IN-103 Setting Densities for Magnetic Tapes in RT11 Liz Quigg and Peter Heinicke Dec. 6, 1983 Abstract ________ Information on setting the densities properly for the STC, AVIV, TJU16, and TU10 under RT11 is given. Systems Supported: RT-11 Setting Densities for Magnetic Tapes in RT11 Page 2 1.0 INTRODUCTION There are four possible magnetic tape systems interfaced to the PDP-11: the TU10 tape unit with TM11 Controller, TJU16 tape unit and controller, STC tape unit and controller, and STC tape unit with AVIV controller. These will be referred to as TU10, TJU16, STC, and AVIV, respectively. RT11 has four handlers to use with magnetic tapes: MM, MJ (non-file oriented version of MM), MT, and MH (non-file oriented version of MT). The following charts show which handlers should be used for which tape systems and the density settings used in the SET command to achieve the desired densities. In RT11 the "SET" command actually changes the SYS file on the disk for the handler. The last "SET" command for the density will control the density used when the handler is used, even if the system is rebooted. Hence to be sure that you have the density that you want, you are better off using the SET command before using the handler. The only way that you can establish the current setting in the handler is to run PATCH and look at the location of the density setting and interpret the contents using the charts that follow. This is only recommended if you need to know the density of tape that you have just written and have not changed the setting after writing it.The addresses to look at with PATCH are for RT11V4B. They may not be valid for RT11V5. It is also wise to unload the handler before setting the density to assure that you get the density that you want. If the handler is already loaded, you will only change the .SYS file and the handler in core will keep the setting that it had when you loaded the .SYS file. The UNLOAD and SET can be done in the startup file so that you set the density to a default that you like everytime you reboot. Unless you include the UNLOAD and SET commands in your startup file, then the density setting on rebooting will be the last setting that made regardless of when you used the system last. This is true for all magnetic tape systems. The STC and AVIV do have the ability to read either 1600 or 6250 BPI tapes, no matter what you set the density to. The TU10 and TJU16 require the proper density setting to read a tape. The charts follow: Setting Densities for Magnetic Tapes in RT11 Page 3 STC (with STC controller, not AVIV) ___ _____ ___ ___________ ___ ____ Possible Densities 1600 and 6250 BPI ________ _________ Internal Name in RT11 MM (file oriented) and MJ (non-file oriented, for ________ ____ __ ____ MULTI) To get 1600 BPI __ ___ ____ ___ UNLOAD MM (for file oriented) or UNLOAD MJ (for non-file oriented) SET MM: DENSE=1600 (or 800) for file-oriented or SET MJ: DENSE=1600 (or 800) for non-file oriented To get 6250 BPI __ ___ ____ ___ UNLOAD MM: (file oriented) or UNLOAD MJ: (non-file oriented) SET MM: DENSE=6250 (file oriented) or SET MJ: DENSE=6250 (non-file oriented) Default on Reboot _______ __ ______ Default density setting on reboot depends on the last SET command used. The setting is written into the .SYS file on the disk and does not affect setting of handler if it is already "LOADED" in core. Method to Determine Current Density Setting in Handler for RT11V4 _ .R PATCH *MM.SYS (file oriented) *1050/1700 Set to 800 BPI results in 1600 BPI on STC 2300 set to 1600 BPI results in 1600 BPI on STC 3700 set to 6250 BPI results in 6250 BPI on STC or *MJ.SYS (non-file oriented) *1044/1700, etc. interpret the same as above Setting Densities for Magnetic Tapes in RT11 Page 4 AVIV (with AVIV controller with STC tape unit) ____ _____ ____ __________ ____ ___ ____ _____ Possible Densities 1600 and 6250 BPI ________ _________ Internal Name in RT11 MT (file oriented) and MH (non-file oriented) To ________ ____ __ ____ __ get 1600 BPI ___ ____ ___ UNLOAD MT: (file oriented) or UNLOAD MH: (non-file oriented) SET MT: DENSE=200 (file oriented) or SET MH: DENSE=200 (non-file oriented) To get 6250 BPI __ ___ ____ ___ UNLOAD MT: (file oriented) or UNLOAD MH: (non-file oriented) SET MT: DENSE=800 (or 556) (file oriented) or SET MH: DENSE=800 (or 556) (non-file oriented) Setting DENSE=800 is preferred since it leaves the density set to the standard expected for the TU10 (also controlled with the MT handler). Default Density on Reboot _______ _______ __ ______ Default density setting on reboot depends on the last SET command used. The setting is written into the .SYS file on the disk and does not affect setting of handler if it is already "LOADED" in core. Method to Determine Current Density Setting in Handler for RT11V4 ______ __ _________ _______ _______ _______ __ _______ ___ ______ .R PATCH *MT.SYS or MH.SYS *1036/60000 Set for 800 BPI results in 6250 BPI on AVIV 20000 556 BPI " 6250 " 40000 807 BPI " 1600 " 0 200 BPI " 1600 " Setting Densities for Magnetic Tapes in RT11 Page 5 TJU16 _____ Possible Densities 800 and 1600 BPI ________ _________ Internal Name in RT11 MM (file oriented) or MJ (non-file oriented) ________ ____ __ ____ To get 800 BPI __ ___ ___ ___ UNLOAD MM: (file oriented) or UNLOAD MJ: (non-file oriented) SET MM: DENSE=800 (file oriented) or SET MJ: DENSE=800 (non-file oriented) To get 1600 BPI __ ___ ____ ___ UNLOAD MM (file oriented) or UNLOAD MJ (non-file oriented) SET MM: DENSE=1600 (file oriented) or SET MJ: DENSE=1600 (non-file oriented) Default Density on Reboot _______ _______ __ ______ Default density setting on reboot depends on the last SET command used. The setting is written into the .SYS file on the disk and does not affect setting of handler if it is already "LOADED" in core. Method to Determine Current Density Setting in Handler for RT11V4 ______ __ _________ _______ _______ _______ __ _______ ___ ______ .R PATCH *MM.SYS (file oriented) *1050/1700 SET to 800 BPI Results in 800 BPI 2300 " 1600 BPI " 1600 BPI 3700 " 6250 BPI " 1600 BPI or *MJ.SYS (non-file oriented) *1044/1700, etc. interpret the same as above Setting Densities for Magnetic Tapes in RT11 Page 6 TU10 ____ Possible Densities 800 BPI (9 track) and 200 (7 track), 556 (7 track), ________ _________ and 800 (7 track) Only 800 BPI (9 track) used at FERMILAB Internal Name in RT11 MT (file oriented) or MH (non-file oriented) ________ ____ __ ____ To get 800 BPI __ ___ ___ ___ UNLOAD MT (file oriented) or UNLOAD MH (non-file oriented) SET MT: DENSE=800 (file oriented) or SET MH: DENSE=800 (non-file oriented) If the last setting for the handlers was 200, 556, or 807 because the AVIV was being used, it causes trouble when you try to read the TU10. You should SET density to 800 to be sure if you also use the AVIV on your system. Default Density on Reboot _______ _______ __ ______ Default density setting on reboot depends on the last SET command used. The setting is written into the .SYS file on the disk and does not affect setting of handler if it is already "LOADED" in core. Method to Determine Current Density Setting in Handler for RT11V4 ______ __ _________ _______ _______ _______ __ _______ ___ ______ .R PATCH *MT.SYS (file oriented) or MH.SYS (non-file oriented) *1036/60000 Set for 800 BPI /40000 Set for 556 BPI /20000 Set for 807 BPI /0 Set for 200 BPI Setting Densities for Magnetic Tapes in RT11 Page 7 Determining the Density of a Tape in RT11 Sometimes you have a tape for which you do not know the density. Some advice follows on how to determine it's density. STC's have the ability to read 1600 or 6250 BPI tapes no matter how you have set the density. Hence the STC is not a particularily useful device to distinguish between densities except if you try to read an 800 BPI tape. In the latter case, you will get an error. You can use the TJU16 to distinguish between 800 and 1600, and possibly 6250. You will get an error if you try to read with the wrong density on the TJU16. If you assume that this error is caused by density only, (i.e., not a skew problem or actual hardware read error), then you can rule out the failed density for that tape. The TU10 reads only 800 BPI for 9 track tapes or 200, 556, or 800 for 7 track tapes (the latter three not usually used at Fermilab). If you try to read a 1600 BPI tape on a TU10, you get an error.