Imran Nazar ~ عمران نزر
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imrannazar.com
Imran Nazar ~ عمران نزر
@imrannazar.com
150 followers 1.5K following 300 posts
Front-end #typescript developer, author of RFC 7168 (HTCPCP for teapots); occasional plumber, more than occasional #c64 #retrocomputing enthusiast, terrible at #piano.

Header photo is a verdant scene looking over the landscape near Buxton, England.
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imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 20: Isaac Asimov/Robert Silverberg, Nightfall

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Asimov and Silverberg's Nightfall. Photo credit: pinterest/Randy Marcy
December 30, 2024 at 2:22 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 19: Andy Weir, The Martian

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Weir's The Martian, depicting an astronaut peering into the distance with a hand above their visor. Photo credit: Victoria Reads
December 29, 2024 at 1:56 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 18: Greg Egan, Permutation City

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Greg Egan's Permutation City, depicting a wordsearch with permutations of the phrase "Permutation City". Photo credit: goodreads
December 28, 2024 at 1:28 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 17: Bruce Sterling, The Hacker Crackdown

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Bruce Sterling's Hacker Crackdown, subtitled: Law and disorder on the electronic frontier. Photo credit: Another one that's mine
December 27, 2024 at 1:21 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 16: Isaac Asimov, In the Beginning: Science Faces God in the Book of Genesis

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Hardcover small-format edition of Asimov's In The Beginning, subtitled: Science Faces God in the Book of Genesis. Photo credit: Another one that's mine
December 25, 2024 at 4:41 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 15: Arthur C Clarke, Rendezvous with Rama

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Clarke's Rendezvous with Rama, depicting a spacecraft approaching a truncated cone of some kind. Photo credit: pinterest/RickWall
December 24, 2024 at 5:13 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 14: Charles Calvert, Teach Yourself Windows 95 Programming in 21 Days

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Cover of the second edition of Sams' Teach Yourself Windows 95 Programming in 21 Days, by Charles Calvert. Two price stickers are visible: reduced from $53.99 to $27, and then to $16.99. Photo credit: Internet Archive
December 23, 2024 at 1:52 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 13: Terry Pratchett, Guards! Guards!

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
#GNUTerryPratchett
Paperback edition of pterry's Guards! Guards!, a Discworld novel. Photo credit: readanybook
December 22, 2024 at 1:44 AM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 12: Carl Sagan, Contact

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Carl Sagan's Contact, with the "now a major motion picture" blurb. Photo credit: Goodreads
December 20, 2024 at 9:52 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 11: Ed Tittel, HTML 4 For Dummies

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of HTML 4 For Dummies, by Ed Tittel and Stephen Nelson James, with included CD of source code. Photo credit: James O'Neill, freexenon.com
December 19, 2024 at 9:56 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 10: Raymond E Feist, Magician

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback "new revised" edition of Raymond E Feist's Magician. Photo credit: World of Books, Germany
December 18, 2024 at 8:47 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 9: Iain M Banks, Excession

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#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Iain M Banks' Excession, on brown paper backing. Photo credit: a now unlisted item on Etsy
December 17, 2024 at 9:07 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 8: JRR Tolkien, The Lord of the Rings

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
#LotR
Paperback single-volume edition of Tolkien's The Lord of the Rings, stood on end to show the phat spine. Photo credit: Stella & Rose's Books, Tintern
December 16, 2024 at 9:27 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 7: Larry Niven, Ringworld

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Larry Niven's Ringworld, in a plastic dust jacket, on grey carpet. Photo credit: Ok, this one's mine
December 15, 2024 at 9:29 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 6: Isaac Asimov, Foundation

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of Isaac Asimov's Foundation collection of shorts. Photo credit: flickr/ra.az
December 14, 2024 at 9:05 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 5: David Eddings, Domes of Fire

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of David Eddings' Domes of Fire, book one of the Tamuli trilogy. Photo credit: Anthony Bonner, anthonyzuri.blog
December 13, 2024 at 10:08 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 4: Commodore 64 Programmer's Reference Guide

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
The C64 Programmer's Reference Guide, with plastic-tooth binding. The fold-out electronic schematic can just be seen poking out the back. Photo credit: RavenWolf's retro-tech shop
December 12, 2024 at 9:01 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 3: JRR Tolkien, The Hobbit

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Art project to create a book cover for JRR Tolkien's The Hobbit. Credit: deviantart/dreams-design
December 11, 2024 at 10:31 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers.

