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From: americast-post@AmeriCast.Com
Organization: American Cybercasting
Subject: The PC: The Next-Generation FEA Workstation
Date: Mon, 28 Sep 92 17:04:47 EDT

This is an actual portion of the Mechanical Engineering Magazine
as distributed by American Cybercasting Corporation.  Contact
usa@americast.com for further information.



The PC: The Next-Generation FEA Workstation
W. Charles Paulsen



It has taken only 11 years for the personal computer, or PC, to 
rival the speed and performance capabilities of workstations. And 
that's good news for engineers involved in finite element analysis 
(FEA) who need a great deal of computational power but welcome the 
convenience of PCs. Test comparisons conducted recently by design 
and analysis software manufacturer Algor Inc. (Pittsburgh) show 
that in fact the PC has caught up, see Table 1. However, it is 
important to remember that overall performance depends not just on 
CPU speed, but on the graphics board, bus, disk drive, and other 
elements as well.
  The maturation of the PC as a platform for FEA may surprise 
skeptics because of the relatively short time it took the computer 
to reach its current stature. It was in August 1981 that Armonk, 
N.Y.-based IBM Corp. introduced the microprocessor it called the 
PC. Today's PC is a far cry from the 1981 original (see "A Brief 
History of the PC," page 66). The 32-bit 80386, which is 
practically an entry-level machine these days, was the first 
computer to be considered a workstation alternative.
The 80486 Workstation
  The 80486 directly competes with workstations. Its one chip 
combines a microprocessor (80386), a floating-point math 
coprocessor (80387), a memory cache controller (82385), and 8 
kilobytes of RAM cache.
  For a long time, the 640-kilobyte maximum memory limit imposed 
by DOS was a problem. Back in August 1981, 640 kilobytes seemed 
like plenty of memory. Switching to OS/2 or Unix operating 
systems, which do not have the 640-kilobyte barrier, is an 
alternative, but the user community refuses to change. No one 
wanted to give up the familiar DOS. Now, everyone can keep DOS 
with the introduction of extenders that allow DOS applications to 
run into extended memory. In February 1988, Algor introduced its 
Hyper series of products that under DOS take advantage of extended 
memory. With this technology, software can access as much extended 
memory as is available-similar to a mainframe. Engineers now can 
perform and solve monster-size problems.


The War of the Operating Systems

  DOS extenders have increased the life span of DOS for many 
years. Eventually, a pure 32-bit operating system will emerge. 
Microsoft's Windows 3.1, which must be used with DOS (preferably 
5.0), attempts to satisfy some of the demands of software 
developers but it is still a 16-bit system at heart. IBM's new 
product, OS/2 version 2.0, introduced in April 1992, is a true 32
-bit system. It requires an 80386 chip or better, 4 megabytes of 
system RAM, and 31 megabytes of free hard disk. OS/2 can run 
standard DOS and Windows applications as well as applications 
specifically written for OS/2. Applications that take full 
advantage of protected memory will come in the future.
  By the end of 1992, Microsoft will release its 32-bit system, 
Windows NT (New Technology), which will be a direct challenge to 
OS/2. Windows NT, which is rumored to have a Unix flavor, will run 
on RISC and Intel processors. Fortunately, the competition between 
OS/2 and Windows NT will keep prices down. Dark-horse candidates 
could also emerge as winners. The Apple/IBM alliance will 
introduce an operating system called Taligent. Sun Microsystems 
Inc. (Mountain View, Calif.) spun off a software division that is 
marketing Solaris. And finally Steve Jobs, a cofounder of Apple 
and now president of Next Computer Inc. (Redwood City, Calif.), is 
ready to ship a PC version of his heralded NextStep OS.


How Fast is Fast?

  Whetsone, Dhrystone, Linpack, SPEC benchmark suite, mflops, and 
mips are all names to measure how fast a computer runs a program. 
In the world of FEA, Algor has established a few standard 
engineering stress-analysis models. By running the models on 
various PC and workstation configurations, the capabilities of the 
machines are readily quantified. The clock is the judge.
  Unfortunately, configuring an optimum PC today is not simple, 
given the many options available. What was a throughput bottleneck 
yesterday, goes away only to be replaced with another bottleneck 
today. For example, hard disks were a bottleneck, but with 
electronic disks in RAM and disk caching, the CPU speed is now 
critical.


