Editing Pentium OverDrive

{{Short description|Microprocessor developed by Intel}}
The '''Pentium OverDrive''' was a [[microprocessor]] marketing brand name used by [[Intel]], to cover a variety of consumer upgrade products sold in the mid-1990s. It was originally released for [[Intel 80486|486]] motherboards, and later some [[Pentium compatible processor|Pentium]] sockets. Intel dropped the brand, as it failed to appeal to corporate buyers, and discouraged new system sales.

==486 sockets==
[[File:socket3overdrive.png|thumb|Pentium OverDrive for 486 systems]]
[[File:Intel Pentium OverDrive die.JPG|thumb|[[Die shot]] of Pentium OverDrive for 486 systems]]
The Pentium OverDrive is a heavily modified, 3.3 volt Pentium P54 core manufactured on [[600 nm process|0.6 micrometer]] technology. It is fitted with a 486-compatible [[Bus (computing)|bus]] unit (though with an increased pin-count), an integrated [[Heat sink|heatsink]] and fan, and 32 kB of [[CPU cache|level 1 cache]], double the 16 kB offered on regular P54C chips.<ref>[http://groups.google.com/group/comp.sys.ibm.pc.hardware.systems/browse_thread/thread/2c3c8941c073c470 INTEL ANNOUNCES FIRST PENTIUM(TM) OVERDRIVE(TM) PROCESSOR], Press Release, Google Groups, February, 1995.</ref> As the [[data bus]] was effectively reduced to [[32-bit]] width, per-clock performance was much lower than that of a 'regular' Pentium, though still substantially faster compared to a similarly clocked 486 owing to the Pentium's architectural improvements, such as the much improved [[Floating-point unit|FPU]]. It was also equipped with an integrated 3.3 volt [[voltage regulator|power regulator]] as many 486 motherboards only provided 5 volt power.

The 63&nbsp;MHz model was launched in February 1995, and supported 25&nbsp;MHz bus systems. The much faster 83&nbsp;MHz version, which supported both 25 (63&nbsp;MHz effective) and 33&nbsp;MHz bus systems, launched much later the same year on September, and was very expensive at $299 compared to other upgrade alternatives, such as those based on [[Am5x86|AMD's 5x86]] and [[Cyrix Cx5x86|Cyrix's Cx5x86]] chips.<ref name="InfoWorld 1995-09-11">{{cite magazine|magazine=[[InfoWorld]]|date=1995-09-11|df=ymd|last=Crothers|first=Brooke|title=System upgrades: Intel plans OverDrive for Pentium systems|volume=17|issue=37|page=3|issn=0199-6649|language=en-us|url=https://books.google.com/books?id=TToEAAAAMBAJ&pg=PA3}}</ref>

The processor's heatsink is permanently attached, and the removable fan module is powered via spring-like metal prongs that connect to a trio of conductors on the surface of the chip. The clip that releases the fan is visible in the first photo, at the top left corner of the CPU. The central plastic "column" that leads from the center of the fan houses the fan wiring and leads down the side of the heatsink at this corner. The small plastic points at each top left of this column are the locking mechanism for the fan and are released by squeezing them. The opposite corner of the CPU has a latch that locks the fan around underneath the heatsink, by swinging into place upon assembly. The processor monitors the fan and will throttle back on clock speed to prevent overheating and damage if the fan is not operating. This is a predecessor to the internal temperature detection and protection in Intel's modern processors.

===Compatibility and performance===
During development, Intel had changed the design specification, causing various compatibility and performance problems with some boards that were previously fully compatible. For instance, the [[Packard Bell]] 450 motherboard required a specially-designed [[interposer]] to be installed between the processor and the motherboard to cope with the changed specification, with the unfortunate consequence of precluding access to the motherboard's [[level 2 cache]], resulting in sub-par performance.<ref>[http://www.uktsupport.co.uk/pb/mb/450.htm UKT Support page for the Packard Bell 450 motherboard]</ref> In addition, some older chipsets do not support the [[write-back]] functionality of the chip's level 1 cache, which could also reduce performance. However, the majority of [[Socket 3]] motherboards, particularly later (post-1994) [[VESA Local Bus|VLB]] and most [[Peripheral Component Interconnect|PCI]] boards, provide proper support for the Pentium OverDrive including fully operational access to the level 2 cache, and many earlier boards also support the processor with varying levels of compatibility and performance.

