[HN Gopher] How the Final Cartridge III Freezer Works
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How the Final Cartridge III Freezer Works
Author : ingve
Score : 49 points
Date : 2025-06-14 16:57 UTC (6 hours ago)
(HTM) web link (www.pagetable.com)
(TXT) w3m dump (www.pagetable.com)
| michalpleban wrote:
| One important detail the article omits: it is possible for the
| software running on the Commodore 64 to prevent being "frozen" by
| this technique. Because the processor needs the NMI interrupt to
| run the freeze routine, the software can pre-empt it by pulling
| down the NMI line on its own. This can be done using the second
| CIA I/O chip, whose interrupt output pin is connected to the NMI
| line. By making the CIA chip generate the NMI and never
| acknowledging it, the software will ensure that the NMI line is
| always pulled low and the freezer will not work.
| WJW wrote:
| That's a clever trick, but giving up all the useful types of
| NMIs seems like a steep price to pay.
| michalpleban wrote:
| Commodore 64 software hardly ever uses the NMI interrupt,
| because there is also the maskable IRQ interrupt which can be
| generated by the first CIA chip, and also, unlike NMI, by the
| video chip VIC for the raster interrupt. It is also much more
| useful because it is maskable - the software can temporarily
| turn it off when it is not desirable to be interrupted. The
| only thing the NMI can do that IRQ cannot is detecting that
| the Restore key was pressed, but that is seldom useful.
| predictsoft wrote:
| I love how the Action Replay FLOPPY disk for Amiga 1200 loads
| into the high 1MB RAM space. No need for hardware. (note: Amiga
| 1200 has 2MB RAM by default).
| daitangio wrote:
| Very interesting. I was m always amazed by the code complexity
| behind C/64. Also, all this logic was squeezed in so few bytes!
| classichasclass wrote:
| I liked the interface of the FC3, but I always seemed to have
| trouble with it on NTSC systems, likely the fastloader. I ended
| up using ICEPIC or Super Snapshot most of the time instead.
| michalpleban wrote:
| I always found Action Replay to be superior and easier to use
| than Final Cartridge.
| TMWNN wrote:
| I presume that the lack of an Ultimax-style bypass is why, as I
| understand it, there are no freezer cartridges for Atari 8-bit.
| (The piracy problem was just as bad, however, because of Happy
| Computers <https://en.wikipedia.org/wiki/Happy_drives>.)
|
| On the other hand, Atari 8-bit's design allows for FujiNet to
| work without the workarounds/disadvantages a Commodore equivalent
| would have. <https://news.ycombinator.com/item?id=37424773>
| spacedcowboy wrote:
| There were freezer's for the Atari line. They plugged into the
| parallel bus IIRC.
|
| I never owned one, I only know because I've just spent the last
| 3 or 4 days putting together a site to browse my mirror of
| pigwa.net (the Atari software archive site), and I happened to
| be using the 'Projects' directory for my testing.
|
| If you:
|
| 1) go to http://atari-archive.net/
|
| 2) Double-click the 'Cloud drive' icon to open the window
|
| 3) Double-click on 'Projects', then 'Turbo Freezer 2005 & 2011'
| [1]
|
| You can see the project, including a PDF of English
| documentation in the turbo-freezer-2011 subfolder.
|
| [1] The icon isn't wide enough for the entire filename but it's
| obvious what's what. There's an 'As list' mode if it bothers
| you :)
|
| I think the Atari version uses the /IRQ on the parallel bus, I
| know you can do some funky stuff with that - like take over the
| bus from the CPU (by keeping it in halt) and as long as you
| respect Antic's bus cycles (the true master of the "cpu" bus)
| you can read/write to RAM and do whatever you want.
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(page generated 2025-06-14 23:00 UTC)