Editing exponential technology/x704

{{expotech title|X704}}
{{ic family
| title             = X704
| image             = Exponentials 533MHz X704.jpg
| caption           = 533MHz X704 Promotional Picture
| developer         = Exponential Technology
| manufacturer      = Hitachi
| type              = Microprocessors
| first announced   = October 21, 1996
| first launched    = 
| production start  = 
| production end    = 
| arch              = 
| isa               = PowerPC
| microarch         = X704
| word              = 32 bit
| proc              = 500 nm
| tech              = BiCMOS
| clock min         = 410 MHz
| clock max         = 533 MHz
| package           = CBGA-359
| socket            = 
}}
'''X704''' (stylized as '''X<sup>704</sup>''') was a family of high-performance [[PowerPC]] [[microprocessor]]s announced by [[Exponential Technology]] in [[1996]]. At the time, these chips ran over three times the clock rate as [[Motorola]]'s/[[IBM]]'s or [[Intel]]'s (albeit not as fast in direct performance). Exponential experienced a few bumps in the road during the final stages delaying the final product and hindering their initial performance which did not meet their expected performance and power goals. Additionally, the X704 was caught in the crossfire between [[Apple]] and [[Macintosh clone]] manufacturers,  which ultimately sealed their fate (See [[#History|§ History]]).

== History ==
{{see also|Exponential Technology}}
Exponential took on a very ambitious challenge of designing a PowerPC [[microarchitecture]] from the ground up that could operate at extremely high clock frequency for the time - 533 MHz. Comparable chips at the time of Exponential founding were operating at only 50-75 MHz max. By [[1993]] the idea was backed by [[Apple]] and their CEO [[wikipedia:Michael Spindler|Michael Spindler]] which became the principal investor of the newly created company, [[exponential technology|Exponential]].

In [[1994]] [[Apple]] and Exponential signed a joint development agreement and later that year they formed an agreement with [[Hitachi]] which agreed to manufacture their chip at their [[BiCMOS]] foundry. By [[1996]] with their chip just months away from [[engineering sample]], Apple's CEO, then [[wikipedia:Gil Amelio|Gil Amelio]] extended their agreement to gain exclusive rights to the chip for the first nine months of [[volume production]]. The deal included a $5 million prepayment - a payment Apple never delivered. 

First samples of the X704 came back running at only 410 MHz, 88% of the expected speed (or 75% of the top tier model). Exponential attributed the issue to a bug in their custom design tools. This pushed back the deliver date to March of [[1997]]. Even then, the chip would have been considerably faster than the fastest chips on the market at the time - Intel's {{intel|Pentium II|Klamath}} which ran as high as 233 MHz.

By February of [[1997]], the X704 was ready - hitachi delivered Exponential over 7,000 410-MHz chip. Apple was in a fairly bad shape at the time, with massive layoffs on the horizon; just a month later they acquired NEXT software for $430 million, bringing back Steve Jobs as an advisers and replacing key Apple upper management. Around the same time, Exponential displayed an X704-based machine to journalists at the LA [[wikipedia:Dreamworks|Dreamworks Studios]], running complex 3D animations and wowing the audiences. Following Exponential progress [[IBM]] announced a new chip: the {{ibm|Mach 5}}; the chip didn't actually arrive until 5 months later. While clocked at only 250 MHz, its considerably larger cache and wider datapath promised to match X704's performance. IBM chip was also to be manufactured on their new [[0.25 µm process]] (compared to X704's [[0.5 µm]]). Apple eventually went with IBM's chip but only for a short time as by 1998 they went over to PPC 750 series. In a meeting that took place on March 3 1997 Apple told Exponential that with the lay off of thousands employees they will no longer be able to design a system around the X704 chip. This decision had devastating consequences for Exponential which relied on Apple's deal which would've meant hundreds of millions of dollars in revenue.

