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Stratum Sprint Hard Drive

The Sprint is an internal hard drive for a PPC laptop. The drive itself is a 3.5" IDE type, occupying the position normally used by the second floppy drive. Its interface occupies the area of the case used by the PPC's modem, and is connected to the PPC's motherboard by means of a soldered ribbon cable.

On a PPC with a modem fitted, the interface would presumably sit behind the modem PCB.

Pictures

The hard drive interface in situ:

[Picture of the PPC innards, hard drive interface on the right]

Not covered by the cable, the interface board looks like this:

[Picture of the interface board]

BIOS

The drive interface includes a ROM, BIOS, which signs on as 'Broomsleigh Disc BIOS version 1.4.0' and includes the copyright message '(C) Copyright R.T.J.Woollett 1988,1989'. It provides the usual BIOS services on INT 0x13 and INT 0x19, allowing the PPC to access the hard drive and boot from it.

Nonstandard BIOS calls are:

--------B-131E-------------------------------
INT 13 - DISK - SET ATA AUTO STANDBY
        AH = 1Eh
	AL = standby count (0 to disable, else time in seconds / 5)
        DL = drive number (bit 7 set for hard disk)
Return: CF set on error
        CF clear if successful

--------B-131F-------------------------------
INT 13 - DISK - SEND ATA IDENTIFY COMMAND
        AH = 1Fh
        DL = drive number (bit 7 set for hard disk)
        ES:BX -> data buffer
Return: CF set on error
        CF clear if successful
           Buffer populated (all words swapped into little-endian form)

The BIOS also sets up the hard drive geometry table on INT 0x41. It supports two hard drive geometries — one with 615 cylinders, 4 heads, 17 sectors (~20Mb) and one with 980 cylinders, 5 heads, 17 sectors (~40Mb). It uses INT 0x13/AX=0x1F00 to identify the drive, and selects the 40Mb geometry if the IDENTIFY result reports 1000 or more cylinders.

The BIOS only supports one hard drive (drive 0x80).

I/O Ports

The interface appears to use the standard ATA ports at 0x1F0-0x1F7. It also accesses two other ports:

0x1F8: Read at the start of a transfer to/from disk. Possibly to initialize DMA?
0x1FA: Read at the end of a transfer to/from disk. Possibly to finalize DMA?

Literature

The following leaflet was provided with the drive:

[Sprint leaflet, front]

[Sprint leaflet, front]

Specification

The drive was also supplied with a specification document:

CAPACITY:             21.4 MB formatted
                      25.6 MB unformatted

NUMBER OF DISKS:      2
NUMBER OF HEADS:      4

NUMBER OF CYLINDERS:  614
NUMBER OF TRACKS:     1230

TRACK DENSITY:        880 TPI
RECORDING METHOD:     2.7 RLL
DATA TRANSFER RATE:   7.5 MBits/sec

AUTOPARK:             after 5 sec

SEEK TIMES:
Track to track         15 msec
Average                20 msec
Max                   120 msec

START/STOP TIMES:     5/11 sec (typical)

ROTATIONAL SPEED:     2640 rpm

POWER REQUIREMENTS:   Power-on:    5.0 W (max 7 sec)
                      Read/Write:  3.5 W
                      Wait:        1.4 W

MTBF:                 22 000 POH
MTTR:                 0.5 H

WEIGHT:               550 grams

SHOCK:
Non operating:        70 G (@11 msec)
Operating:            10 G (@11 msec)

VIBRATION:
Non operating:        5 G (5-300 Hz)
Operating:            0.5 G (5-300 Hz)

ENVIRONMENTAL DATE:
Ambient Temperature (operating):  0...+50 Degrees C
Ambient Temperature (storage):    -40...+60 Degrees C
Relative Humidity:                8...80 RH (non condensing)


John Elliott 16 October 2015