UMC Green CPU
The UMC Green CPU was an x86-Compatible Microprocessor produced by UMC of Taiwan in the early to mid-1990's. It was offered as an alternative to the Intel 80486 with which it was pin compatible usually allowing it to be installed in the same motherboard models. All models had Power Management features intended to lower electricity consumption.
Models Produced
The UMC Green CPU was available with different features, physical characteristics and clock speeds.[1] Some of which were only sold in limited quantities.
Available Models
All models feature an 8KB Level 1 Cache and operate at clock speeds of 25 MHz, 33 MHz or 40 MHz.
| Model/Feature | FPU | Package | Voltage | Notes |
|---|---|---|---|---|
| U5S | No | CPGA | 5V | Compatible with the 486SX. |
| U5D | Yes | CPGA | 5V | Compatible with the 486DX, very few were produced. |
| U5SX | No | CPGA, PPGA, PQFP | 5V | Identical to U5S, QFP version available as an embedded solution or attached to a PGA adaptor. |
| U5SD | Yes | CPGA | 5V | Few were produced. |
| U5SF | No | PQFP | 5V | Plastic Package, an embedded solution for smaller computers. |
| U5SLV | No | PQFP | 3.3V | Low Voltage version. |
| U5FLV | No | PQFP | 3.3V | Low Voltage Flat-Pack, Often embedded on the motherboard. |
Production and Fabrication
As one of the largest chip foundry owners in Taiwan, UMC owns several fabrication plants which allowed them to fabricate their own designs, whereas some other manufacturers - notably Cyrix - had to contract this process out to third parties such as Texas Instruments and IBM. All available models of UMC Green CPU were produced on a 0.6 Micron CMOS process.[2] The chips were available in both plastic and ceramic packages for different applications. The majority of PQFP variants were sold to motherboard manufacturers as a low-cost embedded solution.
Performance
The UMC U5 Series design was focused on microcode optimizations. An equivalently clocked Intel or AMD processor required 40 cycles to perform Integer Division where the UMC processors required only 7 allowing the instruction to complete significantly faster. Performance is generally observed to be higher than competing processors on a clock-for-clock basis; The 40 MHz U5S model being comparable to an AMD Am486SX2 at 66 MHz with correctly configured motherboards.[3]
Due to an error in the microcode, Microsoft Windows 98 Second Edition identifies some processors as an Intel Pentium MMX which could cause the operating system and software running within it to crash or exhibit undefined behavior.
Clock Doubling Version
UMC produced a small quantity of clock doubling processors labelled as the U486DX2. These processors were designed to compete with other clock doubling solutions from Intel, AMD and Cyrix but due to ongoing legal troubles UMC withdrew from the market. The processor was only ever produced as an engineering sample and never made it to market.[4] This model was manufactured with a 0.35 Micron CMOS process in a ceramic package.[5]
Legal Dispute
In 1994, Intel alleged that UMC had infringed upon their patent for the Intel 80486 microprocessor.[6] Filing complaints against UMC and it's distributors. UMC countered the claims with an anti-trust suit and the case was eventually settled out of court with UMC withdrawing their product and ceasing production of Intel compatible microprocessors.
As a result of the dispute, all processors were prohibited from sale within the United States and were visibly labeled as such. Placement of this label varies, the ceramic U5S and U5D models typically display "Not for U.S. sale or import" as part of the silkscreen on the top of the chip where the U5SX and U5SD models usually had "NOT FOR U.S. SALE" printed onto the gold Die cover on the underside of the package. This labeling is often absent from plastic packages.
References
- ↑ http://www.cpu-world.com/CPUs/80486/MANUF-UMC.html A page which documents several versions of the UMC Green CPU.
- ↑ http://www.opennet.ru/docs/FAQ/hardware/chiplist-part3.html Web page documenting several processors and their fabrication.
- ↑ https://docs.google.com/spreadsheet/ccc?key=0Aigi3Xn2U-_vdGtKeFpIU2pKWTl2N0J6UFh6Z0E2TWc&usp=sharing#gid=0 Benchmark showing various processors, including the U5S and U5SX.
- ↑ http://www.cpu-museo.it/486umc.html Web page documenting the U486DX2 version of this CPU.
- ↑ http://translate.google.co.uk/translate?hl=en&sl=ru&u=http://www.phantom.sannata.ru/forum/index.php%3Ft%3D13090%26a%3Ddo_print&prev=/search%3Fq%3DUMC%2BU5S%2B0.6%2Bmicron%26client%3Dfirefox-a%26hs%3DVei%26rls%3Dorg.mozilla:en-US:official%26channel%3Dsb Page talking about various UMC Green CPU models which notes the Micron process of the U486DX2.
- ↑ http://www.cpushack.com/2012/09/06/intel-vs-the-world-the-338-patent/ An article which talks about the Intel VS. UMC case.