# Comparisons across microarchitectures

## Frontend

### Branch Prediction

| uArch | L1 BTB | L2 BTB | L3 BTB | ITA | RAS |
| :--- | :--- | :--- | :--- | ---: | :--- |
| AMD Zen 1 | 8 (0 bubble) | 256 (1 bubble) | 4096 (4 bubble) | 512 | 32 |
| AMD Zen 2 | 16 (0 bubble) | 512 (1 bubble) | 7168 (4 bubble) | 1024 | 32 |
| AMD Zen 3 | 1024 (0 bubble) | 6656 (3 bubble) |  | 1536 | 2x32 |
| AMD Zen 4 | 1536 (0 bubble) | 7168/7680 (3 bubble) |  | 3072 | 2x32 |
| AMD Zen 5 | 16384 (0 bubble) | 8192 (8 bubble) |  | 3072 | 2x52 |
| Ampere One | 256 (0 bubble) | 8192 (2 bubble) |  |  |  |
| Apple Avalanche | 1024 (0 bubble) | 3072 (1 bubble) | 192KB L1 IC (2 bubble) |  | 50 |
| Apple Firestorm | 1024 (0 bubble) | 192KB L1 IC (2 bubble) |  |  | 50 |
| Apple Icestorm |  |  |  |  | 32 |
| ARM Cortex-A77 | 64 (0 bubble) | 8192 |  |  |  |
| ARM Cortex-X1 | 96 (0 bubble) | 8192 (1 bubble) |  |  | 16 |
| ARM Neoverse-V1 |  |  |  |  |  |
| ARM Cortex-X2 |  |  |  |  | 16 |
| ARM Neoverse-N2 |  |  |  |  |  |
| ARM Cortex-X3 |  |  |  |  | 32 |
| ARM Neoverse-V2 |  |  |  |  |  |
| ARM Cortex-X4 |  |  |  |  | 32 |
| ARM Neoverse-V3 |  |  |  |  |  |
| ARM Cortex-A720 |  |  |  |  |  |
| ARM Neoverse-N3 |  |  |  |  |  |
| ARM Cortex-X925 |  |  |  |  | 32 |
| ARM C1-Pro |  |  |  |  |  |
| Intel Crestmont | 1024 (0 bubble) | 6144 (2 bubble) |  |  |  |
| Intel Golden Cove | 128 (0 bubble) | 6144 (1 bubble) | 12288 (2 bubble) |  | 20 |
| Intel Gracemont | 1024 (0 bubble) | 5120 (2 bubble) |  |  |  |
| Intel Lion Cove |  |  |  |  |  |
| Intel Redwood Cove | 128 (0 bubble) | 2x6144 (1 bubble) |  |  |  |
| Intel Skymont |  |  |  |  |  |
| Intel Sunny Cove | 256 (0 bubble) | 5120 (1 bubble) |  |  | 22 |
| Qualcomm Oryon | 2048 (0 bubble) | 192KB L1 IC (2 bubble) |  |  | 50 |

### L1 ICache + ITLB

| uArch | L1 IC | L1 ITLB | L2 ITLB |
| :--- | :--- | ---: | ---: |
| AMD Zen 1 | 4-way 64KB | 64 | 512 |
| AMD Zen 2 | 8-way 32KB | 64 | 512 |
| AMD Zen 3 | 8-way 32KB | 64 | 512 |
| AMD Zen 4 | 8-way 32KB | 64 | 512 |
| AMD Zen 5 | 8-way 32KB | 64 | 2048 |
| Ampere One | 4-way 16KB | 64 | 768 |
| Apple Avalanche | 192KB | 192 |  |
| Apple Firestorm | 6-way 192KB | 192 |  |
| Apple Icestorm | 128KB | 128 |  |
| ARM Cortex-A77 | 4-way 64KB | 48 |  |
| ARM Cortex-X1 | 4-way 64KB | 48 |  |
| ARM Neoverse-V1 |  |  |  |
| ARM Cortex-X2 | 4-way 64KB | 48 |  |
| ARM Neoverse-N2 |  |  |  |
| ARM Cortex-X3 | 4-way 64KB | 48 |  |
| ARM Neoverse-V2 |  |  |  |
| ARM Cortex-X4 | 4-way 64KB | 48 |  |
| ARM Neoverse-V3 |  |  |  |
| ARM Cortex-A720 |  |  |  |
| ARM Neoverse-N3 |  |  |  |
| ARM Cortex-X925 | 4-way 64KB | 128 |  |
| ARM C1-Pro | 4-way 64KB | 128 |  |
| Intel Crestmont | 8-way 64KB | 64 |  |
| Intel Golden Cove | 8-way 32KB | 256 |  |
| Intel Gracemont | 8-way 64KB | 64 |  |
| Intel Lion Cove |  |  |  |
| Intel Redwood Cove | 64KB |  |  |
| Intel Skymont | 64KB | 128 |  |
| Intel Sunny Cove | 8-way 32KB | 128 |  |
| Qualcomm Oryon | 6-way 192KB | 256 |  |