A Guide to Specifying And Purchasing a PC

  Manufacturers can build a computer to exact specifications. A PC 
can perform like a workstation if it has the newest technology. 
With the power of mass marketing, the purchase price will be lower 
than that of a conventional workstation.
  The fundamental rules to keep in mind are: Faster is better than 
fast and silicon is better than iron. So when purchasing a PC 
there are several things that should be considered to ensure that 
the computer will effectively respond to the demands of the task 
at hand.
* Source. If you can replace the batteries in a flashlight or 
remove the cover of a PC, you can order your computer from a mail
-order house. Most mail-order firms are reputable, and service is 
not an issue since "repairing" is nothing more than swapping 
components.
* CPU. Buy the fastest 80486DX you can afford. Do not buy a 
80486SX and an 80487. The 80486DX has a built-in math coprocessor 
that is ideal for FEA-type analysis and an 8-kilobyte memory 
cache. Machines of 33 MHz are readily available; 40- and 50-MHz 
machines are already shipping in quantity. In February 1992, Intel 
released a line of chips called the clock-doubler 486 family 
(officially referred to as the 486DX2). A clock-doubler processor, 
when replacing the regular 25-MHz DX chip in a machine designed to 
run at 25 MHz, will run internally at 50 MHz and will 
automatically slow down externally as the system board requires. 
There are some BIOS (basic input output system) chip-compatibility 
issues to be ironed out; the first round of machines to 
incorporate this chip will be of the OEM variety. By late 1992, 
there should be a retail version of the DX2 so that owners can do 
the upgrading. Clock-doublers are currently shipping for 25-MHz 
machines, but expect a 33-MHz doubler that will run at 66 MHz 
later this year. A 50-MHz doubler has been rumored. Soon, anyone 
will be able to double the speed of his or her computer by simply 
popping in these chips.
* Bus. The latest, best, and most popular 32-bit bus is the EISA 
bus. It should prove to be a good investment for a few years. 
Owners of pure IBM machines have no choice-they get the MCA bus.
* Hard disk. The first XT had 10 megabytes of storage and an 
access time of 110 milliseconds. An entry-level workstation PC 
should have at least 100 megabytes with an access time approaching 
15 milliseconds. Serious FEA users should consider a 320-megabyte 
disk as a minimum. Since DOS 5.0 increased the partition size from 
512 megabytes to 2 gigabytes, monster machines with 2 gigabytes 
are feasible.
* Disk interface. The disk interface is the connection between the 
disk drive and the system bus. It determines the speed at which 
data can be transferred between them. The original ST506 and the 
ESDI were device-level interfaces that required a separate 
controller, both are now obsolete. The new wave is toward system-
level interfaces, where the controller electronics are on the 
drive and require only an unsophisticated host adapter (IDE or 
SCSI). The IDE (integrated drive electronics), which conforms to 
ANSI's AT attachment standard, can transfer up to 4 megabytes per 
second and is favored for 200-megabyte disks and smaller. Small 
Computer System Interface (SCSI) currently sports two standards. 
SCSI-1 was adopted in 1986 and has a data-transfer rate of 5 
megabytes per second, 20 percent faster than IDE and twice as fast 
as ESDI. SCSI-2, adopted in 1990, can support 10 megabytes per 
second on a single cable and 40 megabytes per second on a double 
cable. Besides being faster, it can support up to seven devices 
(including printers, scanners, and CD-ROM) daisy chained together. 
SCSI is the interface of choice for larger-capacity hard drives. 
There is one small problem: you cannot plug just any SCSI 
peripheral into any SCSI adapter because vendors have not settled 
on one driver protocol. There are three protocols fighting to 
become the standard, Layered Device Driver Architecture (LADDR) 
from Microsoft; ASPI (Advanced SCSI Programming Interface) from 
Adaptec Inc. (Milpitas, Calif.), and Common Access Method (CAM), a 
proposed ANSI standard in concert with Apple Computer, a long-time 
SCSI advocate. Since Adaptec is an adapter board manufacturer, 
rival manufacturers did not want to endorse a competitor's 
standard; thus CAM was created. It appears that ASPI has a good 
shot at becoming the de facto standard. De facto standards based 
on market acceptance almost always beat out committee standards. 
Finally, with SCSI, multiple disks can be combined into one 
logical volume, a technical accomplishment for FEA users who want 
to do monster-size problems. Software vendors have long used disks 
as virtual memory to further extend the PC into the domain 
formerly held by mainframes. Because the SCSI standard is still 
unsettled, an adapter must be checked with the hard drive-or get a 
written compatibility claim.
* Memory. Buy as much memory as possible. In the technical world 
of computing, everything improves with more memory. Memory is 
