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PC vs Mainframe

Tom Knowlton
Tom Knowlton asked
I have 3 to 4 page paper for class, comparing and contrasting PCs vs Mainframe computers.

I plan to address the following areas that I have thought of to compare/contrast:

Physcial Size

Can anyone recommend some good websites to get me started?
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Kyle SchroederEndpoint Engineer

The home of the mainframe, IBM: http://www-1.ibm.com/servers/s390/pes/
These aren't the mainframes of the 70's and 80's...these things are still big boxes, but pack quite a wallop.

This should be a pretty straightforward paper, since the differences vastly outweigh the similarities...

Tom KnowltonWeb developer



LOL...yeah, not much in common (from what I have found so far)

Like the elephant and the ant, are the mainframe and the PC.
Tom KnowltonWeb developer


Found a good one at:


Excellent portayal of Mainframe vs PC.

The Mainframe really shines in Total Cost of Ownership vs the PC as you add more and more users, although the initial setup cost is huge vs the PC.
Tom KnowltonWeb developer


HERE is what I have so far:

Paper 2
PC vs Mainframe

In this paper I will first discuss some general differences between the PC and the Mainframe.  Then I will specifically discuss two major areas where the two systems have noticeable, specific differences:  I/O and Cost.
General Differences
The first obvious difference between a PC and a Mainframe computer is size.  A PC is about 18" square and maybe 8" wide.  You or I could lift one and carry it around easily.  With little or no training most people could take one apart and install a new component like a modem or sound card or hard drive (this is commonplace with PCs).  You can go buy a PC at most computer stores for $1000 to $1500 for a very nice, powerful system.
Mainframes are very expensive, large in size, and very heavy.  They are usually as tall or taller than man.  They are installed in temperature-controlled rooms with limited access from authorized personnel.  They are not portable, at all.  Maintenance is usually carried out by a third-party under strict, multi-million dollar contracts.
Most PCs will have one or two hard drives, with 40 Gigabytes of hard drive space each, and 256 to 512 MB of RAM.
Mainframes on the other hand, come with hundreds of hard drives in a sophisticated RAID array with 30+ Terabytes (Terabyte = 1,000 Gigabytes) of storage capacity.  (From:  http://www.101com.com/solutions/storage/article.asp?articleid=4752)
Typically Mainframes will have Gigabytes of memory.
      Most PCs will run Windows and function as Clients in a network environment.  
Mainframes exist only as Servers and typically run some form of UNIX/Linux.

Noticable, Specific Differences
Mainframes have a much larger I/O bandwidth than PCs.

From:  http://os390-mvs.hypermart.net/mainpc.htm:

The new zSystem that runs on newer Mainframes can support 24 Gigabit Ethernet connections or 36 100 MB FICON connections at wire speed.
Mainframes have a technology called PARALLEL SYSPLEX.
PARALLEL SYSPLEX  is a way of writing serial code and having it work parallel across multiple mainframes without the programmer having to know about it.
It's miles/kilometers ahead of anything in the non-mainframe world. It takes the mainframe to a new level that the others can't match at this time, and probably never will. This is because it requires control of the middleware that is not available on the PC - due to too many different suppliers and no agreement on how to achieve the result.

In contrast, there are very few UNIX or Intel boxes that can even get 24 Gigabit Ethernet connections and those that can normally only have 4-8 independent IO busses and therefore every 3 - 6 cards are sharing the same IO bus and the buses are only running at just over 1 Gigabit. If you have 3 Gigabit cards sharing the same gigabit bus, you are not going to be able to drive all 3 cards to a gigabit. I have not seen any test recently, but about a year ago the fastest Intel box could only get about 800 mbps.

From:  http://consultingtimes.com/Serverheist.html
There are a lot of variables when comparing the costs of PC vs Mainframes.  The PC is the best choice under a certain ceiling of users.  As the number of users increases than the PC becomes cost-prohibitive vs the Mainframe.
Consider this Total Cost of Ownership for comparable PC networks vs a Mainframe solution:
Intel Servers (11 x $8K)                                           $ 88,000
NT Licenses (11 x $600)                                           $ 6,600
Exchange (5,000 mailboxes x $50 per seat)                               $ 250,000
Communication racks (2 x $2.1K)                                     $ 4,200
Networking (2 x $3K) $ 6,000 Facilities ($18 sq. ft/mo. x 104 sq. ft)       $ 67,392
Electricity ($.85 per day per server)                                     $ 10,098
Uninterruptible Power Supply (UPS)                               $ 135,000
Support (4 @ $55K x 1.5 for benefits)                               $ 990,000
Three-year TCO                                                 $1,557,290

IBM 9672-X27 z/VM and ESS                                     $1,252,100
Linux License (1 x $250 + 3 x $35K)                               $ 105,250
Groupware (5,000 mailboxes x $14.2 per seat)                         $ 71,000
Communication rack (1 x $2.1K)                                     $ 2,100
Networking (1 x $3K)                                           $ 3,000
Facilities ($18 per sq. ft/mo x 400 sq. ft)                               $ 259,200
Electricity ($32 per day)                                           $ 34,560
Uninterruptible Power Supply (UPS)                               $ 135,000
Support (one @ $90K, three @ $55K x 1.5 for benefits)                   $1,149,000
Three-year TCO $3,011,210

Divide the TCO by 5,000 users and 36 months, and the mainframe groupware solution comes out to $16.73 per user per month -- almost double the cost of the PC solution!
But this conclusion is deceptive without proper perspective.  
The Mainframe solution really shines as you add more and more users.  Notice the slow growth in Mainframe TCO as more and more users are added to a Mainframe solution vs the PC / Server.
Servers            Mailboxes      Exchange/Intel      Linux/IBM
10            5,000            $ 1,557,290            $ 3,011,210
20            10,000            $ 1,989,580            $ 3,056,210
40            20,000            $ 2,854,160            $ 3,126,010
50            25,000            $ 3,286,450            $ 3,160,960
70            35,000            $ 4,151,030            $ 3,230,710
90            45,000            $ 5,015,610            $ 3,300,660
100            50,000            $ 5,447,900            $ 3,335,210

You can mention that 1999 (might want to research that to make certain) was the first year IBM had more revenues from PC sales than from mainframes.  Although since then I think the trend has reversed back to more revenues from mainframes.
Tom KnowltonWeb developer



Interesting tid-bit!
another interesting fact is that Microsoft are edging back to a Mainframe licencing model with XP.

In other words they have recognised that PC users no longer see much of a need to upgrade basic apps like word. Microsoft therefore have a problem as their revenue will decrease if they stick to a single purchase fee for software. As Mainframe users typically pay a hefty yearly fee for maintenance then the revenue is generated for the whole life of the product.

Another sub-topic could be the hybrid products such as clusters. In the past the Mainframes were the fastest, now the fastest are clusters of micro computers.

Tom KnowltonWeb developer


Thanks everyone!