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Review: NVIDIA GeForce GTX 650 Ti

by Tarinder Sandhu on 9 October 2012, 14:00 3.5

Tags: NVIDIA (NASDAQ:NVDA)

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Mainstream Kepler

The magic number is 120

The 'what-shall-I-buy' questions we're asked most often centre on the two pillars that make up the guts of a modern PC. Readers want to know which CPU and graphics card to buy for their next upgrade cycle. Our answer to these perennial questions depends upon users' budgets. Those strapped for cash would do well to take a look at AMD's all-in-one APUs, which offer basic CPU and GPU performance from a single-chip solution costing no more than £100.

Readers who've been beneficiaries of small windfalls from the passing of great-uncle George will doubtless specify an Intel Core i7-3960X CPU and a couple of NVIDIA GeForce GTX 690s, blowing a cool three grand on a trio of components. We believe that, more so than ever, spending £500 on a complete PC base unit will provide a solid user experience. Out of this arbitrary £500, we reckon it's sensible to allot no more than £150 each to the CPU and GPU.

Thinking about the add-in graphics, £120-£150 (or $150-$200) is enough to buy a card that can play the latest games at a full-HD, 1,920x1,080 resolution common on most computer monitors. Said card should also be able to run this resolution with console-beating graphics - usually translating to in-game options that include DX11 rendering and high-quality settings. AMD and NVIDIA, the two manufacturers of gaming cards, have always had strong representation in this mainstream segment; they follow the mass-market money.

Underscoring the above and as a long-winded but hopefully informative preamble, NVIDIA and its partners are launching a £120 graphics card that they hope will grab enthusiasts' attention. GeForce GTX 650 Ti is the name and low power and solid performance is the very much part of the game.

GeForce GTX 650 Ti?

Let's examine where this new GPU fits into a broad section of NVIDIA's mid-range GeForce hierarchy, including the GeForce GTX 550 Ti - the GPU effectively replaced by the card in for review today.

GPU GeForce GTX 660
(2,048MB)
GeForce GTX 650 Ti
(1,024MB)
GeForce GTX 550 Ti
(1,024MB)
Die codename Kepler GK106 Kepler GK106 Fermi GF116
DX API 11.1 11.1 11
Process 28nm 28nm 40nm
Transistors 2.54bn 2.54bn 1.17bn
Die Size 221mm² 221mm² 238mm²
SMX units 5 4 4
Processors 960 768 192
Texture Units 80 64 32
ROP Units 24 16 24
GPU Clock (MHz) 980 925 900
Shader Clock (MHz) 980 925 1,800
Boost Clock (MHz) 1,033 NA NA
GFLOPS 1,882 1,421 691
Memory Clock (MHz) 6,008 5,400 4,100
Memory Bus (bits) 192 128 192
Max bandwidth (GB/s) 144.2 86.4 98.5
Power Connectors 6-pin 6-pin 6-pin
TDP (watts) 140 105 115
GFLOPS per watt 13.44 13.53 6.01
Current MSRP £170 £120 £90

Analysis

A peek at the number of transistors for the GeForce GTX 660 and 650 Ti reveals that the duo are hewn from the same die. This means NVIDIA takes one common silicon and constructs at least two GeForces from it, and silicon that doesn't quite make the 'gold' GTX 660 grade is repurposed for use here. Note, however, that the next model up, GTX 660 Ti, uses the larger, more powerful GK104 die and the model further down, GTX 650, makes do with the slimline GK107.

The necessary cheapening of the GTX 660 occurs in a few obvious ways. First off, NVIDIA removes one of the SMX processing units. This has a two-fold effect: it reduces the total number of cores from 960 to 768 and, as they're tied to the SMXs, the texture-units fall from 80 to 64. There are further cuts to the back-end of the GPU, too, as ROPs are reduced from 24 to 16 and one of GTX 660's trio of 64-bit memory controllers gets the chop. The end result, as you can conclude, is comfortably lower computational throughput and a savage snip to memory bandwidth, which comes in at below GTX 550 Ti levels.

This liberal snipping is best illustrated by trotting out the block diagrams for the GTX 660 (top) and GTX 650 Ti (bottom). No expense has been spared (two minutes in Microsoft Paint) in showing you what's missing between the two GPUs. Out goes one SMX, one memory-controller partition and 128KB of L2 cache.

Referencing some of the numbers, GTX 660 has at least 30 per cent more GFLOPs throughput and 65 per cent extra memory bandwidth; the huge difference constituted by a wider memory bus and faster GDDR5 RAM. GTX 660, then, is in a different performance league, albeit based on the same die. What's more, GTX 650 Ti doesn't carry the GPU Boost ability of its bigger brother, where the card automatically clocks up if there's TDP scope to do so. And gamers may be disturbed to know that GTX 650 Ti doesn't support NVIDIA's SLI technology at all.

Reading the commentary so far suggests that GTX 650 Ti is a significantly poorer cousin in almost every way. But the real comparison is between NVIDIA's x50 Ti generations, and 650 Ti is better than 550 Ti in all performance parameters other than memory bandwidth.

GPU axe-happy NVIDIA has hamstrung the GK106 die to produce the GeForce GTX 650 Ti 1GB card, which, to be fair, is way better than the anaemic non-Ti variant. Priced at some £120 for vanilla cards, '650 Ti's biggest competitor is likely to be the Radeon HD 7770 1GB and, stretching the comparison elastic some, the Radeon HD 7850.

Summarising the above neatly, £120 remains a sensible amount of money to spend on a graphics card that should provide solid performance at 1,680x1,050 and 1,920x1,080 resolutions.