cfiaime@ihnp3.UUCP (J. Williams) (10/14/85)
Now that Tandy has announced the TRS 80/4D, is it possible to upgrade my 4P with double density / double sided drives? Installing the drives is no problem. What I am wondering about is the possibility of any changes in roms or cabling. Also, will any IBM PC compatible drive work? And, having a 4P, is this enough of a different animal from a straight 4 where I could cause problems? Thanks Jeff Williams AT&T Bell Laboratories ihnp3!cfiaime
mcmullan@unmvax.UUCP (10/20/85)
> Now that Tandy has announced the TRS 80/4D, is it possible to upgrade > my 4P with double density / double sided drives? Installing the drives > is no problem. What I am wondering about is the possibility of any > changes in roms or cabling. Also, will any IBM PC compatible drive > work? And, having a 4P, is this enough of a different animal from a > straight 4 where I could cause problems? > > Thanks > Jeff Williams > AT&T Bell Laboratories > ihnp3!cfiaime *** REPLACE THIS LINE WITH YOUR MESSAGE *** Jeff, I'm doing this posting on a 4p which runs a pair of DSDD 80T drives by Teac. They run fast; they run well. I had a bad initial experience with Tandon 80T drives (seek error after seek error after seek error....) which went away with the installation of the Teacs. The 720kB per disk (incl. boot/sys & dir/sys) is a HUGE improvement over the previous 180kB. It's faster, too, as the system views the disk as having 36 tracks/sector (both sides) and reduces the number of track steps when loading. Having to search over 80 tracks is a bit slower than over 40, but you still come out ahead. The only cabling change you need is very simple: Turn the drive cable upside down! That may seem silly, but it's necessary to make all the signals get from the controller to the drives. Big T builds the cables with certain contacts absent (side select, etc.). It seems to be a policy thing - it makes it harder to interface "foreign" equipment to "our" microcomputers. Anyway, all the lines on one side of the cable header are ground lines, and all the contacts are present. The other side has the missing contacts. If all the headers are turned over, you have all the signals present and a few ground lines floating at each end - bad engineering practice, but in my experience it hasn't made a bit of difference. If you're afflicted with hardware paranoia, you can buy new headers (at the Shack, if you prefer) and build a complete cable. On some of the 4p's, (including mine - early version) it _appears_ to be fairly easy to hack the main board to allow addressing of drives 2 and 3. I haven't done this yet, although I've heard pleasant rumors of how easy it is. Those other drives would have to be outboard, of course. The software supports this nicely. TRSDOS 6.2 format/cmd will work double sides and up to 96 tracks. You just have to tell it about in the options: the prompt for number of sides was removed by LSI at Big T's request. format :1 (sides=2,cyl=80) Try that. format/cmd will feed you the rest of the prompts. I'm pretty sure the model 4 DOSPLUS will support these and I KNOW the Montezuma Micro CP/M 2.2 does. I've had some interesting experiences with disks. You'd think that cheap disks would give you problems. Well, I got some fairly high-quality disks (BASF) rated for SSDD. About one in seven will decline formatting on its second side. (You can SEE the imperfection in the media on that side.) That's all right - they weren't rated double sided. Then I tried some cheapy disks I got for a buck apiece (including a plastic box for 10) through the NM Computer Society. Every one of 'em formatted DSDD 80T. Now, I'll grant that taking format is not the only measure of disk quality, but still - I wonder.... Duke _________________________________________________________________________ Duke McMullan (505) 255-4642 N5GAX NSS 13429R _________________________________________________________________________ 3301 Monte Vista Blvd N.E. | P.O. Box 40342 Albuquerque, NM 87106 | Albuquerque, NM 87196 _________________________________________________________________________ Dept. of Electrical and Computer Engineering University of New Mexico, Albuquerque, NM 87131 _________________________________________________________________________ {convex,ucbvax,gatech,aml-cs,csu-cs,anl-mcs}!unmvax!mcmullan {pur-ee!purdue,ucbvax!lbl-csam,philabs!cmcl2}!lanl-a!unmc!unmvax!mcmullan _________________________________________________________________________