AMOLED (active-matrix organic light-emitting diode) is a display technology for use in mobile devices and televisions. OLED describes a specific type of thin-film display technology in which organic compounds form the electroluminescent material, and active matrix refers to the technology behind the addressing of pixels.
As of 2012, AMOLED technology is used in mobile phones, media players and digital cameras, and continues to make progress toward low-power, low-cost and large-size (for example, 40-inch) applications

An AMOLED display consists of an active matrix of OLED pixels that generate light (luminescence) upon electrical activation that have been deposited or integrated onto a thin film transistor (TFT) array, which functions as a series of switches to control the current flowing to each individual pixel.^[
Typically, this continuous current flow is controlled by at least two TFTs at each pixel (to trigger the luminescence), with one TFT to start and stop the charging of a storage capacitor and the second to provide a voltage source at the level needed to create a constant current to the pixel, thereby eliminating the need for the very high currents required for passive matrix OLED operation.
TFT backplane technology is crucial in the fabrication of AMOLED displays. Two primary TFT backplane technologies, namely polycrystalline silicon (poly-Si) and amorphous silicon (a-Si), are used today in AMOLEDs. These technologies offer the potential for fabricating the active matrix backplanes at low temperatures (below 150°C) directly onto flexible plastic substrates for producing flexible AMOLED displays.

source - http://en.wikipedia.org/wiki/AMOLED

Retina Display is a brand name used by Apple for liquid crystal displays which they claim have a high enough pixel density that the human eye is unable to notice pixelation at a typical viewing distance. The term is used for several Apple products, including the iPhone, iPod Touch, iPad, and MacBook Pro. As the typical viewing distance would be different depending on each device's usage, the pixels per inch claimed as retina quality can be different for the smallest devices (326, iPhone and iPod Touch): greater than the mid-sized devices (264, iPad) and greater than the larger devices (220, MacBook Pro).
The displays are manufactured by different suppliers. Currently, the iPad's display comes from the same suppliers Samsung use while the Macbook Pro displays are mostly made by LG's suppliers, along with the iPhone and iPod Touch displays.^{[citation needed]} Apple has applied to register the term "Retina" as a trademark in regard to computers and mobile devices with the United States Patent and Trademark Office, Canadian Intellectual Property Office, and in Jamaica. On November 27, 2012 the US Patent and Trademark office approved Apple's application and Retina® is now a registered trademark.

Retina Display trigonometrical pixel density

Retina Display's real unit of measure is PPD: Pixels Per Degree. When introducing the iPhone 4, Steve Jobs said the magic number for a retina display is about 300 PPI for a device held 10 to 12 inches from the eye, which correlates to a PPD (at 10 inches) of 53. If a display's pixel density is more than 53 PPD (57 PPD for the iPhone 4 display) viewed from its optimal distance, that is a Retina Display. 53 PPD pixel density means that there are 53 pixels visible in one degree view angle. For example, 53 PPD means that when viewed from the expected distance, if an imaginary triangle is drawn between two chosen pixels and the eye of the viewer, with a one-degree angle formed at the vertex of the triangle that is at the viewer's eye, then there will be 53 pixels along the opposite side of the triangle (between the other two vertices of the triangle, which are at the chosen pixels). Any display's viewing quality (from phone displays to huge projectors) can be described with this size-independent universal parameter. Note that the PPD parameter is not an intrinsic parameter of the display itself, unlike absolute pixel resolution (e.g. 1024 x 800 pixels) or relative pixel density (e.g. 72 PPI), but is dependent on the distance between the display and the eye of the person (or lens of the device) viewing the display; moving the eye closer to the display reduces the PPD, and moving away from it increases the PPD in proportion to the distance. It can be calculated by multiplying the distance to the screen times the PPI resolution of the screen times π divided by 180 degrees.

source - http://en.wikipedia.org/wiki/Retina_Display

Windows Phone 8X by HTC

• Size: 132.35 x 66.2 x 10.12 mm
  
• Weight: 130 grams with battery
  
• Display: 4.3 inch touch screen with Gorilla® Glass 2
  
• Resolution: HD 720p
  

CPU Speed

Qualcomm® S4 1.5 GHz, Dual-core

Platform

Windows® Phone 8

SIM card type

MicroSIM

Memory¹

Total storage: 16 GB, available capacity varies
RAM: 1GB

Size (LxWxT)