### Move Elimination / Zeroing Idiom / Ones Idiom

| Pattern\\uArch | Oryon | Firestorm | Golden Cove | Cortex X1 | Zen 3 | Sunny Cove | Zen 1-2 |
| --- | --- | --- | --- | --- | --- | --- | --- |
| \# ALU | 6 | 6 | 5 | 4 | 4 | 4 | 4 |
| \# Dispatch | 8 | 8 | 6 | 8 | 6 | 5 | 5 |
| Dep int add | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
| Indep int add | 6.0 | 3.9 | 4.7 | 4.0 | 4.0 | 4.0 | 4.0 |
| Dep int mov | 1.2 | 1.2 | **5.5** | 1.3 | **6.0** | **4.6** | **5.0** |
| Indep int mov | **8.0** | **8.0** | **5.4** | 4.0 | **6.0** | **4.6** | **5.0** |
| Dep zero via xor | 1.0 | 1.0 | **5.5** | 1.0 | **6.0** | **4.6** | *4.0* |
| Dep zero via sub | 1.0 | 1.0 | **6.0** | 1.0 | **6.0** | **4.6** | *4.0* |
| Indep set zero via mov | 6.0 | **8.0** | **6.0** | **6.0** | 4.0 | 3.7 | 4.0 |
| Indep set one via mov | 6.0 | **7.8** | **6.0** | 4.0 | 4.0 | 4.0 | 4.0 |
| Indep set two via mov | 6.0 | **7.8** | **6.0** | 4.0 | 4.0 | 4.0 | 4.0 |
| Indep set 1024 via mov | 6.0 | **7.8** | 5.0 | 4.0 | 4.0 | 4.0 | 4.0 |
| Vec dep mov | 0.6 | 0.6 | **6.0** | 0.5 | **6.0** | 1.0 | 4.0 |
| Vec indep mov | **8.0** | **8.0** | **6.0** | 4.0 | **6.0** | 3.0 | 4.0 |
| Vec dep set zero via xor | 0.5 | 0.5 | **6.0** | 0.5 | *4.0* | **5.0** | *4.0* |
| Vec dep set zero via sub | 0.5 | 0.5 | 0.5 | 0.5 | 0.3 | 0.25 | 0.3 |
| Vec indep set zero via mov | 4.0 | **8.0** | N/A | **6.0** | N/A | N/A | N/A |
| Nop | **8.0** | **8.0** | **5.7** | **8.0** | **6.0** | 4.0 | **5.0** |

- **Bold**: Not executed by ALU/FPU, eliminated at rename stage
- *Italics*: Executed by ALU/FPU, but source register dependency was removed so that dependent ops can be executed in parallel
- Although Cortex-X1 has 8 dispatch width, but it has many limitations on instruction type

## Backend

### ROB

| uArch | ROB |
| :--- | :--- |
| AMD Zen 1 | 192 |
| AMD Zen 2 | 224 |
| AMD Zen 3 | 256 |
| AMD Zen 4 | 320 |
| AMD Zen 5 | 448 |
| Ampere One | 208 |
| Apple Avalanche | 274 Group |
| Apple Firestorm | 330 Group |
| Apple Icestorm | nan |
| ARM Cortex-A77 | 160 MOP |
| ARM Cortex-X1 | 224 MOP |
| ARM Neoverse-V1 | nan |
| ARM Cortex-X2 | 288 MOP |
| ARM Neoverse-N2 | nan |
| ARM Cortex-X3 | 320 MOP |
| ARM Neoverse-V2 | nan |
| ARM Cortex-X4 | 384 MOP |
| ARM Neoverse-V3 | nan |
| ARM Cortex-A720 | nan |
| ARM Neoverse-N3 | nan |
| ARM Cortex-X925 | 768 MOP |
| ARM C1-Pro | 1024 MOP |
| Intel Crestmont | 256 |
| Intel Golden Cove | 512 |
| Intel Gracemont | 256 |
| Intel Lion Cove | 576 |
| Intel Redwood Cove | 512 |
| Intel Skymont | 416 |
| Intel Sunny Cove | 352 |
| Qualcomm Oryon | 680 |