cheap and it is getting cheaper. A million bytes are now $17 and 
dropping. The 80486 can address more than 4000 megabytes (4 
gigabytes) of extended memory, a long way from the original PC's 1 
megabyte. Now that software applications can take advantage of 
this memory through DOS extenders, it will be put to good use. 
This is particularly true for FEA problems. Algor's Hyper series 
products can now run large-size problems totally in memory.
  The memory can be added through memory boards on the external 
bus. However, this is the least-preferred way because the memory 
access is slow due to the bus speed limitation (although MCA 
boards are reported to be quite fast). It is best to add memory 
right on the system board, usually in the form of single in-line 
memory modules (SIMMs), because then memory access is at the 
fastest rate possible. The initial wave of 80386 machines allowed 
for a maximum of 16 megabytes on the system board. With the 80486 
machine, manufacturers are allowing for up to 256 megabytes on the 
system board.
* Disk caching. It is faster to read or write to memory chips than 
to perform the same tasks with magnetic media. Hard disk designs 
have a lower limit of about 12 milliseconds for average seek time, 
far slower than the time required to access data in memory. A disk 
cache dynamically duplicates part of the contents of your hard 
disk in fast RAM so that it can be read (and sometimes written to) 
at RAM speed. DOS provides a dumb disk cache through its BUFFERS 
command in the CONFIG.SYS file. It is called dumb because it 
blindly loads data from the hard disk to memory that has been 
allocated in the CONFIG.SYS command line. A more sophisticated 
disk cache has a memory-management program scheme that attempts to 
anticipate an application's requests for disk data. Software that 
provides this service is available from several commercial 
sources. PC-Kwik from Multisoft Corp. (Beaverton, Ore.) 
consistently gets good reviews. Microsoft's SMARTDRV.SYS (free 
with Windows 3.1) is another such program. All these methods 
borrow the RAM from the system.
  A more sophisticated alternative is a caching disk controller in 
which the caching RAM is on the controller. Controllers with up to 
16 megabytes of cache memory are available, but their current high 
prices are hard to justify over the software approach, which many 
believe is as good. No matter which method is selected, caching is 
recommended when hopping between several applications. If a 
dedicated power program such as Algor is being run, however, 
running with a little cache and the maximum amount of extended 
memory should be considered. A couple of test runs should 
determine the best combination.
* Memory caching. The time it takes a processor to execute a 
command is directly controlled by the clock. The time it takes the 
processor to retrieve information from memory is called the 
processor bus cycle. For the current family of Intel processors, 
it takes two processor cycles to execute one bus cycle (P/B 
ratio). The inverse of the CPU clock speed times, the P/B ratio is 
a direct measure of how fast the memory must be. The first PC had 
a clock of 4.77 MHz, thus the minimum memory speed was 420 
nanoseconds. The RAM in the early days was faster, in the 160-
nanosecond range. In other words, the RAM was faster than the CPU. 
Today's situation is reversed. A 33-MHz machine would require 60 
nanoseconds or faster RAM. Dynamic RAM can just meet this 
requirement, as the fastest readily available RAM clocks in at 
around 60 nanoseconds. Faster CPUs are now RAM speed limited. As a 
consequence, today's faster computers include memory caching, 
which uses superfast static RAM (SRAM) to cache the transfer 
between the CPU and system memory. These chips are right on the 
system bus and are officially called secondary cache. SRAM chips 
can run as fast as 15 nanoseconds, fast enough to barely keep up 
with 50-MHz 80486s. The intelligence to do this is hard coded into 
a new breed of chips called caching controllers, which are now an 
integral part of the system board. Computer manufacturers can get 
quite creative with designing and specifying these controllers. A 
bus cycle in which the data requested are not in the cache is 
called a cache miss (cache misses dramatically slow the processor 
down). Similarly, when the data are already in the cache, it is 
called a cache hit. The ratio of cache hits to the number of 
attempts to access the cache is called the hit rate, which is the 
key to performance. A well-designed memory cache should have a hit 
rate well above 95 percent. SRAM memory caches usually are 64, 
128, or 256 kilobytes in size. The organization of the cache can 
be fully associative, direct-mapping, or set-associative, all 
intended to increase the hit rate.
  The 80486 CPU provides the ultimate in memory caching. It has 8 
kilobytes of memory, called primary memory cache, built right into 
the chip. This is one of the reasons that the 80486 chip is the 
workstation CPU of choice.