Performance-wise, many popular synthetic benchmarks of the time showed the Pentium OverDrive under-performing its much cheaper and higher-clocked rivals, though its real-world performance (given the motherboard cache was being optimally used) could be much different: programs that were floating-point dependent or optimized for the Pentium architecture (as were both becoming increasingly common in the mid to late nineties) derived a more substantial benefit from the Pentium OverDrive, particularly the 83&nbsp;MHz version. In addition, it fully supported programs and operating systems specifically coded for the Pentium architecture, such as many [[emulator]]s, multimedia utilities and even later [[Windows]] operating systems and games; however, the benefit of running such programs on a clock- and motherboard bus-constrained system may be questionable.

===Models===
'''PODP5V63'''
* Introduced February 3, 1995
* 234 pins, P24T pinout
* 5 or 3.3 volts
* L1 Cache 32 kB (16 kB + 16 kB)
* 63 [[Megahertz|MHz]] on 25&nbsp;MHz [[front side bus]] (25 × 2.5)

'''PODP5V83'''
* Introduced September 1995
* 234 pins, P24T pinout
* 5 or 3.3 volts
* L1 Cache 32 kB (16 kB + 16 kB)
* 83&nbsp;MHz on 33&nbsp;MHz front side bus (33 × 2.5)

Some 63 CPU models (part number 109X4405H6J05) have 234 pins instead of 235. Some CPUs came with the pin chopped off (Pin A4) and others had the pin completely missing and covered with the encapsulation.

==Pentium sockets==
{{Multiple image |total_width=350 |perrow=2
| image1   = KL Intel Pentium Overdrive Socket4 b.jpg
| caption1 = Pentium Overdrive for Socket&nbsp;4 without fan
| image2   = KL Intel Pentium Overdrive Socket4 a.jpg|
| caption2 = Pentium Overdrive for [[Socket 4]], 120/133 MHz.
| image3   = KL Intel Pentium MMX Overdrive B.jpg
| caption3 = Pentium Overdrive&nbsp;MMX without fan.
| image4   = KL Intel Pentium MMX Overdrive A.jpg
| caption4 = Pentium Overdrive&nbsp;MMX, 166&nbsp;MHz.
}}

The original [[Socket 4]] Pentium chips ran at higher voltages (5V) than later models. Although little known, Intel did in fact release an OverDrive chip for these sockets, that used an internal clock multiplier of 2, to change them to a "120/133" machine.

*PODP5V120: 120&nbsp;MHz on 60&nbsp;MHz bus
*PODP5V133: 133&nbsp;MHz on 66&nbsp;MHz bus or 120&nbsp;MHz on 60&nbsp;MHz bus

The OverDrive Processors for the Pentium 75, 90 and 100 were also released ([[Socket 5]], 3.3 V), running at 125, 150 and 166&nbsp;MHz (clock multiplier of 2.5). The 125 is an oddity, because Intel never made a Pentium 125 as a stand-alone processor.

*PODP3V125: 125&nbsp;MHz on 50&nbsp;MHz bus
*PODP3V150: 150&nbsp;MHz on 60&nbsp;MHz bus
*PODP3V166: 166&nbsp;MHz on 66&nbsp;MHz bus

These were replaced by Pentium OverDrive&nbsp;MMX, which also upgraded the Pentium 120 - 200&nbsp;MHz to the faster version with [[MMX (instruction set)|MMX]] technology.

*PODPMT60X150: up to 150&nbsp;MHz on 60&nbsp;MHz bus (clock multiplier of 2.5)
*PODPMT66X166: up to 166&nbsp;MHz on 66&nbsp;MHz bus (clock multiplier of 2.5)
*PODPMT60X180: up to 180&nbsp;MHz on 60&nbsp;MHz bus (clock multiplier of 3.0)
*PODPMT66X200: up to 200&nbsp;MHz on 66&nbsp;MHz bus (clock multiplier of 3.0)
{{Clear}}

==Socket 8==
{{Multiple image |total_width=250 |perrow=2
| image1   = Intel Pentium II OverDrive.jpg
| caption1 = Top view of the Intel Pentium II OverDrive CPU with [[heatsink]] and fan.
| image2   = Intel Pentium II Overdrive Engineering Sample.jpg
| caption2 = An [[engineering sample]] version of the Pentium II Overdrive, showing the bottom of the unit.
| image3   = KL Intel PPro Overdrive P6T Top.jpg
| caption3 = Pentium II Overdrive without heatsink. Flip-chip Deschutes core is on left. 512&nbsp;kB cache is on right.
}}

