RX7600 and RX7600XT have 8GB or 16GB attached to a 128-bit bus.
RX7900XT and W7900 have 24GB or 48GB attached to a 384-bit bus.
Neither upgrade changes the bus width, only the memory chips.
The two upgraded models even use the same memory chips, as far as I can tell! GDDR6, 18000MT/s, 2GB per 16 pins. I couldn't confirm chip count on the W7900 but it's the same density.
Perhaps I should have been clearer and said "if you want more memory than the 16GB model you need a wider bus" but this confirms what I described above.
- cheap gfx die with a 128-bit memory interface.
- vastly more expensive gfx die with a 384-bit memory interface.
Essentially there's a cheap upgrade option available for each die, swapping the 1GB memory chips for 2GB memory chips (GDDR doesn't support a mix). If you have the 16GB model and you want more memory, there are no bigger memory chips available, and so you need a wider bus and that's going to cost significantly more to produce and hence they charge more.
As a side note, I would expect the the GDDR chips to be x32, rather than 16.
> Essentially there's a cheap upgrade option available for each die
Hmm, I think you missed what my actual point was.
You can buy a card with the cheap die for $270.
You can buy a card with the expensive die for $1000.
So far, so good.
The cost of just the memory upgrade for the cheap die is $60.
The cost of just the memory upgrade for the expensive die is $3000.
None of that $3000 is going toward upgrading the bus width. Maybe one percent of it goes toward upgrading the circuit board. It's a huge market segmentation fee.
> As a side note, I would expect the the GDDR chips to be x32, rather than 16.
The pictures I've found show the 7600 using 4 ram chips and the 7600 XT using 8 ram chips.
I did miss your point, I misunderstood the hefty price tag was just for the memory. Thank you for not biting my head off! That is pretty mad. I'm struggling to think of any explanation other than yours. Even a few supporting upgrades maybe required for the extra memory (power supplies etc) wouldn't be anywhere near that cost.
Of course - clamshell mode! They don't connect half the data bus from each chip. Also explains how they fit it on the card so easily without (and cheeply).
Yeah, though a way to connect fewer data pins to each chip doesn't particularly have to be clamshell, it just requires a little bit of flexibility in the design.
RX7600 and RX7600XT have 8GB or 16GB attached to a 128-bit bus.
RX7900XT and W7900 have 24GB or 48GB attached to a 384-bit bus.
Neither upgrade changes the bus width, only the memory chips.
The two upgraded models even use the same memory chips, as far as I can tell! GDDR6, 18000MT/s, 2GB per 16 pins. I couldn't confirm chip count on the W7900 but it's the same density.