NVIDIA GeForce RTX 3080 10 GB “Ampere” Graphics Card Review

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PRODUCT INFO

NVIDIA GeForce RTX 3080

October, 2020
Type Graphics Card
Price $699.99 US

NVIDIA Ampere GPU - GDDR6X Memory Subsystem Deep Dive

The Micron GDDR6X memory brings a lot of new stuff to the table. It is faster, doubles the I/O data rate, and is the first to implement PAM4 multi-level signaling in memory dies. With the Geforce RTX 3090 class products, Micron's GDDR6X memory achieves a bandwidth of up to 1 TB/s which is used to power the next-generation gaming experiences at high-fidelity resolutions such as 8K.

Micron GDDR6X graphics memory doubles input/output (I/O) performance while minimizing the cost of memory. Working with AI-innovation leader NVIDIA, Micron delivers higher bandwidth by enabling multi-level signaling in the form of four-level pulse amplitude modulation (PAM4) technology in this memory device via Micron

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The new GDDR6X SGRAM:

  • Doubles the data rate of SGRAM at a lower power per transaction while enabling breaking of the 1 Terabyte per second (TB/s) system memory bandwidth boundary for graphics card applications;
  • Is the first discrete graphics memory device that employs PAM4 encoded signaling between the processor and the DRAM, using four voltage levels to encode and transfer two bits of data per interface clock.
  • Can be designed and operated stably at high speeds, and built-in mass-production.

As mentioned, GDDR6X features the brand new PAM4 multilevel signaling techniques which helps transfer data much faster, doubles the I/O rate, pushing the capability of each memory dies from 64 GB/s to 84 GB/s. The Micron GDDR6X memory dies are also the only graphics DRAM that can be mass-produced while feature PAM4 signaling.

What is interesting is that Micron quotes that its GDDR6X memory can hit speeds of up to 21 Gbps whereas we have only got to see 19.5 Gbps in action on the GeForce RTX 3090. It is likely that AIBs could utilize higher binned dies as they are available. Micron also confirms that they plan to offer speeds higher than 21 GB/s moving in 2021 but we will have to wait and see whether any cards will utilize them.

It's not just faster speeds but Micron's GDDR6X provides higher bandwidth while sipping in 15% lower power per transferred bit compared to the previous generation GDDR6 memory. PAM4 signaling is a big upgrade from the two-level NRZ signaling on the GDDR6 memory.

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Instead of transmitting two binary bits of data each clock cycle (one bit on the rising edge and one bit on the falling edge of the clock), PAM4 sends two bits each clock edge, encoded using four different voltage levels. The voltage levels are divided into 250 mV steps with each level representing two bits of data - 00, 01, 10, or 11 sent on each clock edge (still DDR technology).

Micron GDDR6X Memory

FeatureGDDR5GDDR5XGDDR6GDDR6X
DensityFrom 512Mb to 8Gb8Gb8Gb, 16Gb8Gb, 16Gb
VDD and VDDQEither 1.5V or 1.35V1.35VEither 1.35V or 1.25VEither 1.35V or 1.25V
VPPN/A1.8V1.8V1.8V
Data ratesUp to 8 Gb/sUp to 12Gb/sUp to 16 Gb/s19 Gb/s, 21 Gb/s,
>21 Gb/s
Channel count1122
Access granularity32 bytes64 bytes
2x 32 bytes in pseudo 32B mode
2 ch x 32 bytes2 ch x 32 bytes
Burst length816 / 8168 in PAM4 mode
16 in RDQS mode
SignalingPOD15/POD135POD135POD135/POD125PAM4 POD135/POD125
PackageBGA-170
14mm x 12mm 0.8mm ball pitch
BGA-190
14mm x 12mm 0.65mm ball pitch
BGA-180
14mm x 12mm 0.75mm ball pitch
BGA-180
14mm x 12mm 0.75mm ball pitch
I/O widthx32/x16x32/x162 ch x16/x82 ch x16/x8
Signal count61
- 40 DQ, DBI, EDC
- 15 CA
- 6 CK, WCK
61
- 40 DQ, DBI, EDC
- 15 CA
- 6 CK, WCK
70 or 74
- 40 DQ, DBI, EDC
- 24 CA
- 6 or 10 CK, WCK
70 or 74
- 40 DQ, DBI, EDC
- 24 CA
- 6 or 10 CK, WCK
PLL, DCCPLLPLLPLL, DCCDCC
CRCCRC-8CRC-82x CRC-82x CRC-8
VREFDExternal or internal per 2 bytesInternal per byteInternal per pinInternal per pin
3 sub-receivers per pin
EqualizationN/ARX/TXRX/TXRX/TX
VREFCExternalExternal or InternalExternal or InternalExternal or Internal
Self refresh (SRF)Yes
Temp. Controlled SRF
Yes
Temp. Controlled SRF Hibernate SRF
Yes
Temp. Controlled SRF Hibernate SRF
VDDQ-off
Yes
Temp. Controlled SRF Hibernate SRF
VDDQ-off
ScanSENIEEE 1149.1 (JTAG)IEEE 1149.1 (JTAG)IEEE 1149.1 (JTAG)
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