Cheap chinese floppy emulators & Lafumat's disk controller
Posted: Sun Apr 21, 2013 3:59 am
So... I bought one of those...
http://www.ebay.com/itm/230910971956
...with the intent of using it with my many vintage computers. Hey, it costs a fraction of the (admittedly kickass) Lotharek alternative. The first guinea pig was the MSX, and it worked perfectly, after some judicious jumper selecting. (Set as drive 0, fudge with READY timing.) As a curiosity, here's my blog posts (in Portuguese) about the subject:
http://www.retrocomputaria.com.br/plus/?p=3295
http://www.retrocomputaria.com.br/plus/?p=3610
One complication I didn't have then is the MSX wants 512 byte sectors in its disks, just like the PC. That made things easy. With the Dragon, which uses 256-byte sectors, I knew it would not be so simple. I started by using the same jumper settings. So far so good. It looked like DragonDOS recognized a drive. DIR gave me ?IV ERROR and lit up the access light on the emulator. Sweet.
But DSKINIT didn't work. Even with only one face and 40 tracks, I would get a "record not found" error. So I started reading and writing individual sectors with SREAD and SWRITE.
Turns out I can read/write only nine sectors per track, and DragonDOS wants 18 in all formats. Bleh. I made a program to write a string "T xx S yy IMG zz" in every (writable) sector of the virtual disk. Take a look at this album:
http://picasaweb.google.com/11627422826 ... orOnDragon
I ran this program on images 0 and 1. A compressed version of the data partition is here. Beware -- it's 159K compressed, but 151 megabytes uncompressed! It corresponds with what the emulator does in a MSX or a PC, with the following differences:
One: Each 512-byte sector in the image has, in the first 256 bytes, what I really intended to write in that sector. The other 256 bytes have a copy of what was previously written in the last sector!
Two: After every 9 sectors, there's 9 sectors of nothing. I assume if the emulator were capable of writing sectors 10 through 18 in each track, they would lie there. Also, one face only.
Three: Each image lies 1.5MB apart, just like with the MSX.
Then it hit me. I bought a 720K model of the emulator, for compatibility with the MSX. But 1.44 MB DISKS HAVE 18 SECTOR PER TRACK!
There's a jumper in the emulator which, in theory, would switch it from 720K to 1.44M. But if you select it, the computer can't read anything. On the other hand, there's a 1.44MB specific model from the same seller and manufacturer, and it's even cheaper:
http://www.ebay.com/itm/230935796270
Maybe I should buy one to experiment. I'll wait until Good Credit Card Day, which is in a few days. Unless someone wants to donate me one... you know, for Science!
http://www.ebay.com/itm/230910971956
...with the intent of using it with my many vintage computers. Hey, it costs a fraction of the (admittedly kickass) Lotharek alternative. The first guinea pig was the MSX, and it worked perfectly, after some judicious jumper selecting. (Set as drive 0, fudge with READY timing.) As a curiosity, here's my blog posts (in Portuguese) about the subject:
http://www.retrocomputaria.com.br/plus/?p=3295
http://www.retrocomputaria.com.br/plus/?p=3610
One complication I didn't have then is the MSX wants 512 byte sectors in its disks, just like the PC. That made things easy. With the Dragon, which uses 256-byte sectors, I knew it would not be so simple. I started by using the same jumper settings. So far so good. It looked like DragonDOS recognized a drive. DIR gave me ?IV ERROR and lit up the access light on the emulator. Sweet.
But DSKINIT didn't work. Even with only one face and 40 tracks, I would get a "record not found" error. So I started reading and writing individual sectors with SREAD and SWRITE.
Turns out I can read/write only nine sectors per track, and DragonDOS wants 18 in all formats. Bleh. I made a program to write a string "T xx S yy IMG zz" in every (writable) sector of the virtual disk. Take a look at this album:
http://picasaweb.google.com/11627422826 ... orOnDragon
I ran this program on images 0 and 1. A compressed version of the data partition is here. Beware -- it's 159K compressed, but 151 megabytes uncompressed! It corresponds with what the emulator does in a MSX or a PC, with the following differences:
One: Each 512-byte sector in the image has, in the first 256 bytes, what I really intended to write in that sector. The other 256 bytes have a copy of what was previously written in the last sector!
Two: After every 9 sectors, there's 9 sectors of nothing. I assume if the emulator were capable of writing sectors 10 through 18 in each track, they would lie there. Also, one face only.
Three: Each image lies 1.5MB apart, just like with the MSX.
Then it hit me. I bought a 720K model of the emulator, for compatibility with the MSX. But 1.44 MB DISKS HAVE 18 SECTOR PER TRACK!
There's a jumper in the emulator which, in theory, would switch it from 720K to 1.44M. But if you select it, the computer can't read anything. On the other hand, there's a 1.44MB specific model from the same seller and manufacturer, and it's even cheaper:
http://www.ebay.com/itm/230935796270
Maybe I should buy one to experiment. I'll wait until Good Credit Card Day, which is in a few days. Unless someone wants to donate me one... you know, for Science!