132.35 x 66.2 x 10.12 mm

Display

4.3 inch super LCD 2 touch screen with HD 720p resolution
Gorilla® Glass 2

Network²

GSM/GPRS/EDGE: 850/900/1800/1900 MHz
HSPA/WCDMA: 850/900/1900/2100 MHz

GPS

Internal GPS antenna with GLONASS

Sensors

G-Sensor
Digital compass
Proximity sensor
Ambient light sensor

Connectivity³

3.5 mm stereo audio jack
NFC capable
Bluetooth® 3.1
Wi-Fi®: IEEE 802.11 a/b/g/n

Sound enhancement

Studio-quality sound with Beats Audio™ built in
Enjoy bigger sound and superior fidelity with exclusive built-in amp

Main Camera

8 megapixel camera with auto focus, LED flash, and BSI sensor (for better low-light captures)
F2.0 aperture and 28mm lens
1080p video recording
Dedicated HTC ImageChip

Front Camera

Capture more with the ultra-wide-angle front camera
2.1 megapixel front camera
1080p front camera video recording
F2.0 aperture
Dedicated HTC ImageChip

Multimedia

Audio supported formats:
    Playback:  .aac, .amr, .m4a, .mp3, .wav, .asf, .wma (verison 9 and 10)
    Recording:  .wav (w/OneNote)

Video supported formats:
    Playback:  .3gp, .3g2, .mp4, m4v, asf, .wmv (version 9 and 10)
    Recording:  .mp4

Battery⁴

Embedded & rechargeable Li-ion Polymer battery
Capacity:  1800 mAh

AC adapter

Voltage range/frequency:  100 ~ 240 V AC, 50/60 Hz
DC output:  5 V and 1 A

SAR Value

Head:0.586 W/Kg@1g
Body:0.322 W/Kg@1g


source - http://www.htc.com/in/smartphones/htc-wp-8x/#specs

HTC Windows Phone 8X is company's flagship Windows Phone 8 coming with a powerful spec sheet wrapped in a svelte 0.39" body in nice candy colors. The 8X by HTC sports a 4.3" LCD 2 HD screen, which, if the One X display is any indication, should be a sight to behold, and has the respectable 342ppi pixel desnity. It ups the WP ante with a modern 28mm dual-core 1.5GHz Snapdragon S4 chipset, 1GB of RAM and 16GB of internal memory, thus equating its specs with the fierce WP8 competition in the face of the Samsung ATIV S, or the innnovative Nokia Lumia 920, which, however, has a lot more going for it with the PureView camera. How does the HTC 8X intend to differentiate from those? Why, Beats Audio, of course. The prominent branding is featured proudly on the back of the phone, promising deep bass sound and clearer audio. "The Windows Phone 8X by HTC featuring Beats Audio also offers a unique audio amplifier powering the 3.5mm audio jack and the speaker, boosting the audio signal for even better sound no matter if you’re listening to music, playing a game or watching a video," says HTC. As for the sniping capabilities, we have an 8MP shooter on the rear with dedicated shutter key, equipped with HTC's exclusive ImageSense technology, which is essentially a proprietary ISP, allowing for some additional photo trickery, like ultra fast capture times, and continuous shot mode that takes multiple frames per second. It sports ultra wide f/2.0 aperture, just like on the Lumia 920. What's even more interesting, is that the 2MP front-facing shooter is with the same ultra wide 88 degree angle, "allowing up to four people and more to be captured at once", and can shoot 1080p video as well, which should make for some pretty clean and crowded Skype video calls.

Pros

• Dual core processor
• Very fast processor (1500 MHz)
• Lots of RAM (1024 MB RAM)
• Big display (4.30 inches)
• Extremely high pixel density screen, over 300ppi (342 ppi)
• High-resolution display (720 x 1280 pixels)
• High-resolution camera (8 megapixels)
• Fast mobile data support (4G)
• Global phone that can work on any GSM/UMTS network in the world
• Dual-mode CDMA/GSM phone
• NFC

Cons

• Lacks microSD slot for storage expansion