Mac Plus SCSI Hard Drive Issues

Hi nosoupforyou,

I would remove one of the system folders off the drive, it could cause some boot confusion. And also use your sys 6 disk to do a disk first aid on it.

cheers

patrick

There was an obscure problem with the reset sequence in the Mac Plus and a drive feature called "Unit Attention". If the Hard Drive in the enclosure has a jumper setting for it, you want to place a jumper on the pins for "Disable Unit Attention".

All of this is predicated on your using a good, shielded cable made for SCSI drives (not just any old RS-232 cable) and having a terminator on the second port on the Hard Drive Enclosure.

SS is the Self-Seek (self Diagnostic) strap. do not use it
EP I don't know, but I guess it means supplies External Power to the Bus
WS Wait Spin, drive delays initial spin-up until commanded
A2, A1, A0 are Address jumpers

Check the drive for terminating resistor-packs on the circuit card next to the ribbon cable connector, it may be double terminated. Best practice for an external drive is to remove the resistor packs and use the external terminator.

nosoupforyou
The Quantum ProDrive ELS was a common model in the middle to late models of the Classic AIO series. It was found in the Mac II, SE/30 and Classic II for sure, and probably in the Colour Classic, in 40-160MB sizes. You have jumpered yours for 0-4-0 by jumpering A2. However, they were being used in virtually sealed enclosures (since Apple did not encourage users to go inside), and were usually not jumpered at all. Termination was onboard, and not easily removed by a user, and the ID pins were left unjumpered as the 'conventional' 0-0-0. You can leave the other pin pairs unjumpered. These drives were supplied when interleave factors had reached 1:1, ie all information was read from a cylinder directly in a single revolution to transfer through a SCSI port at up to 1250kB/s.

Your Plus, as the first of the first to have a SCSI port as standard (although the 512Ke's ROM was SCSI-savvy, ready for add-on cards and ports), had an interleave of 1:3, ie it took three revolutions of a cylinder to read all the data, as only every third sector was read in each revolution, so that the Plus did not choke on its own data stream at a screaming 312kB/s, compared with the SE FDHD's 1:2 ratio and 656kB/s. These interleaves resulted in logically continuous sectors of data that were not physically contiguous.

Drives could be set to one interleave ratio at a time with a drive utility, either fixed (Apple) or configurable (eg Silverlining 5.8.x). At the moment, you probably do not know what interleave was set for your external drive, or with which utility. The HDD itself is not contemporary with early Pluses, and could even be trying to send data from a 1:1 interleave through a hopelessly outclassed SCSI port on the Plus. Your best hope of making progress is with a copy of Silverlining, which is much more informative than HD SC Setup and which can replace the Apple driver (if need be) to regain control, but most of all simply for its diagnostic output.

It is conceivable that later Pluses had faster SCSI and used an interleave of 1:1, but a utility that confirmed the case would be useful indeed. The link for Silverlining 5.6.3 on Gamba's site is defective, defaulting to something not very useful. There are other possibilities, including a patched version of HD SC Setup, which recognizes most drives. You may do better on a driver archive site. Silverlining 5.7 can also be updated with the updater from Gamba.


Apple IIe; 68K: 11DT + 4PB; PPC: 5DT + 3PB; G3: 6DT System 6.0.8 to OS 10.4.x

Denis-

You are quite correct that a 3:1 interleave is optimum for a Mac Plus. Finding a utility to format with that interleave may indeed be difficult. The drive "just misses" being able to read/write the next-numbered sector and must endure nearly another full rotation until the correct sector comes under the heads again.

The wrong interleave is known to produce slowness, but not the crashes and non-performance seen here. Do you think this could be caused by double termination (resistor packs on the drive in addition to the external terminator)? Do you have another theory?

Grant
Speculating from a distance is always fraught with the risk of getting egg on the face, but the first suspect is that raised by Patrick: the presence of two System Folders on an unpartitioned drive.

The second suspect is yours, the matter of termination, with the proviso that ELS ProDrives do not have the extra jumper pairs SS, EP, and WS, nor accessible resistor packs that LPS drives do. Most ProDrives that I see are of the ELS kind. Perpetual seek activity without a resolution smells of strangulation by data, or starvation for data, but there could easily be other causes. Termination within the bus instead of only at the ends might be a greater problem than double termination at one end, or than lack/failure of termination (as opposed to termination power) within the Plus. Thus, the reported sensitivity to change of external terminator position on the external drive housing is puzzling, unless the housing's internal cabling is defective. Are the resistor packs of NSFY's LPS drive there or not there at the moment? Is the Plus supplying termination power, and should the drive be jumpered to use it?

How often have I thought that the problems reported by OPs could be quickly nailed if only we were beside the posters with our own equipment ... (Duh!) because seeing can be so much more revelatory than reading. Right now, another, known-good external drive would be of inestimable value to NSFY to help to distinguish what is failing. Failing that, I cannot too strongly suggest that a utility of the Silverlining kind is needed.


Apple IIe; 68K: 11DT + 4PB; PPC: 5DT + 3PB; G3: 6DT System 6.0.8 to OS 10.4.x

nosoupforyou,

I am with Patrick on this one. The Plus hated multiple system folders. It would sometimes boot from 6 with another 6 onboard but 6 and 7 on the same partition or drive will send it into cardiac arrest. It was common to find a system folder on a game disk. Copying an entire game disk to your hard drive would soon result in multiple system folders on the hard drive and sure disaster. Blessing a system folder came much later.

The fact that everything works fine after the first system folder has been found on the floppy disk means that the hardware is just fine. There is nothing unusual about your problem or cure. You could backup your data, partition the drive and then designate the startup drive/partition to alternate between the systems as you need them.

This is not far removed from the days of having to reboot the machine for every software title. Remember those days?

Jim