The "overlay 1" .iso from https://winworldpc.com/product/irix/6522, (...) is corrupt. Can I somehow skip this file and somehow make or get a hard disk image that has Irix already installed?
You might want to try marking it read only on the host OS. I believe these old IRIX install discs use a non-standard format so even a good image won't mount using regular methods. It's also definitely possible the image is corrupted so I'll investigate to see if I can get it working some time soon. For a pre-made IRIX 5.3 or 6.5.22 image please see the links on the front page.
I really wish to contribute with some money to keep this project going! How to donate?
Please send all donations to either the IRIX Network Forums (http://forums.irixnet.org/) who host the bulk of the files and discussion around SGI hardware and software, or to the MAME project (https://www.mamedev.org/) who are responsible for the development of the actual emulator.
What are the next steps for the project? How many developers are working on it?
MAME is developed by volunteers so it's entirely up to them if/when work on the SGI drivers is done. MAME is open source software so presumably anyone would be free to study the source, submit code or create a fork. The number of people working on SGI emulation specifically is probably a dozen or two. As of June 2021 the indy_indigo2.cpp file on GitHub lists 14 contributors with the latest commmit being a couple weeks old.
Would the indigo2 port run faster than the indy one?
The Indy is faster. I think this is because the emulated CPU is clocked lower, making the emulation less taxing on the host system. The Indigo2 doesn't offer anything special aside from the dual head option, though this is at the cost of speed. On my Ryzen 5 3600 workstation with Debian I can get around 25-35% of the speed of a real Indy. The Indigo2 with dual graphics boards runs at around 15-20%.
Can you tell me how you can run IRIX 5.3? Do I need to use the same files (ps2_keybc.zip, ip24prom.070-9101-011.bin) or some others? Where can I get a disk image with IRIX 5.3 installed?
I've updated the file list to include a link to a pre-made disk image with IRIX 5.3. Just follow the guide above to run it by replacing the disk image name in the commands. You will need the same PROM files and commands. I will work on a guide for installing 5.3 from scratch soon but for now the existing install guide should be helpful for creating a blank disk image.
How can I extract resources from this? I want the icons and backdrops out of IRIX.
I'm not sure where they're located but everything you're looking for should be on the pre-made disk image. MAME now supports networking on Linux and Windows and some users have been able to get online with IRIX. This would probably be your best bet for getting files off the emulated Indy. If you take a look at the internal site links above I've already cropped and uploaded some of the stock wallpapers.
Hey the link to the IRIX disk image returns a 404 for me, but the wayback machine version works fine.
It may have been a temporary issue with the host but this seems to be resolved now. As of writing this all of the links up top are working. Thank you for letting me know. I'll be sure to check them periodically and fix any that become broken. I've also added an install guide so that you can make a fresh disk image on your own if needed.
Is there any way to improve the performance of the emulation (speed/clock) and if so, how?
Buying better hardware is probably not the answer you were looking for but the alternatives have some downsides. MAME will allow you to decrease the clock speed which can help a bit with graphics. Or you can enable frame skipping for worse graphics but faster CPU performance. I recommend the latter if you want to explore the OS and open programs without waiting several minutes, though the visual experience will be poor.