### LSU

| uArch | 64b Load | 64b Store | 128b Load | 128b Store | 256b Load | 256b Store |
| --- | --- | --- | --- | --- | --- | --- |
| Zen2 | 2/cycle | 1/cycle | 2/cycle | 1/cycle | 2/cycle | 1/cycle |
| Zen4 | 3/cycle | 2/cycle | 2/cycle | 1/cycle | 2/cycle | 1/cycle |
| Golden Cove | 3/cycle | 2/cycle | 3/cycle | 2/cycle | 3/cycle | 2/cycle |
| Firestorm | 3/cycle | 2/cycle | 3/cycle | 2/cycle | 1.5/cycle | 1/cycle |
| Oryon | 4/cycle | 2/cycle | 4/cycle | 2/cycle | 2/cycle | 1/cycle |

### Execution Unit

| uArch | ALU units | Branch units | FP/Vec units |
| :--- | ---: | ---: | :--- |
| AMD Zen 1 | 4 | 2 | 4x 128b |
| AMD Zen 2 | 4 | 2 | 4x 256b |
| AMD Zen 3 | 4 | 2 | 4x 256b |
| AMD Zen 4 | 4 | 2 | 4x 256b |
| AMD Zen 5 | 6 | 3 | 4x 512b |
| Ampere One | 4 | 2 | 2 |
| Apple Avalanche | 6 | 2 | 4x 128b |
| Apple Firestorm | 6 | 2 | 4x 128b |
| Apple Icestorm | 4 | 2 | 2x 128b |
| ARM Cortex-A77 | 4 | 2 | 2 |
| ARM Cortex-X1 | 4 | 2 | 4 |
| ARM Neoverse-V1 | 4 | 2 | 4x 128b |
| ARM Cortex-X2 | 4 | 2 | 4x 128b |
| ARM Neoverse-N2 | 4 | 2 | 2x 128b |
| ARM Cortex-X3 | 6 | 2 | 4x 128b |
| ARM Neoverse-V2 | 6 | 2 | 4x 128b |
| ARM Cortex-X4 | 8 | 3 | 4 |
| ARM Neoverse-V3 | 8 | 3 | 4x 128b |
| ARM Cortex-A720 | 4 | 2 | 2x 128b |
| ARM Neoverse-N3 | 4 | 2 | 2x 128b |
| ARM Cortex-X925 | 8 | 3 | 6x 128b |
| ARM C1-Pro | 4 | 2 | 2 |
| Intel Crestmont | 4 | 2 | 3 |
| Intel Golden Cove | 5 | 2 | 3 |
| Intel Gracemont | 4 | 2 | 3x 128b |
| Intel Lion Cove | 6 | 3 | 4x 256b |
| Intel Redwood Cove | 5 | 2 | 3x 256b |
| Intel Skymont | 8 | 3 | 4x 128b |
| Intel Sunny Cove | 4 | 2 | 2x 512b |
| Qualcomm Oryon | 6 | 2 | 4x 128b |

## Comparison between microarchitectures

### Firestorm vs Oryon

|  | Apple Firestorm | Qualcomm Oryon |
| :--- | :--- | :--- |
| L1 BTB | 1024 (0 bubble) | 2048 (0 bubble) |
| L2 BTB | 192KB L1 IC (2 bubble) | 192KB L1 IC (2 bubble) |
| RAS | 50 | 50 |
| L1 IC | 6-way 192KB | 6-way 192KB |
| Decode width | 8 | 8 |
| Rename width | 8 | 8 |
| ROB | 330 Group | 680 |
| Branch units | 2 | 2 |
| ALU units | 6 | 6 |
| FP/Vec units | 4x 128b | 4x 128b |
| Load/Store pipes | 1 | 2 |
| Load-only pipes | 2 | 2 |
| Store-only pipes | 1 | 0 |

### Cortex-X series

|  | Cortex-X1 | Cortex-X2 | Cortex-X3 | Cortex-X4 | Cortex-X925 |
| :--- | :--- | :--- | :--- | :--- | :--- |
| ALU units | 4 | 4 | 6 | 8 | 8 |
| Branch units | 2 | 2 | 2 | 3 | 3 |
| Load/Store pipes | 2 | 2 | 2 | 1 | 2 |
| Load-only pipes | 1 | 1 | 1 | 2 | 2 |
| Store-only pipes | 0 | 0 | 0 | 1 | 0 |
| ROB | 224 MOP | 288 MOP | 320 MOP | 384 MOP | 768 MOP |
| Decode width | 5 | 5 | 6 | 10 | 10 |
| Rename width | 8 | 8 | 8 | 10 | 10 |
| Max Load | 3 | 3 | 3 | 3 | 4 |
| Max Store | 2 | 2 | 2 | 2 | 2 |
| Max Load+Store | 3 | 3 | 3 | 4 | 4 |