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    It’s not guessing at a 2:1 compression ratio, like Salient’s AutoDoubler and DiskDoubler (now owned by Symantec) — you actually see your total memory being twice your built-in memory.

    Huh? They’ve invented a compression algorithm that can guarantee 2:1 compression? What if you run it twice?

    Of course, later they go on to explain a bit more, with the rather important caveat that it doesn’t help much running a single large app like photoshop. So it’s not a guess, it’s just sometimes wrong?

    I guess it’s rather late to complain about a 25 year old article, but I’m still disappointed. So much for the theory that tech journalism used to be good. :(

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      Once I read it required a 68030, I knew how it worked—paging. The 68030 included the 68851 Paged Memory Management Unit built in.

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        Not so much that. If RD can’t achieve the guaranteed amount of virtual RAM by stealing from other apps or by compression, then it resorts to swapping like any other VMM. So you’ll get it with a hog like Photoshop running, but it may take a hit in the process.

        Source: my 1400+G3/466 with 9.1 and RAMDoubler 9, which really needs it since the 1400 is limited to 64MB

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        John Gruber wouldn’t go so far out of his way to not subtly imply that this openness was somehow endemic to Mac only. But MS-DOS was exactly like that, and I’ll hazard a guess that most of the OSes of the 80s were like that.

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          The Mac was in a somewhat unusual situation where the OS provided high-level APIs, and most applications used them because the actual hardware varied from machine to machine. Contrast this with MS-DOS, where the OS (or the BIOS) provided high-level APIs that people generally ignored because you could get better performance by bit-banging the VGA registers yourself.

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            This is true for graphics, for which there was no powerful API. But for things like opening files and writing text to the output you still used common work horses like int 13h / int 21h.

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          So if this worked so well and was truly effective, how come it isn’t a standard feature of modern operating systems? Or is it perhaps? Linux has zswap but I’ve never seen it used. From a brief read it seems the use is as much about avoiding wear of flash used for swap on embedded systems than about making RAM go further.

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            macOS has performed memory compression since OS X 10.9 Mavericks, which was released in 2013. For example, the Activity Monitor currently tells me that my Calendar app is using 193.4 MB of “memory”, of which 133.4 MB is “compressed memory”. (I’m not sure how those figures relate to the real, private, shared, and purgeable memory figures also shown.)

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                I’ve been using zram on linux to great effect.

                First started when I was using a computer with a broken harddisk for a week. Booted to ram from a usb drive, and used zram to make my 8gb of ram stretch much further (worked surprisingly well all things considered).

                Now I basically just always have it on, very convenient for things that use to bring my computer to a halt because they ran out of memory and swap is insanely slow.