how fast were drum memories?

[Paul Anderson]

The good old days...

I recall the Q-7 drums would take about 15 minutes to come to a stop when
turned off, and would power up in seven seconds or less. Surge current was
around 115 amps?

Paul

On Thu, May 10, 2018 at 3:46 PM, Mike Loewen via cctalk <
cctalk at classiccmp.org> wrote:

> On Thu, 10 May 2018, Al Kossow via cctalk wrote:
>
> On 5/10/18 10:37 AM, Al Kossow via cctalk wrote:
>>
>>>
>>>
>>> On 5/10/18 9:29 AM, Paul Koning via cctalk wrote:
>>>
>>> One that comes to mind is the DEC RS04.  It spins at roughly 3600 rpm (a
>>>> hair less, so obviously a 2 pole induction motor running off 3-phase 60 Hz
>>>> power).
>>>>
>>> Vermont Research drums (model 1175B) spun at 3450 rpm 3ph 220v, The HP
>>> 2773 on the 2000A TSB was from VR so I expect RPM
>>> would be similar for most drums of similar diameter.
>>>
>>
>> Just checked, and the LGP-30 and RPC-4000 drums are both listed as 3600
>> rpm
>>
>
>    The drums on the SAGE system (12 on each side), are listed as follows:
>
> Diameter:       10.7"
> Width:          12.5"
> Weight:         105 lbs (cylinder, only), 450 lbs for entire drum assembly
> Speed:          2914 rpm
> Heads:          Up to 12 R/W bars, with up to 40 heads on each bar, 1
> erase bar
>                 6 pairs, one for Compuuter-to-Drum (CD), one for
>                 Other-than-computer-to-Drum (OD)
>                 Head spacing 0.3" apart on each bar
> Drum Layout:    2048 registers on 33 channels (tracks), 6 fields
>                 Channel spacing is 0.050"
> Access Time:    Maximum 20ms, average 10ms
> Write Current:  110ma
>
>    The R/W bars are arranged in pairs (CD and OD) so that I/O devices can
> access the drum independently of the computer.
>
>    More than you ever wanted to know about SAGE drums (thanks, Al!):
>
> http://bitsavers.org/pdf/ibm/sage/3-42-0_Drum_System_Sep58.pdf
>
>    Here's one of the earlier style R/W heads:
>
> http://q7.neurotica.com/Oldtech/SAGE/DrumHead-1L.jpg
>
>
> Mike Loewen                             mloewen at cpumagic.scol.pa.us
> Old Technology                          http://q7.neurotica.com/Oldtech/
>