Why AMD’s RX 6500 XT is missing SO MUCH…
AMD launched a new GPU this week – no, sadly I don’t have one, but if the reviews are anything to go buy that doesn’t seem like such a bad thing. In fact, this 5 year old RX 580 – hell this 6 year old RX 480 both has more features, more VRAM and can even have more performance… So what the hell is AMD playing at? Well, let me explain.
First I should make it clear this video isn’t excusing AMD for the 6500 XT, nor any attempt to convince you to buy one, this is purely some context and explanations, and basically a look at what makes GPUs so damn expensive. So what do these cards have that the new $199 – sorry £250 – card doesn’t?
How about half the memory. Yeah, in 2022 AMD had the guts to sell a brand new, completely redesigned GPU with… 4GB of VRAM. 4GB! Back in 2017 when the RX 580 launched no one wanted the 4GB version of the 580, and that was FIVE YEARS AGO! Even AMD knew it wasn’t a good idea, as someone tried to quietly hide a blog post from 2020 about how 4GB of VRAM isn’t enough anymore, only to be caught, called on it and quietly reinstate it. (As an aside I wouldn’t attribute to malice what could be adequately described by incompetence, so ‘well-wishing moron hides blog post without thinking it through just hours before a launch’ makes much more sense than ‘multi-billion dollar company who has been designing a naff card for at least a year hurriedly, maliciously removes a contradicting blog post just hours before the launch instead of months before’, at least to me.)
Know what else is missing? Half the lanes to that memory too! This has a megre 64 bit bus, instead of the already fairly slim 128 bit bus the bigger Navi 23 (6600 and 6600 XT) has, which itself is only half of the 256 bit the Navi 21 (6900 XT, 6800 XT and 6800) has instead. While we are talking about halves, how about quarters? Like the PCIe lanes! Yeah! This card has just 4 PCIe lanes. Gen 4 lanes mind you, which of course will work great with.. Oh, just the last two generations of AMD or Intel CPUs. Hope you upgraded relatively recently!
That’s got to be it right? WRONG! It gets worse. Obviously you have less cores, but.. LITERALLY HALF? Just 1024 from just 16 compute units, compared to literally double that in the 6600 XT. Hell it has 50% less cores than the last generation 5500 XT, on top of half the memory and bus width. It also only has two display outputs from the GPU die, which, guess what? Is HALF of the last gen card.
But do you want to know what the real kicker of a missing feature is? It’s missing its video encoding engine. No more streaming for you! A feature present on a 5 year old card, or technically even an 8 year old card like this HD7870, but is missing in a card launched in 2022. What is going on?
Well, in short, it’s all about cost. Let’s start with the obvious one, the lack of memory. According to reports from mid last year, GDDR6 was set to skyrocket in price, and while this is definitely not even close to the prices AMD will be paying, nor is it the same SKU, Mouser has what I believe are 1GB GDDR6 modules listed for £22.50 a piece, which even with a hefty discount would clearly put a dent in the price tag having to put 8GB in instead of 4GB.
While the price of VRAM is an obvious place to look for AMD’s cost-cutting measures here, I’d argue it’s far from the biggest. See, by removing half the bus width, you now don’t need all those transistors to manage those inputs and process that data. By cutting the number of compute units in half you halve the number of transistors you need for the cores, removing the encoding engine will save plenty too, as will the display outputs. All of those transistors you suddenly don’t need to include add up – they add up to a chip that has less than half the area, just 107mm2, down from 237mm2 on the 6600 XT (although the much better equipped 5500 XT’s die area is 158mm2 AND on the in theory ‘larger’ 7 Nm process node rather than the newer 6500 XT on 6 Nm).
Ok, so you need fewer transistors, so what? Well those transistors have to come from somewhere, specifically specially doped silicon on what’s called a “wafer” – a perfectly doped and machined disc of silicon that through an insanely complicated collection of machines is turned into chips for you to have with your dinn.. No sorry GPUs to game on! Those wafers at 300mm in diameter, and a rough spitballing of the Navi 23 die plugged into a yield calculator with TSMC’s 7 Nm defect density of 0.09 nets you just shy of 200 good dies, and a further 45 defect dies. Defect dies aren’t necessarily dead, just not perfect so let’s assume some of them are fine and call it a nice round 200.
Now swap that to a rough spitball of the 6500 XT’s Navi 24 die and… 487! And 49 defect dies, so again a bit of rounding later and you get 500 6500 XT’s out of the same piece of silicon. That’s 150% more dies! That’s incredibly substantial. To give you some context, let’s imagine – and this is wholly imaginary based on no research or evidence – that a wafer costs say £5,000. Well, with 200 working 6600 and 6600 XT dies, that works out to around £25 per die. But with 500? That’s just £10 per die instead, and would be one hell of a saving!
When you tie that with the rising cost of those wafers – I’ve seen reports of 5-10% even for the 6/7Nm nodes at TSMC – and the likely case that AMD would have to pay a premium for more allocation than their multi-year agreement had listed, you then start to see why such a small die might have been necessary to get near this price point. Of course less I/O and memory also means the PCBs are cheaper and easier to produce and there are less components required which while that’s likely only pennies worth, it adds up.
But all that doesn’t mean you should buy one though. While it does seem like a good deal in today’s insane world of used RX 5500 XT’s (which were £200 new two years ago) listed for £400+, it’s important to see the bigger picture which is that you are getting less performance AND less features for the same or more money. And that’s one hell of a shame.
