Adding a Winchester to your System
Some 18 months ago I was being given a guided tour by a fellow Nascom-Nut of his
system, and its last addition “the Winchester”. Whilst studying the thing enviously,
I asked where he obtained the finance. Bank Robbery? Pools win? Rich aunt died?
No! He insisted it’s much cheaper than you imagine. It is indeed, and not as difficult
to install as you might think.
“but they’re costly”
A look through the Gemini price list reveals that you would need to lash-out
something like £1000, but using second-hand components it can be done for perhaps
a fifth of that price. This is about the same as you might pay for a good size
“I don’t mind changing disks”
So what are the advantages that a winnie gives you? The answer can be broken down
into two things, speed of access to your files and a large amount of storage. The two
things are of course interlinked, but let’s look at speed first.
With a normal floppy drive, data is transferred to your system at the rate of 256
Kbits/sec (500 Kbps for 8″ drives), with a winnie using the SASI/ST506 interface the
rate of transfer is 5 Mbits/sec, over 20 times faster than a floppy drive. The step up
to a winchester system from floppies is like stepping up from Cassettes to floppies.
In addition although the stepping rate of most winchester’ s is nominally 3mS, most
modern microprocessor controlled winnie’s can accept step pulses much faster than
this (known as ‘Buffered Seek’) in some cases separated by as little as 16uS, these
are buffered by the on-board micro and the stepper motor is-driven faster, until it
gets close to its destination where-upon it switches back to 3mS for the last few steps.
However it must be admitted that this much higher rate of stepping can be somewhat
offset, since most winchesters have considerably more cylinders to step over than
even an 80 track disk.
Perhaps the biggest boon to having a winnie based system, is the large amount of
storage which can be accessed (at high speed). Even a small winnie with perhaps
5Mb can hold many (all?) of your programs and data, so avoiding the need. to swap