Silicon Investor (SI) -- The First Internet Community

STOCKTALK

We've detected that you're using an ad content blocking browser plug-in or feature. Ads provide a critical source of revenue to the continued operation of Silicon Investor. We ask that you disable ad blocking while on Silicon Investor in the best interests of our community. If you are not using an ad blocker but are still receiving this message, make sure your browser's tracking protection is set to the 'standard' level.

Technology Stocks : 3DFX -- Ignore unavailable to you. Want to Upgrade?

To: Plaz who wrote (12909)	5/21/1999 11:41:00 PM
From: bruce rogers	Read Replies (2) \| Respond to of 16960

Just a quick note that the 48000 MB/sec is probably quoted for the internal framebuffer bandwidth (on chip DRAM) for the PS2. I think the new Rambus chips run 16 bits per channel, so it's more like 3200 MB/sec for Rambus at 800 mhz x 2.

To: Plaz who wrote (12909)	5/23/1999 9:12:00 AM
From: SBHX	Read Replies (1) \| Respond to of 16960

AGP-4X shines as incremental Bandwidth gain. If you think of it as another channel of memory, then it is clear that it does add to the total available memory bw on the chip. In 3D rendereing, there are three main clients of memory : the destination color, Z and textures. Because you read and write Z, the BW required for Z is actually quite high, hence it is best on the primary memory, but texture coming from AGP helps when done correctly. IE: if you can bury the latency of the AGPread in the render pipeline, then the gain is significant. As for contention with CPU, don't forget that CPUs nowadays have really big caches, in many mips-intensive operations (eg : T&L), there are ways to structure the ops so that cache misses (one way is to do T&L in place per vertex instead of all T and then all L) are rare and actual memory access is low. Hence, even although that 100MHz 64bit memory looks weak, traffic across the hostbus from memory is very peaky and bursty, but overall, light. Just look at the bandwidth: PCI 33MHz * 32 bit bus / 8 bits/byte = 132 MB/sec AGP 66MHz * 32 bit bus / 8 bits/byte = 264 MB/sec AGP2x 66MHz * 32 bit bus / 8 bits/byte * 2 trans/clock = 528 MB/sec AGP4x 66MHz * 32 bit bus / 8 bits/byte * 4 trans/clock = 1056 MB/sec Voodoo3 3500 183Mhz * 128 bit bus / 8 bits/byte = 2928 MB/sec Sony PS2 2 channel 800MHz Rambus = 48000 MB/sec (published spec)