If you were any kind of hacker in Japan during the late eighties or later, you'd have had a hard time staying away from Backup Technique (バックアップ括用テクニック) magazine. Starting with the Famicom, this A5-sized magazine covered nearly every console and computer system available, and was filled with hard and soft hacking, cracking and duplication. It was a magazine that simply had no Western equivalent. 1)
Backup Technique later changed the name to GameLab, a less copyright-offensive title. As GameLab the focus slowly started to shift, as consoles became less and less hacker friendly, from low-level hacking to GameShark codes, modchip information and flashcart reviews.
Both magazines covered anything they considered interesting. For a while BackupTechnique ran a regular column on the Amiga, including the CD32 and CDTV, they touched on the Atari ST and Falcon, and even the Atari Jaguar saw a few mentions. Controller adaptors, rapid-fire schematics, RGB and audio amplifiers, arcade tech before and including the JAMMA standard, home-made superguns (called control boxes) and a whole lot more.
GameLab continues to be published to this day, though it's far less interesting than the old days. Most recent issues are filled with more hentai, porn ads and knockoff controllers than is really palatable. It used to be a fantastic resource, and up to and including the Dreamcast and GBA they included plenty of hacking tips, schematics and resources for the gamers familiar with a soldering iron.
Backup Technique ran for 38 issues (and 2 specials) before changing the name to GameLab. Most of the early issues dealt primarily with the Famicom, and nearly every issue had a new way to copy Disk System games or 'back up' cartridges, defeating the newest copy protection. There was plenty of MSX information as well, as there's little doubt it was the computer platform of choice at the time.
As the series ran on, it covered whatever systems were new and exciting. The PC-8801 and 9801 were included, as well as the X1, X68000, PC DOS/V, TeraDrive, etc. If they weren't talking about sprite hacking or level skipping they covered hard drive installs, floppy wiring diagrams, RGB mods, chip swaps and everything else besides.
GameLab (ゲームラボ) magazine picked up right where BackupTechnique left off, with much the same content at first. As modern consoles became less modifiable the content shifted, the schematics becoming fewer and farther between. The first GameLab was published in the mid nineties, but by 2000 had become far less a useful resource for hackers and more a resource for lonely guys trying to beat dating games, and crack Final Fantasy.
Each issue averaged about 200 pages, and was filled with schematics, diagrams and information, and to a lesser extent reviews and commentary.
Backup Technique mags fetch up to 2,000円 ($20 USD) each, but can typically be found for less than half that.
Both magazines were published by Sansai Books (三才ブックス), a company that seemed to specialize in small, A5 magazines which were more like books published on a schedule.
The A5 format is very popular in Japan, and many specialist magazines are released in this format. Sansai Books offers some almost mainstream titles like Phone Mania and Radio Life as well as counter-culture titles such as 'Dangerous BBS Guide' and a layman's (heh) guide to adult videos.