> First, is the speed increased with two processors of the same make
> and, specs.

  Intel recommends that multiple processors in the same motherboard
be within one "step" revision of each other.  Wider differences may
or may not work; certainly both must be of the same processor type
and will be run at the same speed.

> Second, if I installed two identical say--700mhz processors would I
> get 1.4ghz speed or just 700mhz speed.

  You will get 700 MHz speed.  But IF you are running an OS[*] that
enables the second CPU and schedules some tasks to run on it, you'll
get about the same *overall* throughput as a 1 GHz or so single CPU.
No single execution thread will run faster than 700 MHz, but you'll
often be able to have more than one running at the same moment.

[*] Windows NT/2K/XP, or any Linux or *nix flavour, or BeOs....  NOT
Win 95/98/ME (or 1.x-3.x) or DOS or OS/2....
  Note also that not all CPUs are multi-CPU capable.  AMD has
recently reintroduced this feature, after dropping it for a while,
and Intel doesn't officially support it on Celerons or P4s (except
the P4 Xeon), but on some models the necessary circuitry is present
and can be re-enabled.

> Third, if the latter is correct, how does this increase the speed
> according to the advertising.

  It's sort of correct, but not complete.  See my answer to "Second"
above.

> Fourth, would I need a larger power supply to support two
> processors.

  Not significantly.  Hard drives and fans (mechanical motors)
probably consume the largest proportion of power.  External signals --
 serial, parallel, video, network, and so on, the next.  Purely
integrated circuits are fairly low on the list -- a CPU, which is a
honkin' big chip, is typically less than 10 watts.
  Each CPU needs circuitry to step down the power supply voltage from
3.3 or 5 volts to the <2 volts used by current CPUs.  Some dual-
capable motherboards are sold without this VRM (Voltage Regulator
Module) for the second CPU, and so in that case there would be an
extra cost to upgrade later.  But the VRM is not the power supply.

> I would appreciate any input from somebody who knows the ins and
> outs of using dual processors.  Thanks  Ed

  My main desktop is a dual-CPU unit, and I've installed and worked
with a couple of hundred dual- and quad-CPU servers.


On 13 Dec 2001, at 12:28, Edwin Bogert wrote:

> I'm inquiring about the advantages or, dis-advantages of various
> dual socket mobos available. First, is the speed increased with
> two processors of the same make and, specs.  Second, if I
> installed two identical say--700mhz processors would I get 1.4ghz
> speed or just 700mhz speed. Third, if the latter is correct, how
> does this increase the speed according to the advertising. Fourth,
> would I need a larger power supply to support two processors. I
> would appreciate any input from somebody who knows the ins and
> outs of using dual processors.  Thanks  Ed
> [log in to unmask]
>
>                                    P.S. In the past I haven't had
> too much luck from people answering my seemingly stupid questions
> on this forum.  I hope my luck changes this time.

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