In 1998, the [[Pentium II#Deschutes (Pentium II Overdrive)|Pentium II OverDrive]], part number PODP66X333, was released as an upgrade path for [[Pentium Pro]] owners. Combining the [[Pentium II]] [[Pentium II#Deschutes (80523)|Deschutes]] core in a [[flip-chip]] package with a 512&nbsp;kB full-speed L2 cache chip from the [[Pentium II Xeon]] into a Socket 8-compatible module, this resulted in a 300 or 333&nbsp;MHz processor that could run on a 60 or 66&nbsp;MHz front side bus. This combination also brought together some of the more attractive aspects of the Pentium II and the Pentium II Xeon: MMX support/improved 16-bit performance and full-speed L2 cache respectively. This configuration would be replicated by the later "[[Pentium II#Dixon|Dixon]]" mobile Pentium II core with 256&nbsp;kB of full-speed cache embedded on-die, as well as the later "[[Pentium III#Coppermine|Coppermine]]" and "[[Pentium III#Tualatin|Tualatin]]" Pentium III cores using the same 256&nbsp;kB full-speed cache embedded on-die.

This upgrade could be used in single and dual processor [[Socket 8]] systems. It does not support quad (and even hexa) processor Socket 8 systems due to it lacking four-way or higher multiprocessing, however it can work in two sockets of quad processor Socket 8 systems with CPU 3 and 4 removed. Unofficially, it could also be run in quad and hexa processor Socket 8 systems. This came about after some users upgraded their ALR 6x6 systems with them.<ref>{{Cite web|url=https://arstechnica.com/civis/threads/re-my-custom-alr-6x6-is-now-finished.878654/|title=Re: My Custom ALR 6x6 is now FINISHED!!!!!!|date=December 5, 2001|website=Ars OpenForum}}</ref>

One of the major use cases for these chips was [[Intel]]'s [[ASCI Red]] supercomputer, stationed at [[Sandia National Laboratories]]. This supercomputer was the first computer to break the [[teraFLOPS]] performance mark in late 1996, which up until the upgrade was running dual Pentium Pro CPUs in its nodes since its inception. ASCI Red had all 4,510 CPUs upgraded from dual Pentium Pros to dual Pentium II Overdrives in 1999, making it the first computer to break over two [[teraFLOPS]] after the upgrade while further maintaining its position as the world's fastest on the [[TOP500]] list at the time since it held that position from its first full operations in 1997 up until late 2000, when it was surpassed by [[IBM]]'s [[ASCI White]], a supercomputer stationed at [[Lawrence Livermore National Laboratory]]. ASCI Red then continued to use dual Pentium II OverDrive CPUs for the remainder of its usage until it was finally decommissioned in 2006.

In Intel's "Family/Model/Stepping" scheme, the Pentium II OverDrive CPU is family 6, model 3. Despite being based on the Deschutes core, it identifies itself as a [[Pentium II#Klamath (80522)|Klamath]] Pentium II when queried by the [[CPUID]] command.<ref>{{cite web|url=http://www.heise.de/ct/english/98/18/020/|title=c't - English pages (18_98, page 20)|website=www.heise.de|first=Georg|last=Schnurer|archive-url=https://web.archive.org/web/19990914131901/http://www.heise.de/ct/english/98/18/020/|archive-date=September 14, 1999|access-date=April 12, 2009}}</ref> As noted in the Pentium II Processor update documentation from Intel, "although this processor has a CPUID of 163xh, it uses a Pentium II processor CPUID 065xh processor core."<ref>[http://download.intel.com/design/PentiumII/specupdt/24333749.pdf Specification Update for the Pentium II Processor, page 15, note 3<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20110831012432/http://download.intel.com/design/PentiumII/specupdt/24333749.pdf |date=2011-08-31 }}</ref>

==See also==
*[[Intel 80486 OverDrive]]
*[[RapidCAD]]

==References==
{{reflist}}

==External links==
*[https://web.archive.org/web/20071226040914/http://www.pcguide.com:80/ref/cpu/fam/g5P54OD-c.html Intel Pentium OverDrive (Archive.org)]
*[http://www.cpu-world.com/CPUs/Pentium/TYPE-Pentium%20overdrive.html Pictures of Pentium OverDrive]
*[https://web.archive.org/web/19980128144450/http://support.intel.com/support/processors/overdrive/#anchor3 Former Intel Pentium OverDrive support page]
*[https://web.archive.org/web/20130410145021/http://www.intel.com/p/en_US/support/highlights/processors/overdrive|archive-date=April 10 2013 Intel Pentium OverDrive support page (Archive.org)]

{{Intel processors|discontinued}}

[[Category:Intel x86 microprocessors]]
[[Category:Computer hardware tuning]]
[[Category:Coprocessors]]
[[Category:Computer-related introductions in 1995]]