| Hardware and OS | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Operating system | Microsoft Windows Phone 8.1, upgradable to Microsoft Windows 10 | Android 8.1 (Oreo); ColorOS 5.1 |
| Processor | Quad-core 1.2 GHz Cortex-A7 | Octa-core 1.8 GHz Cortex-A53 |
| Chipset | Qualcomm MSM8926 Snapdragon 400 (28 nm) | Qualcomm SDM450 Snapdragon 450 (14 nm) |
| GPU | Adreno 305 | Adreno 506 |
| Internal memory | 8 GB, 1 GB RAM | 16 GB, 2 GB RAM |
| External memory | microSD, up to 256 GB (dedicated slot) | microSD, up to 256 GB (dedicated slot) |
| Display | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Type | IPS LCD | IPS LCD |
| Size | 5" inc | 6.2" inc |
| Resolution | 720 x 1280 px | 720 x 1520 px |
| Protection | Corning Gorilla Glass 3 | |
| Touchscreen | capacitive touchscreen | capacitive touchscreen |
| Screen-to-Body Ratio | 67.6% | 81.2% |
| Display area | 68.9 cm2 | 95.9 cm2 |
| Display aspect ratio | 16:9 (height:width) | 19:9 (height:width) |
| Pixel Density | 294 PPI | 271 PPI |
| Colors | 16M | 16M |
| Other | ClearBlack display | |
| Connectivity | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| 3G Network | | HSDPA 850 / 900 / 2100 |
| 2G Network | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 | GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2 |
| 4G Network | | LTE |
| Wi-Fi | Wi-Fi 802.11 b/g/n, DLNA, hotspot | Wi-Fi 802.11 b/g/n, WiFi Direct, hotspot |
| Network | GSM / HSPA | GSM / HSPA / LTE |
| SIM card | Dual SIM (Micro-SIM, dual stand-by) | Dual SIM (Nano-SIM, dual stand-by) |
| Bluetooth | 4.0, A2DP | 4.2, A2DP, LE |
| Edge | Yes | Yes |
| GPRS | Yes | Yes |
| GPS | Yes, with A-GPS, GLONASS, BDS | Yes, with A-GPS |
| Speed | HSPA 42.2/5.76 Mbps | HSPA 42.2/5.76 Mbps, LTE-A (2CA) Cat6 300/50 Mbps |
| USB | microUSB 2.0 | microUSB 2.0, USB On-The-Go |
| Camera | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Main camera | 8 MP, Single | 13 MP, Dual |
| Specs | 8 MP, f/2.2, 28mm (wide), 1/4', AF | 13 MP, f/2.2, AF
-2 MP, f/2.4, depth sensor |
| Features | LED flash | LED flash, HDR, panorama |
| Video | 1080p@30fps | 1080p@30fps |
| Selfie camera | 1 MP, Single | 8 MP, Single |
| Multimedia | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| 3.5 mm Jack | Yes | Yes |
| Radio | FM radio | FM radio |
| Design | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Colors | Glossy cyan, Orange, White, Matte black | Red, Dark Purple |
| Dimensions | 141.3 x 72.2 x 8.8 mm | 156.2 x 75.6 x 8.2 mm |
| Weight | 145 g | 168 g |
| Battery | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Battery capacity | 2500 mAh, Removable Li-Ion | 4230 mAh, Non-removable Li-Ion |
| Battery life | Stand by time- Up to 840 h (2G) / Up to 840 h (3G)
Talking time- Up to 27 h 30 min (2G) / Up to 20 h 30 min (3G)
| |
| Other | Microsoft Lumia 640 Dual SIM | Oppo A3s |
| Release date | 2015, March | 2018, July |
| Sensors | Accelerometer, proximity, compass | Accelerometer, proximity, compass |
