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ijor

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ijor last won the day on July 31 2011

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About ijor

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  1. Hi Phaeron, I'm currently on a trip. I won't be able to look into this until next weekend, in ten days or so. Please bear with me, sorry.
  2. Yep, that should work fine without doing anything special. Are you sure about that? That is not how a normal Gotek behaves. Note that when a single drive is detected the operating system will use the single drive both as A: and B: for copying purposes. But this is just a high level logical mapping performed by the OS, and should get away as long as two physical drives are detected. Also note that you must boot with both drives turned on because drive detection is performed at boot time only. You don't need to insert a disk in the second drive at boot time, but it must be connected and turned on or it won't be detected.
  3. It does, of course, both in reads and in writes. See Pokey internal schematics page 1; follow signals PreS01 and Phi2B. But even without looking at Pokey's internal design, the 6502 bus interface is synchronous. Address bus must be latched at one phase of the clock and the data bus at the other phase.
  4. I think you don't understand the point. Or might be I didn't expressed myself correctly. There is no compatibility issue here by inverting, or by not inverting, the data. We are talking about data written during format time only, not about how data is written normally with a write sector command. You could write $E5 to the disk surface, which could then read as $1A. Or you can do as this firmware does, write $1A to the disk surface that the computer reads as $E5. Either way it wouldn't be fully compatible with the 810 because the 810 "blanks" sectors at format time by writing $FF to the disk surface. So it is not that they inverted the $E5 for compatibility with the 810, because writing $1A to the disk surface doesn't make it more compatible with the 810 in anyway. My reasoning that this could be a bug, is because if you want to follow the theory I described in my previous message, then you want to write the $E5 value to the disk surface. What matter here, for this purpose, is what you write to the disk surface, not what the computer reads. So if that was indeed the purpose of writing $E5, then by writing $1A to the disks surface instead, they committed a bug. But I don't know, may be he idea of filling the sector with $E5 at format time was just to imitate what other platforms performed. Not sure that would make much sense, but who knows.
  5. Most Atari drives fill all sectors with zero when formatting the disk. That's what the 810 originally does, and most other drive follow for compatibility reasons. The actual pattern written in the disk surface is $FF because the sector data is written inverted. But technically, using $00 or $FF is not the best value to be written at format time. If you check a PC disk you will note that empty sectors are usually filled with $E5. This is because research have determined that the MFM pattern produced by writing $E5 is magnetically the most stressing pattern to the disk surface, certainly more than writing a plain $00 (or $FF). The idea is that when you format a disk, you want to test it with the "hardest" magnetic pattern. If it verifies OK when the sector is filled with $E5, then it should work with any other pattern. Or at least that is the theory. 1050 rom Rev E, at least the one Nezgar posted above, follows in some sense the concept, and fills sectors with $E5 when formatting the disk. But the strange thing is that, because the data is written inverted, the actual sector written on the disk surface is $1A, and not $E5. I guess this was a bug, let alone that the whole concept applies to MFM only, not to single density. I also assume that eventually they realized the incompatibility with the 810 and later rom revisions fill sectors with $00, writing the $FF pattern to the disk surface.
  6. In the exact example you describe, the Megafile being first in the chain, then yes, absolutely it must be turned on. And this is for the simple reason that the Megafile 60 pass through connection is actively buffered, it is not passive (as is i.e., on most Atari 8-bit SIO devices). Some signals will simply not reach the second hard disk if the Megafile is turned off. But there is no universal answer to the question as stated at the thread title. It depends on the specific host adapters. Some use a passive pass through connection, some ICD adapters are allegledly "smart" with logic that adapts depending on the other devices.
  7. Hope everything is recovered. Do you (or anyone else) have any idea about the chip photoplots? He claimed at some point he acquired a collection of photoplots for almost every single Atari custom chip. Invaluable material, hope it is not lost.
  8. Since you are using the cart code, please include the name of the one that made the port from the original Disk version. I understand it was quite some work because, IIRC, he didn't receive the original source code. He doesn't deserve the name to be removed from the title screen. Otherwise, great work. I loved this game!
  9. Would you mind taking a couple of pictures of the interface board and how the switch is connected? Should have more logic than a "simple" ST drive without a 40/80 switch.
  10. I've never seen an ST drive with a 40/80 tracks switch. Would you mind opening the drive and take some pics? I would assume it has some logic to enable or disable double step. Would be interesting to see how this is implemented. There were several 5.25 drives for the ST. I remember I.B. and Cumana.
  11. You can use replacement parts that are compatible and, apparently, they seem to be available. They have the same pinout but more resources, what Altera/Intel calls vertical migration. They would be more expensive and you would need to recompile the core to the new part, though.
  12. If you want an answer, then post a proper, polite question, instead of a so negative statement. For starters, there is no much design in the GOEX beyond the physical and mechanical adaptation. The software and firmware are generic for the Gotek, not specific for the Goex. The GOEX uses Flashfloppy firmware and, depending on the version, some HxC software. So if you have issues with the software, in first place check the Flashfloppy wiki and the HxC documentation.
  13. I was going to answer ... but the post sounds a bit like trolling to me.
  14. It is not exactly my area of expertise. But I don't know how safe is to insert the cartridge with the computer already on. I never liked that method. On the other hand, there is no alternative without custom hardware, or at least custom OS.
  15. Honestly, no I didn't note until now that you mentioned it. But, unfortunately, I don't think this is very common for most other publishers. May be Antic did it in purpose to support the Chinon mechanism that appeared in later XF551 units. Without a second index hole, those drives can't access the flippy side at all.
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