MiSTer FPGA Forum

Hi everyone! First things first, thank you for making this fantastic core. I'm having a lot of fun experimenting with what an original XT machine can do.

I tried to look on this forum for the same topic without success.

Certain floppy images (720K images to be exact) do not work well with the core: they give a general failure error when trying to access certain files. They do work in DosBox though, and I can access them with my modern computer just fine.

I am running the Tandy BIOS with Tandy-branded DOS 3.30, but the same issue happens with the original IBM bios and non-branded DOS.

Is this a limitation of the original hardware, or it could be that the images are made with a later version of DOS and are thus incompatible?

Thank you!

It's a BIOS limitation. From the core's documentation:

pcxt wrote:

On IBM 5160 or Tandy 1000 only 360Kb images work well.
On Micro8088 only 720Kb and 1.44Mb images work properly.

Just install what you want to run in an HDD and it will work fine.

I'm not sure if it's possible to install every floppy to hard drive - eg PC Booters?

I also had problems with running even 360kb images on 5160 as per this post.

akeley wrote: ↑Sat Mar 18, 2023 4:51 am

I'm not sure if it's possible to install every floppy to hard drive - eg PC Booters?

For that you can just switch the BIOS to match. Is there a specific one that is not usable?

I split my floppies in different folders by file size, so I don't have to guess the size when loading one.

For games with Tandy fx you can only use Tandy bios, and there are quite a few floppy-only ones. Similar case if you'd like to have an authentic 5160 experience.

Some examples are the DOS images I mention in the linked post, and some Tandy I tried for my Tandy pack like Marble Madness, Demon's Forge, or Mozart.

Many games do work ok and in this particular case it's hard to say with just a quick glance whether the fault is with floppy implementation, core bug, or the floppy images themselves (they do work in PCem).

EDIT: actually, MM does not work in PCem, Demon's Forge is a 180kb image. So for now examples of not working ones would be Mozart and Defender Of the Crown.

Newsdee wrote: ↑Sat Mar 18, 2023 3:13 am

It's a BIOS limitation. From the core's documentation:

pcxt wrote:

On IBM 5160 or Tandy 1000 only 360Kb images work well.
On Micro8088 only 720Kb and 1.44Mb images work properly.

Just install what you want to run in an HDD and it will work fine.

Oh I must have missed that bit. That explains everything, thanks!