Day 2: MS-DOS 5 User's Guide and Reference

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Microsoft MS-DOS Operating System version 5.0 User's Guide and Reference in glorious monochrome, on a grey laminate floor. Photo credit: somewhere on eBay
December 10, 2024 at 9:55 PM
imrannazar.com
Choose 20 books that have stayed with you or influenced you. One book per day for 20 days, in no particular order. No explanations, no reviews, just covers. (Cheating a little, as I did this on Mastodon already)

Day 1: A Wrinkle in Time

#BookSky💙📚
#Books
#BookChallenge
#20DayBookChallenge
Paperback edition of A Wrinkle in Time by Madeleine L'Engle, on a wooden table. Photo credit: pinterest/emilyrenee5
December 9, 2024 at 6:15 PM
imrannazar.com
If anyone ever asks you "Why was the C64's disk drive so slow?", now you'll have an answer. A full list of sources for this tale is in the alt text; do drop me a note if you have any questions about the (even) finer technical details. Merry Christmas. 100/100
A macro shot of the "64" end of the C64 case logo. Sources used in this thread: David Callan's on the 1541: https://www.lemon64.com/forum/viewtopic.php?p=628303&sid=36540ed1a6aa32e4c4d28b336d1fcff4#p628303 "A Brief History of the IEC Bus" by Jim Butterfield, as compiled by Jan Derogee: https://retro-bobbel.de/zimmers/cbm/programming/serial-bus.pdf CBM Disk Transfer Benchmark, Brandon Staggs: https://www.obliterator918.com/dtb/ PET 2040 disk drive, Dave's Old Computers: http://dunfield.classiccmp.org/pet/index.htm KIM-1 and Apple-II 6522 breakout photos, Hans Otten: http://retro.hansotten.nl/6502-sbc/kim-1-manuals-and-software/ Tale of the Ultimax, Greater Pittsburgh Vintage Computer Museum: https://www.myoldcomputers.com/museum/computers/commodore_vic20.htm Making the CES Show, Bil Herd, at Hackaday: https://hackaday.com/2015/01/10/making-the-ces-show-thirty-years-ago/ 6522 shift register traces, Nigel Cleaver: https://electronicsadventures.blogspot.com/2020/05/6522-versatile-interface-adapter.html Basics of Analog Video, Analog Devices: https://www.analog.com/en/resources/technical-articles/basics-of-analog-video.html Section 13.5 of the K12 Physics textbook at Libretexts: https://k12.libretexts.org/Bookshelves/Science_and_Technology/Physics/13:_Electromagnetic_Radiation/13.05:_Photoelectric_Effect Reimplementation of monochrome PAL, Batsocks: https://www.batsocks.co.uk/readme/video_timing.htm How the VIC20 Works, Tynemouth Software: http://blog.tynemouthsoftware.co.uk/2019/09/how-the-vic20-works.html VIC-20 video timings, Jon Brawn: https://www.brawn.org/VIC-20/Video/video.html C64 mainboard photos, Marc-Jano Knopp: https://ist.uwaterloo.ca/~schepers/MJK/c64__.html The downfall of Commodore, Bradford Morgan White: https://www.abortretry.fail/p/the-history-of-commodore-part-4 And, of course, the unparalleled Wikimedia commons: https://en.wikipedia.org/
December 2, 2024 at 11:43 AM
imrannazar.com
If we count up the time taken by the instructions in the relevant section of this disassembly, we find it takes at least 19μs to read in a single bit from the serial bus; with the surrounding code, it can be more like 500μs to read a full byte, before the rest of the OS even sees it. 89/
A section of the disasembly of the VIC-20 ROM, with annotation comments. The code reads as follows: LSR ; serial data into carry ROR LAB_A4 ; shift data bit into receive byte LAB_EF66 LDA LAB_911F ; get VIA 1 DRA, no handshake CMP LAB_911F ; compare with self BNE LAB_EF66 ; loop if changing LSR ; serial clock into carry BCS LAB_EF66 ; loop while serial clock high DEC LAB_A5 ; decrement serial bus bit count
December 2, 2024 at 11:43 AM
imrannazar.com
Fortunately, this problem was found before the hardware was finalised, so there was time for a hack: every eight lines, the VIC signals to the CPU that it's taking over the memory bus, and the CPU isn't allowed to do any work for 40 cycles. 84/
Schematic diagram of the C64 (this particular schematic is of the C64c from 1991), with a red line highlighting the AEC trace from the VIC to the CPU. Credit: Marko Mäkelä
December 2, 2024 at 11:43 AM
imrannazar.com
So that's what they did: build a 12-bit cache for the screen and colour RAM values onto the VIC-II silicon, and push everything else around to compensate. The video chip uses this cached copy of the screen to index the character generator ROM and work out which shapes to draw. 82/
A die shot of the unlidded VIC-II (a later model in this case, the 8565), with a red box drawn around the 12x40-bit screen cache in the bottom left. Credit: Michael Steil, via Visual6502
December 2, 2024 at 11:43 AM
imrannazar.com
The VIC has 16 colours: every unique combination can be expressed in four bits. Colour RAM on the VIC-20 isn't the normal eight-bit memory of the rest of the machine, it's four-bit RAM, and the VIC chip itself has a combined 12-bit data bus to read from both types of memory at once. 76/
The schematic diagram of the VIC-20 from post 37, with two additional highlights: an eight-bit data bus leading to general memory in green, and a four-bit data bus specially for colour RAM highlighted in blue. Credit: Tynemouth Software
December 2, 2024 at 11:43 AM