Paul.Birkel@K.GP.CS.CMU.EDU (03/14/88)
My apologies if this problem has been addressed in the past 6 or so months that I've been off the INFO-CPM list. I'm considering the purchase of a used Micromint SB180 configured with a pair of DSDD 96tpi 5 1/4" drives. It's running a custom ZCPR3 from ECHELON. Boots and runs fine off of a set of 96tpi disks. The problem is that it can not read a disk formatted at 48tpi! This includes the original distribution disks, and disks it has just formatted to 48tpi using the FVC (format, verify, copy) utility. The same problem occurs when trying to read a disk in KAYPRO II format (SSDD 48tpi), or using FVC to format such a disk. FVC is perfectly happy in 96 tpi "mode". In all such cases, I get a bad sector error, usually on track 1 sector 01 or something like 20. Booting from the distribution disks gives me the system header message (like "ZCRP3 56k, etc") and then hangs. I do not know if the ROM is producing this or not, but I would guess that it *is* reading track 0 correctly since it is determining the system "size" correctly. On the other hand, under some non-boot circumstances it fails on track 0 as well, so I'm not sure about this. I thought that the problem may be that the system is trying to read the disks in 96tpi mode, except that FVC when attempting to verify a disk formatted on a KAYPRO II does produce a header correctly identifying the format, therefore *must* be accessing the appropriate tracks. Just in case I changed the step rate from 10 to both 6 and 20 ms. with no effect (except more noise in the later case!!). I don't know of any other setable system parameters that might affect this problem. One could argue that the drive speeds have drifted leading to problems with the distribution disks, but that does not explain identical behavior on either drive, and the failure of FVC (which formats without complaint the appropriate number of tracks and sides) to happily verify even a floppy it has just formatted. One could argue that it's a write problem (on formatting), except the distribution disks should be readable. If it were bit rot in the device driver then I wouldn't expect *both* of two 96tpi system disks to exhibit the same behavior. The drives, I believe, are standard 55Bs (?). I have no documentation on them. The SB180 docs describe jumpers which basically control things like head load, motor control, and panel lights. The only board jumper has to do with 8" vs. 5 1/4". So I don't think that there is a hradware configuration problem. As much as I otherwise like the system, I'm not purchasing it 'til I can exchange data with it!! Unfortunately, the original owner died 3 years ago and his brother is only now trying to sell it after gathering dust for the duration. The brother is not especially technically knowledgable and just wants to move it. I'm at a loss as to where the problem might lie. Help? paul birkel Dept. of Computer Science Carnegie-Mellon University Pittsburgh, PA. 15213 pab@k.cs.cmu.edu (412) 268-8893
David_Michael_McCord@cup.portal.com (03/15/88)
The Sb180 electronics and software make it virtually impossible to read or write 48tpi disks in a 96tpi drive. However, an inexepensive solution is to add a 48tpi drive to the system, and then you can read and write 48tpi formats to your heart's content, including mushdos if you buy the UNIFORM product from Micromint. I have an SB180 configured with 2 96tpi drives as A: and B:, and a 48tpi drive as C:. Works great.