! Core !! Abbrev !! Target

| {{intel|Skylake Y|l=core}} || SKL-Y || 2-in-1s detachable, tablets, and computer sticks

| {{intel|Skylake U|l=core}} || SKL-U || Light notebooks, portable All-in-Ones (AiOs), Minis, and conference room

| {{intel|Skylake H|l=core}} || SKL-H || Ultimate mobile performance, mobile workstations

| {{intel|Skylake S|l=core}} || SKL-S || Desktop performance to value, AiOs, and minis

| {{intel|Skylake DT|l=core}} || SKL-DT || Workstations & entry-level servers

| style="background-color: #d6ffd8;" | Windows 7 || rowspan="2" | Support ends July 2017

**** Limits motherboard trace design to 7 inches max from (down from 8) from the CPU to chipset

** Intel Sensor Solution Hub integrationLarger Line Fill Buffer?

*** 1,152 GFLOPS @ 1 GHz

* Most ALU operations have 4 op/cycle 1 for 8 and 32-bit registers. 64-bit ops are still limited to 3 op/cycle. (16-bit throughput varies per op, can be 4, 3.5 or 2 op/cycle).

* MOVSX and MOVZX have 4 op/cycle throughput for 16->32 and 32->64 forms, in addition to Haswell's 8->32, 8->64 and 16->64 bit forms.

* ADC and SBB have throughput of 1 op/cycle, same as Haswell.

* Vector moves have throughput of 4 op/cycle (move elimination).

* Not only zeroing vector vpXORxx and vpSUBxx ops, but also vPCMPxxx on the same register, have throughput of 4 op/cycle.

* Vector ALU ops are often "standardized" to latency of 4. for example, vADDPS and vMULPS used to have L of 3 and 5, now both are 4.

* Fused multiply-add ops have latency of 4 and throughput of 0.5 op/cycle.

* Throughput of vADDps, vSUBps, vCMPps, vMAXps, their scalar and double analogs is increased to 2 op/cycle.

* Throughput of vPSLxx and vPSRxx with immediate (i.e. fixed vector shifts) is increased to 2 op/cycle.

**** 4 entries; fully associative

Accompanying the cores is the {{\\|Gen9}} [[integrated graphics]] unit which comes in a number of different tiers ranging from just 12 execution units (used in the ultra-low power models) all the way the GT4 ({{\\|gen9#Scalability|Gen9 § Pipeline}}) with 72 execution units boasting a peak performance of up to 2,534.4 GFLOPS (HF) / 1,267.2 GFLOPS (SP) on the highest-end workstation model. The two highest-tier models are also accompanied by dedicated [[eDRAM]] ranging from 64 GiB to 120 GiB in capacity. The eDRAM is packaged along with the SoC in the same package.

The front-end is is tasked with the challenge of fetching the complex [[x86]] instructions from memory, decoding them, and delivering them to the execution units. In other words, the front end needs to be able to consistently deliver enough [[µOPs]] from the instruction code stream to keep the back-end busy. When the back-end is not being fully utilized, the core is not reaching its full performance. A poorly or under-performing front-end will translate directly to a poorly performing core. This challenge is further complicated by various redirection such as branches and the complex nature of the [[x86]] instructions themselves.

On their first pass, instructions should have already been prefetched from the [[L2 cache]] and into the [[L1 cache]]. The L1 is a 32 [[KiB]], 8-way set associative cache, identical in size and organization to {{intel|microarchitectures|previous generations}}. Skylake fetching is done on a 16-byte fetch window. A window size that has not changed in a number of generations. Up to 16 bytes of code can be fetched each cycle. Note that fetcher is shared evenly between two thread, so that each thread gets every other cycle. At this point they are still [[macro-ops]] (i.e. variable-length [[x86]] architectural instruction). Instructions are brought into the pre-decode buffer for initial preparation.

[[x86]] instructions are complex, variable length, have inconsistent encoding, and may contain multiple operations. At the pre-decode buffer the instructions boundaries get detected and marked. This is a fairly difficult task because each instruction can vary from a single byte all the way up to fifteen. Moreover, determining the length requires inspecting a couple of bytes of the instruction. In addition boundary marking, prefixes are also decoded and checked for various properties such as branches. As with previous microarchitectures, the pre-decoder has a [[throughput]] of 6 [[macro-ops]] per cycle or until all 16 bytes are consumed, whichever happens first. Note that the predecoder will not load a new 16-byte block until the previous block has been fully exhausted. For example, suppose a new chunk was loaded, resulting in 7 instructions. In the first cycle, 6 instructions will be processed and a whole second cycle will be wasted for that last instruction. This will produce the much lower throughput of 3.5 instructions per cycle which is considerably less than optimal. Likewise, if the 16-byte block resulted in just 4 instructions with 1 byte of the 5th instruction received, the first 4 instructions will be processed in the first cycle and a second cycle will be required for the last instruction. This will produce an average throughput of 2.5 instructions per cycle. Note that there is a special case for {{x86|length-changing prefix}} (LCPs) which will incur additional pre-decoding costs. Real code is often less than 4 bytes which usually results in a good rate.  

