Johnny Billquist wrote: > Not that I care what Holm Tiffe smokes, but I can at least comment what > you write, Tony. :-) > > On 2015-09-21 16:02, tony duell wrote: > > > >[Russian PDP11-a-like] > > All bets are off when we talk about clones, since they might be rather > different in details... > > >>I've tried to boot an RX01 Floppy in RX02 mode, that failed on all disks > >>I've tried. Is an original RX02 able to boot (RT11) from an RX01 disk? > > > >As far as I know, it can't. An RX02 can read/write an RX01 disk, but the > >software > >interface to the controller is so different (the RX)2 uses DMA, the RX01 > >doesn't for > >one thing) that the RX02 cannot boot an RX01 disk.
Hmm.. I don't know if the Controller board (Inside the Computer) would be "RX02-able" when I read this. Just FYI: http://www.tiffe.de/Robotron/PDP-VAX/E60/E60-06.jpg That's the I4 Controller board that is connected with a flat cable to the Drive..working as RX01 at least.. And that is the Controller Board in the Drive itself, the red cable goes tro the I4 Board in The computer: http://www.tiffe.de/Robotron/PDP-VAX/E60/disk-proz.jpg ..and if I look at this picuture it looks more that it contains AM2909 sequencers instead of an AM2910.. > > Of course an RX02 *drive* can read an RX01 *floppy*. And yes, a system > with an RX211 and an RX02 *drive* can boot from a floppy that what > written by an RX01 *drive*. But you need the boot code for an RX211 > controller, and that boot code also needs to handle RX01 format > floppies. If the boot sector on the floppy is for an RX11, then no, an > RX211 will not understand things. The programming model for the two > controllers are different. You need different device drivers. > > But this is really a question about the controller and the software > running it, not the floppy or the drive. > > >>I know that a different device driver has to be used normally, but I had > >>no RX02 media and wasn't able to make one, since the machine has no other > >>drives connected and the card cage is mechanically not compatible (metric > >>dimensions including the fingers). > >>I know that in the RX02 Mode the Drive has an format track command that > >>doesn't exist in RX01 mode, that's documented. How about the RX02? > > > >The RX02 has a 'set density' command that can be used to reformat a > >formatted single density disk as double density. > > Yes. And it's just flipping a bit in the sector header. And the drive > changes between the densities for the data part of each sector. So you > can actually have different densities on a per-sector basis with an RX02 > drive. > > >>Is there somewhere a picture from the Conteroller PCB of the DEC RX02 > >>(just to look at). The russian controller has a 2910 and four 2901 if > >>I remember correctly... (K1804VU1 and 4xK1804VS1) > > > >The RX02 drive contains a couple of 2901s and a few of the sequencer chips > >(I think 2911s, maybe 2909s). I've seen a 3rd party Qbus card that > >connected to > >normal Shugart drives and which could red/write RX02 disks, I think that > >had > >a couple of 2901s and a 2910 on it. > > What people need to understand is that there are a bunch of controllers > and combinations. If we just contain our self to Unibus controllers, we > have two. The RX11 and RX211. The RX11 works with both the RX01 and > RX02. However, an RX02 needs to be set in an RX01-compatible mode if > used with an RX11 (a couple of dip-switches in the drive). And that also > turns it into essentially an RX01 (can't deal with double density within > the RX11 interface). The interface to an RX01 is different than the > interface to an RX02, even though they use the same flat cable. Ok, got it. But I know that this russian drive has the described Jumper for switching between RX01 and RX02, but I don't know what this requires as Controller in the computer... > > The RX211 can be used with both an RX01 and an RX02, as far as I can > remember. But that implies that there would need to be some switch or > jumper on the RX211 in order to interface it with an RX01 (or some > automatic detection), and I can't remember seeing that. But it might > just be my memory failing me. > But the RX211 works differently than the RX11, so from a program point > of view, they are totally different. > > The RX02 drive, then, in turn, can read and write both RX01 and RX02 > floppies. No special tricks are required. The drive will detect, for > each sector, which format it is in, and will switch mode accordingly, > and return the right about of data (RX02 sectors holds 256 bytes, while > RX01 sectors holds 128 bytes). The software can thus also easily see > what type of floppy it is reading. > RX211 device drivers obviously then can handle both RX01 and RX02 > floppies, when used with an RX02 drive. And from the software point of > view, the sectors just contains different amount of data. > > Johnny Regards, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Freiberger Straße 42, 09600 Oberschöna, USt-Id: DE253710583 www.tsht.de, i...@tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741
