The DF32 Disk File an Control is a fixed head hard drive with a total capacity of 32K 12 bit words. It can have up to 3 DS32 Extender Disks slaved off of it for a total system capacity of 131,072 words. This was normally used with the earlier machines, the PDP-8, PDP-8/S, or PDP-8/I. All the units I have are made with the older R series logic which is a diode transistor logic (DTL) made with discrete diodes and transistors. The later units were made with the standard TTL IC M series logic for use with positive bus PDP-8/I's.
The DF32 was attached to the computer through the 3-cycle data break interface via 11 to 13 cables. The 3-cycle data break was a type of direct memory acess (DMA). The processor wrote to various registers in the DF32 to setup the transfer then the unit transfered the data while the processor was able to do other things. The 3-cycle was because the transfer was 3 operations with the DMA address and word count stored in the processors memory. This was done to have less logic on the peripherals.
The drive hardware did not organize the disk into fixed size sectors, each word on the disk was capable of being read or written independently with a maximum of 4096 words in one transfer.
|Data Transfer Rate||66 microsecond per word|
|Average Access Time||16.67 millisecond|
|Words per track||2048|
|Recording Media||Nickel-cobalt plated disk 10"x1/4"|
|Operating Environment||Maximum: 32 to 130 F
Recommended: 70 to 85 F
Relative Humidity: 20 to 80 %
|Heat Dissipation||500 Watts|
The DF32A/DS32A which operated off of 50 Hz power rotated slower so data transfer was 80 microseconds and average access time was 20 milliseconds. Since the heads land on the disk when the power is removed it was recommended to not power down the drive motor any more than absolutely necessary.
I haven't gotten to scanning in documentation for this unit or making the PDP-8/I I have it attached to available. One of these days... If you want more on this unit ask and I can try to make it available sooner.
Documents related to DF32 and DS32
The following picture links below also have descriptions of what is show in the pictures.
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Front view ( 66K) Back view ( 62K) right view ( 42K) left view ( 43K) bottom view ( 36K)
Disk platter ( 49K) Disk cover ( 44K)
Card area ( 58K) Card area cables unplugged ( 54K)
Closeup of wirewrap backplane ( 85K) Top view of cards ( 63K)
Heads ( 49K) Head top closeup ( 50K) Head front closeup ( 31K)
Black flat coax external bus cable ( 37K) Shielded Mylar external bus cable ( 26K)
|2||G083 Disc Preamplifier|
|1||G284 Disc Writer|
|1||G285 Series Switch||Part of head select|
|2||G286 Center Tap Selector||Part of head select|
|2||R002 Diode Network|
|3||R111 Expandable NAND/NOR gate|
|4||R113 NAND/NOR Gate|
|5||R123 Input Bus Gate|
|5||R202 Dual Flip Flop|
|5||R203 Triple Flip Flop|
|15||R205 Dual Flip Flop||Disk address and data registers|
|2||R302 Dual Delay (One Shot)|
|1||R303 Integrating One Shot||Start of track detection|
|3||R602 Dual Pulse Amplifier|
|3||R603 Triple Pulse Amplifier|
|1||W005 Clamped Load|
|1||W023A||Head data cable|
|1||W033A||Head select cable|
|4||W103 PDP-8 Device Selector|
|2||W532 Dual AC-Coupled Difference Amplifiers|
|2||W533 Dual Rectifying Slicer||Convert head output to digital signal|
|2||W990 Bare Board|