The pre-decoded instructions are delivered to the Instruction Queue (IQ). In {{\\|Broadwell}}, the Instruction Queue has been increased to 25 entries duplicated over for each thread (i.e. 50 total entries). It's unclear if that has changed with Skylake. One key optimization the instruction queue does is [[macro-op fusion]]. Skylake can fuse two [[macro-ops]] into a single complex one in a number of cases. In cases where a {{x86|test}} or {{x86|compare}} instruction with a subsequent conditional jump is detected, it will be converted into a single compare-and-branch instruction. Those fused instructions remain fused throughout the entire pipeline and get executed as a single operation by the branch unit thereby saving bandwidth everywhere. Only one such fusion can be performed each cycle.

Up to five (3 + 2 fused or up to 4 unfused) pre-decoded instructions are sent to the decoders each cycle. Like the fetchers, the Decoders alternate between the two thread each cycle. Decoders read in [[macro-operations]] and emit regular, fixed length [[µOPs]]. Skylake represents a big genealogical change from the last couple of microarchitectures. Skylake's pipeline is wider than it predecessors; Skylake adds another [[simple decoder]]. The five decoders are asymmetric; the first one, Decoder 0,  is a [[complex decoder]] while the other four are [[simple decoders]]. A simple decoder is capable of translating instructions that emit a single fused-[[µOP]]. By contrast, a [[complex decoder]] can decode anywhere from one to four fused-µOPs. Skylake is now capable of decoding 5 macro-ops per cycle or 25% more than {{\\|Broadwell}}, however this does not translates directly to direct IPC uplift to due to various other more restricting points in the pipeline. Intel chose not increase the number of complex decoders because it's much harder to extract additional parallelism from the µOPs emitted by a complex instruction. Overall up to 5 simple instructions can be decoded each cycle with lesser amounts if the complex decoder needs to emit addition µOPs; i.e., for each additional µOP the complex decoder needs to emit, 1 less simple decoder can operate. In other words, for each additional µOP the complex decoder emits, one less decoder is active.

Like the front-end, the [[Reorder Buffer]] has been increased to 224 entries, 32 entries more than {{\\|Broadwell}}. It is at this stage that [[architectural registers]] are mapped onto the underlying [[physical registers]]. Other additional bookkeeping tasks are also done at this point such as allocating resources for stores, loads, and determining all possible scheduler ports. Register renaming is also controlled by the [[Register Alias Table]] (RAT) which is used to mark where the data we depend on is coming from (after that value, too, came from an instruction that has previously been renamed). In {{intel|microarchitectures|previous microarchitectures}}, the RAT could handle 4 µOPs each cycle. Intel has not disclosed if that has changed in Skylake but it's possible. If this has not change, Skylake can rename any four registers per cycle. This includes the same register renamed four times in a single cycle. If the rename has not increased in Skylake, some aspects of improvements that were done in the prefetch/decode stages are effectively lost. Note that the ROB still operates on fused µOPs, therefore 4 µOPs can effectively be as high as 8 µOPs.

The L2 to L1 bandwidth in Skylake is the same as {{\\|Haswell}} at 64 bytes per cycle in either direction. Note that one operation can be done each cycle; i.e., the L1 can either receive data from the L1 or send data to the Load/Store buffers each cycle, but not both. Latency from L2$ to L3$ has also been decreased from 4 cycles/line to 2 cycles/line. The bandwidth from the level 2 cache to the shared level 3 is 32 bytes per cycle.

The Skylake family consists out of  5 different actual dies. Witch can be further segmented by disabling different features, e.g. GT1 graphics are based on GT2 graphics with half the execution units disabled.

Information from the new domains, including additional thermal skin temperature control information is now supplied to OEMs.

Note that core ratio has been increased to a [theoretical] x83 multiplier and the coarse-grain ratio was dropped from Skylake allowing a BCLK ratio to have granularity of 1 MHz increments with BCLK frequency of over 200 readily achievable. The FIVER was removed and the voltage control was given back to the motherboard manufacturers; i.e., voltage supplies can be entirely motherboard-controlled. Skylake also bumped the DDR ratio up to 4133 MT/s.

* 13 [[megapixel|MP]] zero [[shutter lag]] 1080p60/2160p30 video capture and imaging and a large array of standardized image processing capabilities.  

| {{intel|HD Graphics 510}} || 12 || GT1 || {{intel|Skylake U|U|l=core}}, {{intel|Skylake S|S|l=core}} ||  - || rowspan="11" colspan="2" style="text-align: center;" | '''1.0''' || rowspan="11" style="text-align: center;" | '''12''' || rowspan="11" style="text-align: center;" | '''N/A''' || rowspan="11" style="text-align: center;" | '''5.1''' || rowspan="11" style="text-align: center;" | '''4.5''' || rowspan="11" style="text-align: center;" | '''4.5''' || rowspan="11" style="text-align: center;" colspan="2" | '''2.0'''

| [[File:skylake h (back).png|100px|link=intel/cores/skylake_h]] || {{intel|Skylake H|l=core}} || {{intel|BGA-1440}} || Yes || 2-chip || rowspan="2" | {{intel|Sunrise Point}} || rowspan="4" | [[DMI 3.0]]

Client models come in groups of 2 or 4 cores. (die sizes includes the dark silicon space where the L3 ends).

* ~8.91 mm x ~2.845 mm

* ~8.844 mm x 5.694 mm

* ~9.57 mm x ~10.3 mm

* ~98.57 mm² die size

: [[File:skylake (quad-core).png|650px]]