HDDs (Was: PDP-11/45 RSTS/E boot problem

Fred Cisin cisin at xenosoft.com
Tue Feb 19 15:00:19 CST 2019

>> One of the moxt common causes of a terrible ear-piercing high whine is the
>> spindle contact.  Many old drives had a springy piece that rubbed against
>> the end of the spindle.  Over time, it would wear a divot, polish that,
>> and start to squeal.  A very light pressure on it would test that
>> hypothesis.  Not enough pressure to muffle the sound, and certaianly not
>> enough pressure to slow the spindle!  Or, pulling up on it, away from the
>> spindle.  Some people claimed that you could just rip it off.  Don't.
>> Best is to twist it very slightly sideways, so that it can start wearing a
>> new divot.

On Tue, 19 Feb 2019, Liam Proven via cctalk wrote:
> It was a 3½" EIDE drive. 8GB one, I think, but might have been
> smaller. I didn't want to open it to do that, although there was a
> time when custom PC builders "de-lidded" hard disks and fitted them
> with little acrylic windows so you could see the head move. Not sure
> I'd want to trust my data to that...

I was thinking in terms of slightly older drives than that, particularly 
Getting at the slider on newer drives wouldn't be practical.

>> Well, there don't seem to be many 350 RAMAC disks still running.
>> (I'm trying to decide what to use as a base to make a patio table out of a
>> [crashed] RAMAC 24" platter)
> Conceded.
> And thank you for the reminder that I'm not old yet.

The RAMAC came out in 1956?  The platters are 24" diameter.  Each platter 
was almost 100K!  But, with 50 platters, it maxed out at almost 5MB.
When Nikita Khruschev made a peace mission to USA, they took him on a tour 
of the RAMAC facility.  But, they wouldn't let him go to DisneyLand! (THAT 
had repercussions in the Cuban missile crisis)

> My first machine with a hard disk was my work PC in my first job: an
> IBM PC-AT, with a 20 MB FS/FH 5¼" ST-506 drive, probably a Seagate
> ST-4026. I added a second drive to the machine, a 15 MB one, and put
> Xenix/286 on it.

You could run Xenix on an XT!
The stock IBM XT HDD controller (Xebec) had physical solder pads for drive 
type, and supported 5MB, 10MB, 15MB, and 25MB drives.  The 25 was, of 
course, best (if you could get one) and would permit a 10MB DOS partition 
dual booting with 15MB Xenix.  Was that the first "dual boot" in the 
PC world?  (or was there a CP/M-86 dual boot option once they added HDD 

> A few years ago I bought a surplus 2½" 1 TB drive from a chap who'd
> bought a new notebook and put an SSD in it before use. So, 2nd hand
> but unused.
> It cost me CzK 1000, about £30 at the time.
> £30 for a terabyte. I was in a state of shock. It was so tiny, too.
> I found an online capacity comparator thing.

I used a lot of ST4096 drives.  Needed a second AT power supply for the 
second one.
> You'd need a pile of those Seagate drives the size of a _space
> shuttle_ to hold a terabyte.
> https://liam-on-linux.livejournal.com/53353.html

I use 2TB 2.5" 7.5mm Seagate/Samsung drives for MP4s of movies in 
laptops and with a Seagate GoFlex-TV (media streamer with SATA slot)
But, I finally filled 2TB 
Currently, that is the largest 7.5mm 2.5" drive available.  But SSDs are 
now available in 2TB, so when that price comes down, . . .

Heard about the NSA Utah Data Center?
That's a LottaBytes!

Grumpy Ol' Fred     		cisin at xenosoft.com

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