The Graphic Wave

  Nowhere has change been more visible than in the graphics area, 
with technological improvements occurring at an almost exponential 
rate. IBM was slow to offer engineering-quality graphics boards. 
The initial PC resolution was 320-by-200 pixels with four colors, 
or 640-by-200 pixels in black and white-not good enough for CAD 
and FEA. The lack of good graphics was an opportunity for third-
party graphics board manufacturers to enter the market.
  In August 1984, IBM announced the 80286-based AT computer and 
the EGA graphics card, which offered 16 colors at a resolution of 
640-by-350 pixels. In April 1987, IBM announced the VGA graphics 
board with a 640-by-480-pixel resolution and the 8514/A graphics 
board with 1024-by-768 pixel resolution. Board manufactures 
introduced Super VGA boards with 800-by-600 and 1024-by-768 pixel 
resolutions. Each board had its own specifications, making it 
difficult for software vendors. Clone vendors banded together in 
April 1989 and formed the Video Electronics Standards Association 
(VESA).
  The new kid on the block is IBM's XGA with 1024-by-768 pixel 
resolution and 256 colors, which was introduced in October 1991. 
This is the first board to uncork the 16-bit bus bottleneck, as it 
can use a 32-bit bus.


What's Next?

  Predicting the future is easy. Computers will get smaller, 
faster, cheaper, more graphical, and more powerful. DOS will 
continue to improve and is destined to run in protected mode; that 
is, it will crack the 640-kilobyte barrier. A graphical user 
interface sitting on top of DOS, such as Windows, is a given, 
although the engineering community may elect to use the interface 
supplied with the major applications they use. For example, Algor 
provides one built right into its products.
  Intel has been king of the mountain during this whole PC 
revolution. It is not taking the RISC workstation challenge 
lightly. In 1991, Intel spent $1.5 billion on research, 
development, and capital expenditures. In 1992 it expects to spend 
$2 billion. The PC, as we know it, is not going to stop improving 
with that kind of support behind it.  Sometime in the second half 
of this year, Intel is expected to begin shipping the P5 (80586). 
It will be superscalar, which means that more than one instruction 
can be decoded, dispatched, and executed during each clock cycle. 
(The 80486 can handle one instruction per clock cycle; the 80386 
can handle one per two cycles.)
  The P5 will have two integer units and  a  floating-point  
instruction.  Integer operations will be twice as fast as the 
80486, while floating-point operations will run five to seven 
times  faster.  The  P5  will  have two internal  memory  caches,  
one for instructions and one for data. The Intel i860, which is 
not a DOS machine but is currently available, is similar to the 
P5. Many advanced software companies are working with the i860 in 
anticipation of the P5.

Copyright 1992, Mechanical Engineering.

For more information, send-email to American Cybercasting Corporation
(usa@AmeriCast.COM)
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