My First Disk Drive

I see I remembered some details wrong, including the number of platters (it’s 6, not 5).

Quoting the IBM article:

The IBM 1311 Disk Storage Drive provided storage for 2 million characters. Developers of the 1311 engineered twice the recording density of the IBM 1301 Disk Storage Unit by reducing the space between the head and the disk by about a factor of two.

The 1311 used the IBM Disk Pack (later designated the IBM 1316 ), an interchangeable package containing six 14-inch-diameter disks in a four-inch stack, weighing 10 pounds (seen above in the man’s left hand). Each disk surface contained 20 pie-shaped regions. Sectors were segments of track lying within a region, and were the smallest addressable unit, with a capacity of 100 characters. Average access time to any sector was 250 milliseconds, which could be reduced to 150 milliseconds with an optional direct-seek feature. The disks were rotated at 1500 rpm, tracks (50 to the inch) were recorded at up to 1025 bits per inch, and the usual head-to-surface spacing was 125 microinches. The ten recording surfaces provided in normal usage a storage capacity of 2 million characters, the equivalent of approximately 25,000 punched cards or a fifth of a reel of magnetic tape.

We had the “direct-seek” feature, which as I remember it meant the heads didn’t return to the outer edge before starting the next seek.  Note those units—some of you are perhaps old enough to remember milliseconds!

Only 1,500 RPM.  It’s gradually gone up, so that enterprise high-performance rotating disks today are 15,000 RPM (but lots of people needing that kind of performance are using SSDs instead).

As I recall the 1401 didn’t use the fixed sectoring; or maybe what we used was layered on top of that or something. It’s been a while now. My memories aren’t precise, but we read records considerably bigger than 100 characters as a single operation, and didn’t have to specify the size on each read (I think it was formatted into the pack somehow).

IBM archives article


Found the missing birthday presents, so I get to compare the Dundee and the Chivers ginger marmalade head-to-head.  The Dundee was what we used for decades, before we stopped keeping such things around (stopped doing biscuit breakfasts, I guess).

Several marmalades
Several marmalades

The Chivers is a bit lighter in shade and seems to have less solid ginger in it. The flavor is rounder and mellower, and has essentially no trace of “sharp” to it.

The Dundee is not as good as I remember it being. Memory of flavors over decades are not reliable, and people mostly lose taste sensitivity as they get older, so this doesn’t really prove a change in the marmalade, however. Still, I prefer it to the Chivers.  Unfortunately it seems to be hard to get; Lydy had to buy a batch of six jars to get it from Amazon (so it’s a good thing I still like it).

(Incidentally, I’ve now received well over a dozen jars of preserves from Amazon in many separate orders, not not one single jar got broken. I’m sure some do, but it appears to be pretty rare.)

One reason I’m buying these things from Amazon is that it’s much harder to find them in stores locally than it used to be, both regular grocery stores and specialty shops.

(The Frank Cooper vintage orange is present because it was one of the missing birthday presents that was finally turned up.)