J. David Bryan wrote: Excellent. Thanx! Again, exactly what I was after. Thanx! The mentioned pdf only covers the old format then, correct? Where can I find docs on the new format? -- Tim Riker - http://Rikers.org/ - TimR at Debian.org Embedded Linux Technologist - http://eLinux.org/ BZFlag maintainer - http://BZFlag.org/ - for fun!

Hey Guys, I'm looking for a BACI board for my HP2100. I'd be willing to trade a MicroCircuit, High Speed Interface, HPIB, or other HP2100 board for one. If anyone is willing to trade, please let me know. Thanks, Steve Robertson steerex [at] ccvn [dot] com

Hi All I thought I'd talk about some of the fun I've been having to recover images from some disk. The disk are 5.25 double density, hard sectored. I started with a controller designed for the Polymorphic machine but for double density 8 inch disk. First thing was to reduce the clock speed and change some capacitor values in the PLL circuits. I was hoping theat the formats would be similar. I next disassembled the code for the 8 inch disk. I made comments and all for the different parts, especially the sector read code. I tried the 8 inch code on the 5.25 disk. No luck there, the format was different. How different, I had no idea yet. Hard sectored disk usually use a synchronous UART to read/write data. This controller was no exception. That meant I needed to find out the sync byte used. I used my scope with delayed sweep to pick out the first data of each sector. To my surprise, it turned out to be the same as the 8 inch, the letter 'B'. Still the headers were different. I next modified the code such that after reading the sync , it would dump the rest of the data, regardless of which sector it was reading. Bingo, there was a difference. The 8 inch had track, track complement, sector, sector complement. It was the other way around for the 5.25 disk. I modified some more code but I was still getting CRC errors. Unluckily, The first sector I'd read just happend to have all zeros in the data field. I went back to reading random sectors to see what was missing in the headers. It seem that unlike the 8 inch, there were three pad bytes of zero value bytes before the data. Why they'd done this I don't know. Unlike soft sectored, one always rewrites the headers when writing data. More software modifications! Still no getting good CRCs. The headers looked good and the data read was repeatable. I added another INIR instruction to the read and found that each sector had a 0 byte and a FF byte before what looked to be the CRC. Now, this was something that made sense. A lost bit, in the data, would be hard to figure what the good CRC alignment would be. The bits would only need to be shifted to fix the trailing 0 and FF. The the CRC could be used for data recovery. Finally I could read a sector without a CRC error. Still, I wasn't done yet. Besides the different number of sectors per track ( you'll remember the work on the divide by ten ). It seems that side two is different than how the 8 inch drive did it. On the 8 inch, tracks were numbered 0 and on, the same on both sides. The sector index would first read side one and then side two before incrementing to the next track. Of coarse, the 5.25 disk were different. It numbered 0 to 34 on side 0 and 35 to 69 on side 1. This require more software changes. I'm finally able to actually read these disk. Now I can start transfering images!!Dwight _________________________________________________________________ Get in touch in an instant. Get Windows Live Messenger now. http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refres…

Hi Jim Unless someone wrote over all these disk, they should be interesting. These are archive disk from Polymorphic. I hope that they also contain the code or source for the 5.25 controller. They may have, at least, the binaries. I have to rig up my 8 inch setup as well. There are just a few 8 inch disk with the source code for the BASIC they wrote. Most of the 5.25s seem have the text for the manuals they wrote. Too bad they didn't put the graphic parts on disk as well. I've already dumped images of the SSSD disk. These had copies of the manuals as well, without the pictures. They did graphics with cut and paste then. Dental records would be a real let down. One thing I've been careful with is to remove the wire to the write gate on the disk. With all the fiddling with the software, I wanted to make sure I didn't accidentally write to the disk. It has been a long process, mainly because I've had to balance familly time with the occational hour or so of experimentation. Each time something didn't work, it'd take days to weeks before I could spend more time on the problems. I destroyed two 2716s on the project. I think I stuck them in the programmer upside down. This required another trip to the surplus shop for more spares. Every time I do significant EPROM work, I think about building a ROM emulator. Dwight _________________________________________________________________ Use video conversation to talk face-to-face with Windows Live Messenger. http://www.windowslive.com/messenger/connect_your_way.html?ocid=TXT_TAGLM_W…