sschneider@pro-exchange.cts.com (The RainForest BBS) (12/24/89)
====================================== | CMS-S20/A2S Conversion to an SD-60 | |------------------------------------| | Squeezing those extra bytes from a | | CMS interface card and other notes | ====================================== With special thanks to all those that went before me ; Dr. Ken Buchholz, Rick Hannon, Paladin, Tim Grims and John Thomas........ (C)1989 by Steve Schneider ----------------------------------------------------------------------------- There's been quite a bit written on upgrading the size of one's SCSI drive or repairing one that's gone bad or even homebrewing one from scratch so I won't repeat all of the good stuff that others have written concerning same... Just wanted to add a couple of hints, notes and words of encouragement. #1) A ST277N-1 Seagate drive can be found now for the same price as the old 65 megabyte 40 msec ST277N... around $449. I found prices on this drive ranging from $391 to $550 and chose to go with the quality, service and dependability of HardDRIVES International. (1-800-234-DISK) I added the $29 2nd Day Air option and had the new 65 megabyte 28 msec ST277N-1 in my hot little hands about 42 hours after I ordered it. Not paying sales tax made up for the shipping premium. #2) The ST277N-1 has a green I/O LED mounted on the drive SCSI PWB. While I have worked in electronics for 30 years I couldn't bring myself to tak- ing a soldering iron to the PWB to remove the LED to add the old jumper wire set for the green read/write light mounted on the CMS's case. If I did that I would automatically VOID the warranty on the drive and if it wound up bad I'd be out $478. <shudder> So I did the next best thing. I took the CMS case (with the drive removed, of course) and positioned it securely on a flat surface with the power supply PWB masked off with a bit of paper and tape. I preceded to drill a 5/8 inch hole in the front of the case (a smaller pilot hole drilled first makes this a breeze) to match where the SCSI PWB green LED would shine through when I installed the drive mechanism. After drilling the hole make certain all the small pieces of filings and metal dust are blown out of the case and then you can remove the protective paper and tape from the power supply PWB. Now you can install the drive per instructions of those who've gone before. #3) EXTRA BYTES!! If you are using a CMS interface you are cheated out of the two 32 megabyte volumes that ProDOS would allow. *BUT*, you can get some of it back using this little trick. When you set up the jumpers on the CMS interface card you don't have much choice in the size of volume one. It can only be 30 (there isn't a 32) megs. So PS1 would have no jumpers, starting point 0, and PS2 would have a jumper on pin set 4, to indicate a starting point of 30. However, by setting the SZ1 jumpers to 1-3-4-5 (30 meg SIZE matches the starting and ending boundaries of PS1) and then setting SZ2 jumpers to 1-2-3-4-5 (32 meg SIZE allowed here be- cause you having no ending boundary other than SIZE) you have at least been able to get 62 megs from the 65 meg drive. A word of caution here for those of you that have already set both volumes to 30 and now want to change the jumpers on your card and go back in to reformat only the second volume. Even though the CMS utilities *SEEM* to indicate that it is possible to format only one volume of a two volume drive if you try to do it to volume two it will actually reformat both volumes. So do it the right way; back up both volumes to disk, reformat and then restore. Do *NOT* use an IMAGE backup system for this for OBVIOUS reasons. I use BACKUP.SYSTEM from Apple Computer for this kind of procedure. #4) The weird noise you hear for a few seconds every ten minutes or so with drive powered on is the drive re-sync'ing itself and nothing to concern yourself about. #5) With the ST277N-1 installed and with the 11/09/87 ROM upgrade installed on the CMS interface card and the card in slot #7 this drive will auto- boot the system if all power is turned on at the same time (Some of the earlier CMS drives required the drive to be up to speed before the com- puter was powered up.) Another feature of the ST277N-1 is the heads are "self-parking" at drive power down. (I can only verify the auto-boot on my Apple//e.... there may be differences with the IIgs) #6) If you are replacing a defective ST225N (65 msec average access time) with the ST277N-1 (28 msec average access time) you will notice a quite obvious decrease in disk I/O times even though you are limited by hard- ware (Apple CPU, et al) from enjoying the 28 msec access. 38-42 msec is more along the actually obtained average access speed. +===========================================================================+ | UUCP: crash!pro-exchange!sschneider COMPU$ERVE : 75166,2544 | | ARPA: crash!pro-exchange!sschneider@nosc.mil GENIE : sschneider | | INET: sschneider@pro-exchange.cts.com APLINK.PE : <shrug> | +---------------------------------------------------------------------------+ | The RainForest @ 305-434-4927 / PO Box 841422, Pembroke Pines, Fl, 33084 | +===========================================================================+