I haven't looked into it myself, but I read some people noticed installers at one point which were using zlib compressed files within the installer, which was still being compressed with lzma2 as far as inno setup was concerned (can't remember the thread right now).

Is it "official" that they've switched only to zlib based compression on the new installers that are showing up these days?

Edit: Nevermind, found your original reply on this matter :).

To share my views on it, yes zlib is faster, but I think lzma is as fast today as zlib/deflate was back when everyone appreciated its speed. We have a lot more processing power under the hood these days, and since lzma2 now is multi-threading capable on decompression as well, I think the better compression ratio it provides would be an offer hard to refuse. Think of all the people with limited bandwidth that would benefit immensely from this - I don't think they'd mind an extra 30 seconds of installation time if they save up 10-20 minutes of download time.

The estimates I've seen in terms of memory usage during 7-Zip decompression alone did not go above 100MBs even on Ultra. This was before multi-threaded decompression was added mind you, but I expect it to scale more or less linearly. Even with some memory overhead from the installer itself, it shouldn't be a problem for any system that can run Windows 7 :).

The decompression routine will "take as much as it can" to run as fast as it can, I think, but it will work even in situations where limited RAM is available.

Raise the Dictionary size... The 'Ultra' is just a preset.

Is it still supported? I know official support for Windows 7 ended a while back. No bueno being on an OS that isn't officially supported, and Win10 is free, so...

Unofficially still free to upgrade, but Win10 is a spyware hell with less user control, so.. no thanks.
Btw, Win7 is still receiving patches (even if buggy like all the others released by MS this year).

i would be really surprised if the speed improvements for lzma allow it to come even somewhat close to zlib. zlib is just faster by a lot, especially if you take decompression and compression speed into account.
though there are other new modern codecs that aim at the same application profile as zlib: fast and moderately well compression.
e.g.: brotli, zstd and lz5
these probably would make a better alternative.

that being said, personally I absolutely agree with you. I don't care that much about slower installation. Most of the time I spend on downloading, smaller download sizes would be always preferable to me.
But we had that discussion already a few times about the linux installers. And it seems GOG has already made up their mind to favour speed over size. not sure they are going to change that now *shrug*

the other thing is that games not necessarily compress very well to begin with. Tightly compressed assets will usually give you better loading times (cpu power beats disc IO). Trying to compress these assets further for distribution just means a lot of wasted cpu cycles.
I tried in the past to recompress some linux games for storage and came across a few examples where lzma2 would give nearly zero improvements (iirc trine games for example). In the end when looking at the space saved by recompressing games where it does make a difference vs. the time wasted for games where it does not - I abandoned the whole project because it seemed just not worth it.
(obviously I only tested part of my library, who knows how that would look when testing the whole catalogue)


edit:
there is a fork of 7zip which includes support for the codecs I mentioned above:
https://mcmilk.de/projects/7-Zip-zstd/
it also has some fancy performance graphs for comparison

What do you mean "official"?

Mainstream support for Windows 7 ended in Jan 13th 2015. This means no new features, no free online or phone support etc.

However, MS is delivering security updates to Windows 7 until Jan 14th 2020. So still little over 1½ years of life left.

Fair enough. But it's a preset for a reason - larger dictionaries will not necessarily bring any noticeable improvement in the compression ratio, except in very specific cases, while bumping the memory requirements quite a lot (especially for compression).

Hmm well as long as people bail before security support ends I guess.

I've seen an improvement from 5%-20%, but your mileage may vary depending on content.

I rarely use 7z since WinRAR introduced bigger than 4 MB dictionary sizes in version 5.

I've seen WinRAR to be around 2-3 times faster when compressing and 4-5 times faster when decompressing, compared to 7z LZMA2, both using 256 MB dictionary and word size (and ofc solid archives), while the compression ratio is about 3-5% worse for WinRAR.

Of course, this can depend quite a lot on the content, as I've seen in few occasions where the pre-WinRAR 5 version achieved better compression ratio, with its 4 MB dictionary size, than 7z & WinRAR 5 with 256 MB dictionary size.

Yeah. I'll probably do with this Windows 7 laptop like I've done with my former Windows XP laptops (and a desktop): the original Windows (7) will remain in this, but strictly in offline mode, ie. internet connectivity is disabled. So this will be my "Windows 7 era gaming PC" as long as it runs, running those older games that have issues on Windows 10.

On the side, I might install Linux (Mint) in multiboot mode, in case I or someone else wants to go online with this PC. I have couple such older PCs where I am running both Windows XP (offline) and Linux Mint side by side, in fact they even have Windows 98SE as the third installed OS, but I very rarely need it, ie. that a game wouldn't run ok on XP.

At some point I will buy a newer gaming laptop anyway, and it will have Windows 10 preloaded anyway. Hence I don't necessarily need to upgrade this particular laptop to Windows 10, even though I already have that option too (I registered the free Windows 10 Pro update for this while it was free).

A lot of this is over my head, but from what I can follow, you're saying that GOG is using a different compression method for faster install times. Is that a fair summary? And have any of you actually verified this? Not their motives, I mean, but that they have in fact switched to a different method.

While bzip2 is a bit slower than gzip, it is much faster than xz (at least with the settings I tend to use). And there is a parallel version of it (pbzip2) which is super fast.
Look at lrzip with ZPAQ compression algorithm for top compression (and wait time!).
I wish GOG would use that.