Pentium II, K6 and 6x86MX CPUs Live Up To Expectations (01jun97)

June 1, 1997

Computers featuring the new Intel Pentium II, AMD K6, and Cyrix 6x86MX central processing units (CPUs) are now widely available in the market, so we decided to take a look at some underlying details regarding these workstation-class processors.

The Pentium II has turned out to be more than just a multi-media enhanced Pentium Pro. The new processor heralds a new mini-motherboard design for the processor and the L2 cache, it runs 16-bit operating system code and applications with no penalties, and the speeds are faster.

Pentium II Easier to Build, Less Elegant, But Still Faster

The Pentium Pro contained its processor and L2 memory cache next to each other in one piece and both ran at the same clock speed. This yielded great performance but apparently was difficult to manufacture. While we can’t say exactly what occurred at Intel with regard to the Pentium Pro’s evolution, this manufacturability issue probably drove the redesign more than anything else.

The Pentium II has essentially become a mini-motherboard (or daughter card) of discrete components encased as a cartridge that plugs into a computer’s motherboard. This breaks away from the tradition of more components on a single chip.

The CPU inside the cartridge is smaller, and as a result, it is faster since the electrical signals have less distance to travel. The L1 memory cache inside the chip has grown from 16K to 32K (16K instruction/16K data). The L2 cache has grown from the prevalent 256K to a standard 512K, but the distance to the CPU increased and the L2 memory speed dropped to half that of the CPU.

This overall arrangement still results in better performance since the processor can store more information in the L1 and L2 caches before going to main memory which is dramatically slower.

No 16-Bit Limits, Plus MMX

The Pentium Pro actually ran 16-bit code slower than its Pentium siblingsdid as a result of the assumption that users would be primarily using 32-bit based programs. Thus, the Pentium Pro architecture did not incorporate features that were 16-bit oriented such as frequent updates of its segment registers.

The Pentium II architecture incorporates faster updates as well as the 57 new instructions for multimedia (the MMX capability). The hardware and software architecture changes result in PCs that technically run faster although Pentium Pro users using Windows NT and 32-bit programs are unlikely to notice any dramatic differences.

For many companies there is a noticeable benefit to this 16-bit code efficiency. Setting up and managing Windows 95 is easier than Windows NT. Small businesses can network and install new computer devices on their own without the PC experts that are often required for NT (UNIX is much worse). However, Windows 95 isn’t an option if your primary programs and/or hardware do not run with Windows 95 or if you want the security options available with NT.

Other Considerations

Pentium II CPUs are limited to single and dual multi-processor configurations for the near future. That’s fine for workstations as we have seen with a loaned Intergraph 425 TDZ running leading CAD/CAM and analysis applications. Meanwhile, servers that need four processors will continue to be made with Pentium Pro CPUs.

It turns out that the Pentium II has some sort of esoteric computational bug. Intel says it is working on a software fix, but in-depth tests by IBM have not found any problems running applications. We appreciate Intel’s handling of the matter, and we don’t think the bug is worth delaying any Pentium II purchases you may be planning (we’re buying one ourselves).

Lower administration PCs (NetPCs) have also been demonstrated with the Pentium II. A few vendor tests have demonstrated Pentium II PCs being fully configured over a network by a server. For big companies, this will be of immense help if it works.

Clone CPUs Face A Lock-Out

The Pentium II’s cartridge holder talks to the rest of the system via a new connection called Slot 1 and a proprietary bus on the motherboard called the P6 bus. The P6 processor bus currently runs at the same speed, 66 MHz, that the previous non-proprietary Pentium bus ran at. But Intel plans to increase this to 100 MHz by 1998 with new motherboard chipsets that will provide additional undisclosed features.

The extra performance sounds great although the proprietary PxGET http://siteinfo.a9.com/data/6lSv01dR0100Ll?cli=10

How Will MMX Affect CAD Performance? (01mar97)

March 1, 1997

A new wave of Pentium PCs is currently hitting the market using Intel microprocessors that incorporate an expanded instruction set called MMX (MultiMedia eXtension). Although the correct name for these chips is the P55C, don’t expect to see that used very much. Everyone will refer to these systems as simply being MMX-based. The technology is also being offered (via licensing) in microprocessors sold by Cyrix and in the near future, by Advanced Micro Devices.

MMX adds 57 new instructions to the traditional x86 architecture. These instructions are tuned to enhance the type of arithmetic operations that commonly occur in video, audio, and similar applications. That’s why these instructions carry the multimedia nomenclature. The big question is what does this mean to users of typical engineering design software? It turns out that at a given clock speed, these systems will function 10% to 20% faster, but not because of the MMX instructions. Performance for the 200-MHz chip is 6.4 SPECint95 and 4.7 SPECfp95. This is comparable to what Silicon Graphics offers with a R5000/180SC O2 workstation.

Intel did more than just add new instructions when it redesigned the Pentium microprocessor. The company doubled the size of the internal cache memory to 32 KB and redesigned some of the chip’s internal logic. This is the major reason for an increase in general system performance.

Improved Graphics Performance

Eventually we will see substantial improvements due to MMX in visualization and animation packages, (such as VisFly, Lightscape and 3D Studio MAX), when these programs are re-compiled to incorporate MMX instructions. That could be in late 1997 or beyond, depending upon customer demand and competitive pressures. The use of MMX instructions could result in a 50% or better performance improvement for some functions.

One of the problems facing developers of technical applications is that the MMX instructions conflict with the execution of traditional floating point operations. Programmers need to be careful to clearly segment the two types of computing and to ensure when one program takes over the machine from another in a multi-tasking environment, that the program understands what execution state the system is in. This is properly done by the operating system, but we have not heard of anything Microsoft is doing with Windows 95/97 or Windows NT 4.0 to mitigate the problem.

Future Pentium Developments

By mid-year, Intel will be offering MMX capability with its Pentium Pro microprocessors. Known as Klamath, it will incorporate internal cache and other architectural changes as well as come in faster versions. Our understanding is that these will initially run at speeds up to 266-MHz compared to the current 200-MHz maximum. Vendors, such as IBM, plan to offer Klamath-based machines shortly after Intel releases this new microprocessor.

Most PC vendors have already switched over to MMX Pentiums for their mid-range 166-MHz and 200-MHz systems and, as far as we can tell, customers are paying little, if any, premium for these machines. By mid-year, Intel will also be shipping 233-MHz MMX-enabled Pentiums.

For the past year or so, we have been concerned that Intel was falling behind in the raw speed aspects of microprocessor manufacturing. While companies such as Digital were pushing 500-MHz, Intel was stuck in the 200-MHz range. We realize that Digital’s Alpha and the Pentium or Pentium Pro cannot be compared strictly on a clock cycle basis, but clock speed does say something about how advanced a company’s manufacturing capability is.

Intel sought to set these fears to rest recently when it disclosed that it had Pentium Pro microprocessors running at up to 451 MHz in the laboratory. Moving from the laboratory (at 451 MHz, the Pentium Pro requires an ice-water heat sink) is not a simple step but we are comfortable in expecting 300-MHz Klamath systems by the end of this year and 400-MHz systems in 1998.

Finally, we recommend that users move cautiously when implementing MMX-enabled software in a design environment. What works well for playing games might cause problems in the design office. If you need more performance and can wait several months, you might want to see how Klamath turns out in this regard before you buy additional Pentium Pro systems.