Thank you, Eric! -I will do some testing of reading the CF card outside of the FreeDOS kernel, as you suggest. -My BIOS supports both CHS and LBA. FreeDOS is using CHS due to the size of the CF card (~500MB). I will try forcing LBA. -I log interrupt calls out to my serial debugger on my 286. In execrh(), I am not seeing any INT13H calls get called. -I will need to learn more about disk I/O drivers. I assume for the IDE CF Card, that driver is part of the FreeDOS kernel code. If I wanted to add some debug code to the driver, where should I look to find the driver source code? I see a "drivers" folder in the source, but the only thing that looks related is floppy.asm. I can try adding some logging code in this file. -My system does not support DMA at this stage. I am using PIO mode only. -I have my system running quite slowly (8MHz system bus, 4MHz processor clock) at this stage.
I have updated the following post with additional details: https://www.rehsdonline.com/post/troubleshooting-freedos-boot-on-my-286-syst em-hangs-on-execrh-call-in-kernel. I will continue to update this as I (hopefully) progress in this troubleshooting. I appreciate all the suggestions. Thank you again, Eric! Rich -----Original Message----- From: Eric Auer <e.a...@jpberlin.de> Sent: Friday, May 5, 2023 3:07 AM To: freedos-devel@lists.sourceforge.net Subject: Re: [Freedos-devel] trying to understand execrh.asm -- calls to EXECRH cause my 286 system to lock up Hi Rich, > I am trying to better understand the EXECRH function in execrh.asm > <https://github.com/FDOS/kernel/blob/66df13c4d867b49558a85929a13432df6 > 3cf5ac 0/kernel/execrh.asm> . Could someone help me understand the > call being made in EXECRH of "call far[.dhp]"? To where is it > calling, and should I have done something in my BIOS or elsewhere to > support this call? > > Additional Details: During boot on my 286 build the system hangs... > * The rqblockio() function then calls execrh() [execrh.asm]. Well, this is how the kernel calls drivers. Apart from the detail that it does STI, CLD as a side effect, which should not disturb other parts of the kernel, it will call some kind of disk I/O driver in the context you describe. You write that you use a custom built BIOS for your 286, and a compact flash card on IDE adapter as drive. So I suggest that you do some testing of the BIOS itself, without DOS. You could write a small test case and install it as boot sector. Maybe the BIOS has issues with the mentioned flag changes or maybe it simply does not yet have sufficiently foolproof disk error handling, so it fails when there is more disk access? Does the BIOS support both CHS and LBA? Which one is used for booting? You can pass options to SYS to force one of the other and you can use SYS CONFIG to patch the kernel to force that as well. It might also be some issue related to stack usage, DMA or the address ranges used by DOS, disk I/O and maybe other drivers? Interesting project in any case, I like to hear about your progress when you got FreeDOS to boot on your custom BIOS! Regards, Eric PS: CF cards in the past were meant to access few, large files. So they had few I/O per seconds. Sometimes they had hiccups. _______________________________________________ Freedos-devel mailing list Freedos-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-devel
