Top all-time · #9351
Jakob Engbloms
Personal blog · jakob.engbloms.seprogramminghardware
Jakob Engbloms writes Observations from Uppsala, a personal blog at jakob.engbloms.se about programming and hardware. Since 2009, 8 different Hacker News readers have linked it 17 times. It is still writing: the last post was on 2026-10-11, and you can follow it by feed.
Too few sampled comments (3) to say how often HN recommends it.?
Why HN links it
HN readers link his posts for surveys of time-travelling and reverse debuggers and for lists of FPGA-based retro hardware emulation projects. The comments cite these posts as sources and resources.
Summarised by Claude from a sample of 3 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Most-linked posts?
- /archives/15642 people · 4 mentions · first linked 2021-05-13
What Hacker News says?
rr was introduced in 2014 [1]. gdb reverse debugging was introduced in 2009 [2]. You can see a fairly comprehensive history of time travel debugging here [3]. Not to say the built-in gdb reverse debugging was any good. It had (has?) like 1,000,000% overhead which is basically unusable. At least some implementations in the history that were introduced earlier only had ~1,000% overhead or less in general. Yes, a liter…
Comment linking /archives/1564
on “rr – record and replay debugger for C/C++”Submitted “The Mill” – It just might Work as a story · 274 points
HN discussionA brief survey of time-travelling debuggers[1]. What [1] does not note is that it was heavily studied in relation to Prolog in the late 80s and early 90s. Some very fancy shenanigans were possible including scripts watching variable bindings and actions. Some of this becomes evident if the Pancake bibliography is scanned[2]. It's exciting seeing the dream of the 70s come alive. :-) [1] http://jakob.engbloms.se/archi…
Comment linking /archives/1554
on “Elm's Time-Traveling Debugger”Submitted C in Danger (and thus Higher-Level Languages?) as a story · 48 points
HN discussionWild. Apparently there are many different efforts to use FPGAs to simulate old hardware: "Using FPGAs to Simulate old Game Consoles": https://jakob.engbloms.se/archives/3026 "AMSTRAD ON AN FPGA": https://hackaday.com/2017/01/06/amstrad-on-an-fpga/ "MISTER FPGA: THE FUTURE OF RETRO GAME EMULATION AND PRESERVATION?": https://www.racketboy.com/retro/mister-fpga-the-future-of-re...
Comment linking /archives/3026
on “First new VAX in 30 years?”Submitted Why do computers fail? as a story · 2 points
HN discussionThe archived page claims they started in 2013. Time travel debugging was commercially available (by other vendors [1]) for over a decade by that point. [1] https://jakob.engbloms.se/archives/1564
Comment linking /archives/1564
on “RAD Debugger”Submitted Joel Spolsky: You cannot program parallel in C, period as a story · 1 points
HN discussionThis is just standard instruction trace. Intel has supported such capability via Intel Processor Trace (PT) since at least 2014 [1]. Here is a full trace recorder built by Jane Street feeding into standard program trace visualizers [2]. ARM has supported such capability via the standard CoreSight Program Trace Macrocell (PTM)[3]/Embedded Trace Macrocell (ETM)[4] since at least 2000. If you pair it with standard data…
Comment linking /archives/1564
on “Apple's new Processor Trace instrument is incredible”A history of other time traveling debugging papers and products (including this one): https://jakob.engbloms.se/archives/1554 https://jakob.engbloms.se/archives/1564
Comment linking /archives/1564
on “Debugging operating systems with time-traveling virtual machines (2005) [pdf]”No, time travel debugging is almost certainly a root, but comes from a different lineage. https://jakob.engbloms.se/archives/1564 The Green Hills Software Time Machine product for time travel debugging was commercially available by September 2003 [1] which is at least contemporaneous with that paper by Bill Lewis (i.e. terminology could not have been derived from it). Given the alternative terminology frequently use…
Comment linking /archives/1564
on “Revy – proof-of-concept time-travel debugger for the Bevy game engine”Time travel debugging on embedded ARM has been available for over 20 years via trace probes [1]. The category namer of time-travel debugging, TimeMachine, (hence time-travel debugging in contrast to other attempted names such as reversible, bidirectional, record-replay, etc.) was available in 2003 and supports/supported the ARM7 [2]. Note, that is not ARMv7 architecture, that is the ARM7 chip [3] in use from 1993-20…
Comment linking /archives/1564
on “UndoDB – The interactive time travel debugger for Linux C/C++ for debugging”Time travel debugging is actually the more common historical term for the technology along with replay debugging specifically for the record-replay based variants. Reverse debugging as a term is really more of a GDB-ism and even there the term only really started gaining steam when rr produced a reasonable backend with GDB reverse debugging commands as a front-end. Also, frankly, the original GDB reverse debugging b…
Comment linking /archives/1564
on “55,000 lines of Rust code later: A debugger is born”There is actually a surprising amount of reverse debugging products out there, some are listed here: http://jakob.engbloms.se/archives/1564 Would you be willing to use one of those?
Comment linking /archives/1564
on “Ask HN: Why are we not using debuggers more?”Commercially available time travel debugging is over 20 years old at this point [1]. So yeah, the uptake is pretty slow. [1] http://jakob.engbloms.se/archives/1564
Comment linking /archives/1564
on “Stone Knives and Bear Skins – There is no money in tools”This is a class of tools called time travel debuggers. Here is a little history of them: http://jakob.engbloms.se/archives/1564 Generally speaking we do not see much mention of them because the technology involved is reasonably tricky to develop and software developers and companies are as a rule penny wise, but pound foolish with respect to tooling. So, there is very little money in actually expending the developme…
Comment linking /archives/1564
on “Omniscient Debugging”