT back ...
Peter McGavin's user avatar
2 votes

Was there any computer since about 1960 without interrupt support?

Yeah, the higher perfromance CP/M computers (either an 8080 or Z80 processor) had interrupts but some had to poll the devices. These used a BIOS so your CP/M applications could access the screen, disk(...
hwertz's user avatar
  • 219
1 vote

What prompted Nintendo to use SRAM rather than DRAM for the PPU memory on the Famicom?

DRAM would have needed refresh circuitry and address multiplexing. And as Nintendo needed an 8-bit bus and DRAMs of the time were 1-bit parts they would have needed 8 parts instead of 1 with costs in ...
Exophase's user avatar
  • 111

Only top scored, non community-wiki answers of a minimum length are eligible