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Review: AMD Radeon RX 6700 XT

by Tarinder Sandhu on 17 March 2021, 13:01

Tags: AMD (NYSE:AMD)

Quick Link: HEXUS.net/qaeqbq

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Introduction

AMD introduced the Radeon RX 6700 XT 12GB graphics card a couple of weeks ago. Representing the fourth model in the RX 6000 Series based on the second-generation Navi architecture, AMD hopes to convince well-heeled enthusiasts to forget about the rival GeForce RTX 3070 and RTX 3060 Ti cards for their next upgrade and choose Team Red instead.

Radeon RX 6700 XT is officially priced from $479 (£419) but we expect stock constraint to be so huge that it is easy to disregard this headline figure. You'll do well to get one at all today, irrespective of cost, which is a testament to the wildly skewed demand vs. limited supply that's persisted for months.

As much as we can continue to lament availability and price gouging by retailers, RX 6700 XT is an important GPU because it establishes how AMD intends to fill the Navi 2x stack and compete with Nvidia's SRP-comparable boards.

Our usual method of implementation dissection occurs with perusal and analysis of the specifications through a generation-wide table. So here we go.

From Navi 1x to Navi 2x

 
Radeon RX 6900 XT
Radeon RX 6800 XT
Radeon RX 6800
Radeon RX 6700 XT
Radeon RX 5700 XT
Radeon RX 5700
Launch date
December 2020
November 2020
November 2020
March 2021
July 2019
July 2019
Codename
Navi 21
Navi 21
Navi 21
Navi 22
Navi 10
Navi 10
Architecture
RDNA 2
RDNA 2
RDNA 2
RDNA 2
RDNA
RDNA
Process (nm)
7
7
7
7
7
7
Transistors (bn)
26.8
26.8
26.8
17.2
10.3
10.3
Die Size (mm²)
519
519
519
336
251
251
Full Implementation of Die
Yes
No
No
Yes
Yes
No
Hardware Raytracing
Yes
Yes
Yes
Yes
No
No
Infinity Cache (MB)
128
128
128
96
No
No
Compute Units
80
72
60
40
40
36
Processors
5,120
4,608
3,840
2,560
2,560
2,304
Texture Units
320
288
240
160
160
144
ROP Units
128
128
96
64
64
64
Boost Clock (MHz)
2,250
2,250
2,105
2,581
1,905
1,725
Game Clock (MHz)
2,015
2,015
1,815
2,424
1,755
1,625
Peak GFLOPS (SP)
23,040
20,736
16,166
13,215
9,750
7,950
Memory Type
GDDR6
GDDR6
GDDR6
GDDR6
GDDR6
GDDR6
Memory Size (GB)
16
16
16
12
8
8
Memory Clock (MHz)
16,000
16,000
16,000
16,000
14,000
14,000
Memory Bus (bits)
256
256
256
192
256
256
Max Bandwidth (GB/s)
512
512
512
384
448
448
PCIe Support
Gen 4
Gen 4
Gen 4
Gen 4
Gen 4
Gen 4
Power Connectors
8+8
8+8
8+8
6+8
6+8
6+8
TDP (watts)
300
300
250
230
225
180
GFLOPS per watt
76.8
69.1
64.66
57.46
43.3
44.2
Launch MSRP
$999
$649
$579
$479
$399
$349

Radeon RX 6700 XT Analysis

The first point of note is that RX 6700 XT uses a smaller, distinct die than the Radeon RX 6800/XT/6900 XT trio. Those three share the largest implementation known as Navi 21 which encompasses 26.8bn transistors across 519mm². A big chip for big performance. RX 6700 XT, meanwhile, fits its performance chops into a die that's 17.2bn transistors and 336mm². Put simply, Navi 21 is more than 50 per cent larger on both counts.

Discussion of die size and related transistor budgets is not merely for the curious. Having a significantly smaller die ought to reduce the GPU cost considerably and, one would think, improving yield rates - and therefore production runs - from having to deal with fewer transistors.

Heck, the chop between Navi 21 and Navi 22 is rather stark and severe. AMD knows this and uses the full capability of the die, which translates to a 40-CU chip that keeps to the same building blocks of the present series. This means 64 cores, four texture-units, and one ray accelerator per CU. Other than the hardware-based ray tracing assistance, RX 6700 XT's top end is identical to RX 5700 XT, so it will be interesting to see how the improvements in second-generation Navi play out in the benchmarks.

AMD knows that by stifling key performance building blocks to this degree - RX 6800, for example, has 50 per cent more than RX 6700 XT - it needs to ramp up the frequency for the new card to be competitive. And so it does, right up to a Boost Clock of 2,581MHz, which is the highest we have ever seen from a gaming GPU. Cranking out the TFLOPs by going relatively narrow and fast shows the RX 6700 XT in a better light as it closes the throughput gap to RX 6800 by a reasonable degree.

Fitting everything into a smaller die means sacrifices elsewhere. On the back-end these materialise as a 192-bit bus feeding 64 ROPs, resulting in a potential 384GB/s of bandwidth from the external 12GB GDDR6 memory. AMD also cuts down on the Infinity Cache from Navi 21's 128MB to 96MB - operating at the same 1.94GHz speed but limited to 12 channels instead of 16 - which is a sensible move given the target QHD resolution in mind.

One would expect that such wholesale cuts to the Navi architecture would translate to a much more power-frugal card. That is not the case as RX 6700 XT is plumbed with a 230W TDP. AMD's need to increase the frequency wick and, one would assume, voltage helps explain the higher-than-expected figure. Of course, GPU designs are first sketched out years before. The final months are spent by the implementation team in ensuring the intended GPU is competitive. For RX 6700 XT and Navi 22, it can be argued AMD undershot the projected Nvidia performance, hence the super-high frequencies this time around.

It's tough to make accurate performance predictions based on the changes AMD has made from the high-performance Navi chips released in November and December last year. What's more important is that AMD is able to combat the GeForce RTX 3070 and RTX 3060 Ti threat. It may well do so in rasterisation titles, but if recent history is anything to go by, will struggle in ray tracing games. It's not lost on us that AMD, for now, has no answer to Nvidia's framerate-enhancing DLSS technology.

As of today, partners will retail a slew of Radeon RX 6700 XT cards based on in-house cooling. The Made By AMD (MBA) board, meanwhile, will be listed solely on AMD.com at the recommended price, though don't expect much in the way of quantity.

Writing of the reference board, let's take a closer look.