Running out of cash, as a last resort, Exponential attempted to close a number of deals with a number of [[Macintosh clone]] manufacturers. Exponential had deals on the table with companies such as [[Umax Computer Corporation]], [[Power Computing Corporation]], and [[MaxxBoxx]]. Clone deals where on condition Apple would modify their ROM. In mid-April Apple agreed to provide clones with a modified ROM but at higher charge (supposedly proportional to the processor speed used).

On April 17, 1997 Apple cancelled their existing contract with Exponential, invoking the 'design flaw' clause citing the slower clock speed as the reason. Under the contract Apple was required to pay $1.4 million cancellation fee. The $1.4 was never paid; money that would have more than likely kept Exponential going for a fair mount of time. As a last straw; Apple never delivered the promised modified ROM.

The likely intentional final steps by Apple to block any and all clones from getting their hand at the X704 halted any sale deal Exponential had. On May 8 Exponential ended up laying off 25% of their engineers. After additional attempts by Exponential to collect on the cancellation fees Exponential finally shut down their development center in San Jose on May 15.

On September 1 1997, Exponential sold their X704 patent portfolio, which amounted to over 50 patents, to S3 Inc for around $12M. Many of the technologies in these patents were used in Intel's {{intel|Pentium II}} processors. On December 1998 S3 Inc and [[Intel]] announced a 10-year patent cross-licensing agreement which gave Intel to much of Exponential's original technology.

== Members ==
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<table class="wikitable sortable">
<tr><th colspan="4" style="background:#D6D6FF;">X704 Processors</th></tr>
<tr><th>Model</th><th>Announced</th><th>Launched</th><th>Frequency</th></tr>
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 |?base frequency#MHz
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{{table count|col=4|ask=[[Category:microprocessor models by exponential technology]][[instance of::microprocessor]][[microprocessor family::X704]]}}
</table>

== Architecture ==
{{main|exponential_technology/microarchitectures/x704|l1=X704 Microarchitecture}}
The X704 was an ambitious project for any company let alone a brand new start up. Many of the design tools were inadequate for the task and required Exponential to developed many new tools in-house including a custom [[standard cell|standard cell]] [[standard cell library| library]]. The final product was a {{ibm|PowerPC 60x}}-compatible, IEEE 1149.1-compliant, and IEEE 754-compliant [[microprocessor]] operating at over 400 MHz supporting a bus at up to 100 MHz.

The microprocessor itself was rather unique for its time, taking advantage of [[Hitachi]]'s [[0.5 µm]] [[BiCMOS]] process technology. The chip was designed on a a six-metal layer process - upper five layers can be used for global routing and M1 is reserved for local routing. The final microarchitecture had a total of 2,700,000 transistors consisting of 2,000,000 [[CMOS]] and 700,000 [[Bipolar]] transistors.

The on-die cache was made of a separate 2 kB [[L1$]] and a unified 32 kB [[L2$]]. The pipeline consisted of a shallow six-stage [[superscalar]] with [[in-order execution]]. At full throughput the design allows for a 3-way pipeline - capable of issuing 1 arithmetic (either integer or floating point, but not both), a single load/store operation, and a branch instruction.

== Die Shot ==
[[File:x704 floorplan.jpg|650px]]


[[File:bull fp.gif]]

== Documents ==

=== Manuals ===
* [[:File:X704 technical summary.pdf|X704 Technical Summary]], 1996

=== Papers ===
* C. A. Maier et al., "[http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=641683&isnumber=13972 A 533-MHz BiCMOS superscalar RISC microprocessor]," in IEEE Journal of Solid-State Circuits, vol. 32, no. 11, pp. 1625-1634, Nov 1997. doi: 10.1109/4.641683
designer	Exponential Technology +
first announced	October 21, 1996 +
full page name	exponential technology/x704 +
instance of	microprocessor family +
instruction set architecture	PowerPC +
main designer	Exponential Technology +
manufacturer	Hitachi +
microarchitecture	X704 +
name	X704 +
package	CBGA-359 +
process	500 nm (0.5 μm, 5.0e-4 mm) +
technology	BiCMOS +
word size	32 bit (4 octets, 8 nibbles) +