5 ms·
Ask HN: What numbers do you associate with old computers?
I'm writing a book on retro computers and the numbers that tie them together. (Full blurb and example prose at https://unbound.com/books/20goto10/)
What are the ultimately geeky, deep knowledge numbers, that aren't as obvious as 64K, 8, or 0's and 1's? (And bear in mind, I might need an explanation!)
Thanks in advance...
- PaulHoule 5y ago360, 3270
- stevengoodwin 5y agoCare to elaborate on their meaning, for the less informed?
- AnimalMuppet 5y ago360: IBM mainframe series. 3270: IBM terminal.
- brodouevencode 5y ago8008, 8086, 286, 386, 486 (Intel CPUs)
- eesmith 5y agoAnd of course other microprocessor part numbers, like the 6502 - https://en.wikipedia.org/wiki/MOS_Technology_6502 https://en.wikipedia.org/wiki/MOS_Technology_6502 .
- AnimalMuppet 5y ago36. It's the number of bits you need to represent 10 (decimal) digits fixed point, or 8 digits floating point. It's enough to calculate the differences of atomic masses. A number of early mainframes had 36 bit words for this reason. 80. The number of columns in a standard punch card. 132 (?). The number of columns in an extended punch card. 16407. On a TRS80 Model 1, the address of... something. Video controller register, maybe? Poking values into this register would result in weird (and sometimes entertaining) behavior on the screen. It often took a reboot to recover from, though.
- jonjacky 5y agoI've never seen any 'extended punch card', or any machine that could punch a 132-column card. 132 was the line length of IBM line printers, imitated by many other popular brands, including Printronix and DEC. They printed on that wide green-stripe, fan-fold paper, which came in a standard size that fit 132-column printers.
- eesmith 5y agoI agree about the (lack of) a 132 extended punch card. https://en.wikipedia.org/wiki/Punched_card#IBM_96-column_format https://en.wikipedia.org/wiki/Punched_card#IBM_96-column_for... points out there was a seldom used IBM 96 card. There's also Rand's 90 column card. I liked printing things out to the 132-column printer. I still don't stick to 80 columns in my code. ;)
- CharleFKane 5y agoRachel By the Bay posted a long list of "magic numbers" in November of last year, including some of significance for the C-64 and VIC-20. https://rachelbythebay.com/w/2020/11/26/magic/ https://rachelbythebay.com/w/2020/11/26/magic/
- pinewurst 5y ago28 is the I/O block size for Univac 1100s and their descendants, originating from FASTRAND horizontal drum devices.
- logotype 5y ago4000, 2000, 1200, 1000, 600, 500, 128, 64 - Commodore/Amiga
- philipswood 5y ago18.2 timer ticks per second on the old IBM PC timer interrupt.
- logotype 5y ago0x4489 - the MFM sync mark for Amiga Double Density (720k) floppy disks.
- jonjacky 5y ago12, the number of bits in the word of the PDP-8, the famous and influential minicomputer of the 1960s-70s. 4096, the number of words that can be addressed by 12 bits -- so, the size (in 12-bit words) of the PDP-8 memory. There was a whole culture of writing useful programs that fit in 4096 words -- not as a stunt or tour-de-force, that was just the order of the day.
- rachelbythebay 5y agoI see someone linked my post earlier (thanks!) but hey, I thought of a few more based on your request. 3583: BASIC bytes free on an unexpanded VIC-20. 38911: same idea for a C-64. Those were both prominent numbers since they showed up on the screen right when you turned it on and sat there until you got cranking on something else.
- eesmith 5y ago4.77MHz = frequency of the original IBM PC. 0xB8000 is the base address for the CGA video buffer on a 1980s era PC. 0xB0000 was for MDA (eg, a Hercules card). MDA's memory range didn't overlap with CGA, EGA, or VGA, so dual-head systems were possible, eg, program display on the color display, debugger in the monochrome display. My go-to book for the internals, with all sorts of numbers like the above, was "The Peter Norton Programmer's guide to the IBM PC", available at https://archive.org/details/peternortonprogr00nort https://archive.org/details/peternortonprogr00nort . For example, philipswood at https://news.ycombinator.com/item?id=28053235 https://news.ycombinator.com/item?id=28053235 pointed out the IBM PC timer interrupt was 18.2 ticks per second. Norton explains that at https://archive.org/details/peternortonprogr00nort/page/148/mode/2up?q=keyboard https://archive.org/details/peternortonprogr00nort/page/148/... - the main clock, the 8284A, oscillates at 1,193,180 times per second. The clock interrupt is every 65536 oscillations = 18.20648... ticks per second. And 1,193,180 * 4 = 4.77 MHz. Decimal 27 = hex 1B is a number I associate both with writing ANSI escape codes (still useful today), and with writing printer commands to my Epson MX-80, like setting to quad density mode for higher quality output. With 9-pins it could make very nice graphical printouts. 300, 1200, and 2400 baud were important modem speeds in my era. The earlier Bell 101 era used 110 baud.