[Coco] [COCO] MAME FDC Issue that can cause corruption

David Ladd davidwladd at gmail.com
Tue Aug 1 01:50:32 EDT 2017

Dear MAME users,

Over the last couple months I have been doing a LOT of disk testing and
stuff with emulators, but is even more scary than I thought 2 months ago.

I just found out tonight that MAME does indeed have a issue related to the
FDC emulation.  I can reproduce the issue in NitrOS-9 L1/L2 or OS-9 L1/L2.
I have even been able to re-produce some stuff in Disk Basic.

Till this issue is fixed I would recommend to not use more than 1 floppy
drive in MAME.
If you want to try it out the simplest way to show this off is to do this:
Startup CoCo 2 or CoCo3 emulation
Create a new disk image in drive 0
Create a new disk image in drive 1
Enter a quick basic program like this and save it to disk:
10 PRINT "DIR 0"
20 DIR 0
30 PRINT "DIR 1"
40 DIR 1
50 GOTO 10

Then all you have to do to see the problem is to:

You will see TEST1.BAS show up twice.  Which it should not.

So please take heed that this can cause corruption if data is written to
both drives at same time.  I found this out the hard way tonight.

I am also going to clarify I am doing this just as a warning.  I am not
trying to scare people away from MAME or say one emulator is better than
another one.  I just want people to take heed with this issue till the
problem has been addressed.

Also the more people who can also verify this problem and report it to the
development website for MAME might also help motivate the dev team to fix
the issue as well.

Thank you for your time with reading this.

| David Ladd a.k.a. PacoOtaktay a.k.a. Drencor                          |
| YouTube: http://www.youtube.com/user/PacoOtaktay                      |
| YouTube Gaming Live: https://gaming.youtube.com/user/PacoOtaktay/live |
| Websites: http://dwladd.com     &     http://www.theterrorzone.com    |
| G+:  https://plus.google.com/113262444659438038657                    |
| G+:  https://plus.google.com/+DavidLaddPacoOtaktay                    |
|                                                                       |
| Do you have your CoCo 3 yet?                                          |

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