A Linux update may have let slip AMD Big Navi's mammoth core specs

The Radeon RX 6000 looks like it could live up to the hype. — (Image credit: AMD)

The summer of leaks continues, this time with the attention turning to AMD's next-gen GPUs based on the RDNA 2 architecture, which we'll find out more about on October 28. An enterprising redditor (via Tom's Hardware) was digging around the Radeon Open Compute (ROCm) code and discovered what appears to be a specification list for two of AMD's next generation GPUs.

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GPU specification from the Linux Kernal Update
Parameter	Sienna Cichlid	Navy Flounder
gc_num_se	4	2
gc_num_cu_per_sh	10	10
gc_num_sh_per_se	2	2
gc_num_rb_per_se	4	4
gc_num_tccs	16	12
gc_num_gprs	1024	1024
gc_num_max_gs_thds	32	32
gc_gs_table_depth	32	32
gc_gsprim_buff_depth	1792	1792
gc_double_offchip_lds_buffer	1024	1024
gc_wave_size	32	32
gc_max_waves_per_simd	16	16
gc_lds_size	64	64
num_sc_per_sh	1	1
num_packer_per_sc	4	4

Details for two GPUs codenamed Sienna Cichlid (Navi 21, or Big Navi) and Navy Flounder (Navi 22 or 23) were revealed. Of most interest here is the fact that Big Navi does appear to confirm the rumours that it will be a 80 CU (Compute Unit) chip, while Navy Flounder appears to have 40 CUs. Multiply the top three numbers in the table to get the CU count. According to the document Big Navi will have a 256-bit memory bus, while Navy Flounder appears to have a 192-bit memory bus.

It's too early to say how these numbers relate to performance, or whether they're even accurate, but the general rumours are that Big Navi shouldn't be far off the performance of the Nvidia RTX 3080. If true that could make for some seriously interesting competition—something we haven't had for a few years now. We'll have to wait and see.

As for Navy Flounder, it appears to be a replacement of the Radeon RX 5700 XT, but using the newer RDNA 2 architecture, which supports real time ray tracing among other goodies. Obviously we have no indication of performance or pricing yet, but hopefully AMD can keep Nvidia honest all the way through the stack.

AMD still has just over a month to go before these cards are officially announced, but we'd have to assume that the underlying hardware won't change at this point—there simply isn't enough time to do so. Even so, you should still take these specs with a pinch of salt, as they aren't official, even if they appear to come from a legitimate source.

Alan has been writing about PC tech since before 3D graphics cards existed, and still vividly recalls having to fight with MS-DOS just to get games to load. He fondly remembers the killer combo of a Matrox Millenium and 3dfx Voodoo, and seeing Lara Croft in 3D for the first time. He's very glad hardware has advanced as much as it has though, and is particularly happy when putting the latest M.2 NVMe SSDs, AMD processors, and laptops through their paces. He has a long-lasting Magic: The Gathering obsession but limits this to MTG Arena these days.