Running on real hardware

[Antti]

I had a chance to run my OS (a boot loader actually) on several real computers. I was surprised to see how many problems I got. None of them was a real bug in the strict sense but caused serious problems. Just to name a few that I recently fixed:

- One computer disabled interrupts when using INT 13h Extensions. I was not expecting this.

- One computer always returned zero in reserved mask size and position when getting a VBE mode information structure although there were such bits.

- At first I thought it would be enough to support just non-palette VBE video modes but on older real computers this would have been a problem. I found that I get much better resolutions if I support palette modes also. One computer I tested only had reasonable resolutions if using 8-bit colors.

I think making an OS and testing it only on an emulator is very far from having a real OS. I dare to say "emulator OSs" would have a high probability of failing if tested massively (e.g. 1000 computers) on real hardware. Why am I complaining? I do not know. Just keep testing on different computers as much as you can if you want to have something that really works.

[bluemoon]

Yes, to name a few common issues:
- memory was assumed to be zero and worked on emulators (BSS not zero'd).
- probably everyone has encountered issue with assuming certain hardware exists, like PS2 controller, or an VGA, or keyboard.
- booting takes forever long when using BIOS to load 2MB files from an USB stick - which enforce me to do disk caches in boot loader that half the boot time.
- without USB support yet, unable to do anything with the usb keyboard.

[Combuster]

Not to mention that all the common emulators out there have very limited video emulation.

But we have a solution to all that since ages: Revival of the test beds?

[Hoozim]

I know what you mean! I do the majority of testing on real hardware just because I have plenty available and I feel like my OS is a lot more "legit" if I run it on real hardware. Drivers though are the real pain in the neck. Not long ago I bought a brand new netbook which has since become my new testbed, replacing my old 2000 PC as a testbed. I ran across a number of problems. My keyboard driver had to be reworked, only 1 nights work but still had to be updated. At the moment, I have to figure out why my EHCI/USB driver isn't working, could take a while.

Jacob

[rdos]

Right, emulator-only OSes hardly should be called OSes at all. In order to qualify, they should run at least on one real machine.