Article 4337 of alt.sys.pdp10: Path: nntp1.ba.best.com!news1.best.com!news2.best.com!feed2.news.rcn.net!rcn!newsfeed.direct.ca!look.ca!brick.direct.ca!quark.idirect.com.POSTED!not-for-mail Message-ID: <3ACF6475.45EE98FC@idirect.com> From: Jerome Fine X-Mailer: Mozilla 4.03 [en] (Win95; U) MIME-Version: 1.0 Newsgroups: alt.sys.pdp10,alt.sys.pdp11 Subject: Re: RX211 documentation References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 104 Date: Sat, 07 Apr 2001 15:03:18 -0500 NNTP-Posting-Host: 209.161.237.98 X-Complaints-To: abuse@look.ca X-Trace: quark.idirect.com 986670313 209.161.237.98 (Sat, 07 Apr 2001 15:05:13 EDT) NNTP-Posting-Date: Sat, 07 Apr 2001 15:05:13 EDT Organization: Look Communications - http://www.look.ca Xref: nntp1.ba.best.com alt.sys.pdp10:4337 alt.sys.pdp11:2135 >Bob Supnik wrote: > If anyone has scanned a copy of the RX211 (double density floppy) > manual, could you please let me know its location? TOPS-10 supported > (sort of) this device, but the peripheral handbooks are a little hazy > on the programming details, such as: > - In what order did the fill and empty commands expect to receive the > bus address and word count? > - Did the device support double sided diskettes? The manuals say no, > but the TOPS-10 driver says yes. Jerome Fine replies: I have always found that the best source for this type of information is the actual code. The RT-11 device driver for the RX02 (DY.MAC) contains a wealth of information in this regard. Even the uncommented source in V5.03 of RT-11 shows the details, but if you need anything with extra details, then contact me off list and we can probably arrange something. I would have thought that at some point, you would have paid DEC for an unlimited PDP-11 license for all and any PDP-11 software. If so, then such sources can be made available to you. Before I mention a few points, I would appreciate the courtesy of anyone who is adding to this thread to explicitly include my e-mail address in the response since the ISP I am using (LOOK.CA) has recently dropped the ball with the news server and only about 1/5 of the posts are available. The actual DEC RX02 dual floppy disk drive and the M8029 controller for the Qbus did not have hardware support for double sided diskettes. In addition, starting with V5.00 (if I remember correctly), DEC removed the extra code that was in the DY.MAC file from V4.00 that supported double sided hardware. So if you really want to see the code for a double- side floppy drive which is RX02 compatible, that is a good starting point (i.e. V4.00 DY.MAC from DEC - around 1980). Note however that the 1980 DY.MAC file probably has a bug or two in the double-sided code since I don't think DEC ever implemented an RX03. As far as I know, the M8029 probably supported an RX03 (maybe the one from that plotter company). In the digital interfaces handbook from 1980 at the very top of page 615, BIT 9 is the head select bit and can select the head to be used for double sided operation. DSD hardware uses the same bit. There are a few DECUS files available with double-sided implementations. There is double-sided hardware support available with the DSD RX03 (Data Systems Design) 3 * RL02 880/30 combination. However, DEC did not provide support for this device and I don't remember seeing any DSD version of RT-11 for the DY.MAC with double-sided software support. But I am probably having a "senior" moment and the manual is buried at this point. The reason I am positive that the DSD RX03 supports double-sided 8" floppy diskettes is that I used them for a number of years as my primary backup on the DSD 880/30 hardware. There is a version of the DYX.SYS device driver available which supports both double-sided 8" floppy diskettes along with 22 bits user addresses which can be used with the DSD 880/30. This version of the DYX.SYS operates under V5.04G of RT-11 and also allows the DEC RX02 to be used in a 22 bit environment - there is no difference between the hardware of a single-sided DEC RX02 and the DSD RX03 when used in the single sided mode - at least from the software point of view in the device driver. One point worth noting is that with an 11/73 on a lightly loaded system, the DYX.SYS device driver has enough time even with a 22 bit address user buffer to first transfer the data from/to the user buffer and then initiate the I/O transfer between the floppy media and the silo on the controller. With an 11/23, there is insufficient time to do so before the interleave is missed; thus with an 11/23 the transfer of sectors will be very slow if that procedure is followed. Also note that it is possible to put a double-pole double-throw switch into the detection circuit and convert all single-sided floppy diskettes into double-sided diskettes (at least on the DSD 880/30 with the exception of about 25% of DEC 8" floppies which I could not format in the DSD 880/30 although I never had any difficulty with any other brand of 8" diskettes). So the actual location of the index hole in the sleeve of the double-sided 8" floppy is not critical with respect to the timing. Before I learned that trick, I used a hole punch to set up the extra pair of holes in a single-sided 8" floppy. As for the order of the fill and empty commands, I don't really understand your question. I could be a smart ass and say the the usual order on a read is to first fill the silo from the user buffer, then initiate the transfer to the media which empties the silo. If you did it in the reverse order, the results would be less than desirable. But I suspect I am missing the point of the question. If I remember the software, there is a GO bit in the CSR to initiate transfers when everything is ready and set up in the CSR and other registers, so likely you may be hinting at that aspect. Since the CSR can be one 16 bit register, it is considered reasonable to set the GO bit with the same MOV instruction which sets up the other parts of the CSR in which case the address and count portions needed in other I/O page registers would have to be done first. Is that your actual question? By the way, I have not expressed my appreciation of the PDP-11 emulator which is available to the hobby user PDP-11 community along with the hobby license for V5.03 of RT-11. Sincerely yours, Jerome Fine