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ec1842 (not in MESS -- not sure if there are any dumps) is another interesting (aka horrible) beast -- it was apparently designed to run protected-mode OS for i286 (not sure if it was an original design or not).

But instead of i286 or its clone it uses a modified i8086 + external MMU + software emulator for opcodes that aren't implemented in the silicon.

The emulator -- http://zx.pk.ru/attachment.php?attachmentid=46992&d=1395679442

Ongoing discussion -- http://www.phantom.sannata.ru/forum/index.php?t=15452

Spent a few minutes looking and don't think there's a simple way with normal PC raw floppy images. You'd probably have to make an imagedisk file with bin2imd with the correct layout options.

Will try that, thanks.

poisk1 and mc1502 also have a QD drive but can handle both QD and DD floppies (the former checks media descriptor, the latter just creates two more logical drive letters).

I want to use 720k floppies in ec1841 emulator.

When "dip switches -> floppy type" configuration switch is in "40 tracks" position, then only 360k disks work. After loading pu_1700 I'm able to format empty 720k image to 80 tracks/ 9 sectors/ 2 heads, but then I have sector error on any access above 360k.

When "dip switches -> floppy type" option is "80 tracks", then I'm not able to make bootable DOS image at all. I've tried to make 360k, 720k, 1.2m images in different ways, in "80 tracks" mode DOS doesn't boot, sometimes prints "Disk Boot failure", which means that 1st sector is read, but not more.

What should be the value of that "floppy type" configuration switch?

I don't think it is actually used by the BIOS. I implemented it only because the available tech manual documents it.

BTW, the poisk1 BIOS wants media descriptor byte to be F9 on 720k floppies or they won't boot.

shattered, than you for reply, though it's confusing, because there is a difference in behaviour depending on this switch position.

I have a bunch of plain floppy images:

copies of real floppies,
or downloaded from internet,
or prepared by dd count=$((9*2*$ntracks)) and then formatted from within emulator or mapped and formatted as loop device in linux etc etc.

All these images work fine when they are 360 KB _and_ mentioned switch is set to "40 tracks".

None of these images (of any size) are recognized when your switch is set to "80 tracks".
I've tried to set media descriptor byte (at 0x15 offset) to F9 (most 720k images already has it), without success.


All I want is to emulate authentic DS/DD floppies, which were most commonly used on 1841 and usually formatted to 80/2/9 CHS (720 KB).
Is this possible, did you try this?

ec1841 driver is configured with DSDD drives, not DSQD so even with DIP set to 80, there's no way for this to work. And I'm not sure MESS can autodetect 40/80 tracks (see earlier messages in this thread) even if you change it to DSQD.

So no simple way to have 720 disks?

Afraid so. Maybe attaching a secondary FDC could work.

Hard disk support is more useful, and I should clean up and submit patches to isa_hdc that make it compatible with ec1841. XT-IDE should also work but for some reason doesn't.

Ok, thank you for explanation.