More AMD RV770 / Radeon HD 4850/4870 details


AMD R700

Apparently the official NDA on RV770 / 4800 series expires in less
than 2 hours as of this posting. That said, I found some interesting
info posted on Beyond3D:


* FP16 filtering is half speed, and the samplers are limited by
available interpolators (only 32 texcoords/clk) when processing INT8
at full speed
* 260mm2, 960M transistors or so
* Huge focus on area efficiency and perf/watt
* Chip was pad limited in the beginning***, so the last couple of
SIMDs are value adds that weren't originally planned for. Explains the
first point a little bit.
* ROPs are mostly 2x everywhere measured with MSAA and really help
the chip go fast. ROP MSAA downfilter this time.
* Seems to be 64KiB L1 per sampler with huge L1 bandwidth, new
* Finding peak rates everywhere on the chip has been easy. I've
seen 1Tflop FP32, full bilinear rates and peak INT8 blend and Z-only
writes (64 Zs/clock, yay!)
* GDDR5 is really what lets the chip kick some real ass
* GS perf is up compared to RV670, maybe a new (bigger) coalescing
stream out cache there, and more threads in flight
* Colour cache is per ROP, same as R6
* 16KiB per SIMD shared memory + 16KiB global (not the SMX)
* All 800 SPs can do integer, fat one only for specials still. 1
FP32 MAD or 1 FP<->INT or 1 integer op/clock for all
* New caching scheme for the RF I think
* Orlando-led design but very distributed in terms of teams. Scott
Hartog led, and he worked on i740 at Intel
* Over 5MiB of SRAM on-chip if you count every pool
* New UVD block with 7.1 over HDMI
* No ring bus MC, new controller nice and efficient due to new ROP

"It's the single most impressive graphics processor (and pairing with
a memory technology, nice one Joe!) I've ever seen, when looked at as
a whole. I don't say that lightly either, there have been some winning
chips over the years.

Deeply impressive and really deserves to get ATI back on the map when
it comes to performance 3D graphics. Sorry I won't have anything more
filling for arch NDA expiry, go read, Tech Report and
Morgoth's pieces if you want more data."


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