On Thu, 25 Dec 2003 20:00:48 -0800 (PST), Alex Deucher wrote: >--- Felix Khling <[EMAIL PROTECTED]> wrote: >> Alex Deucher <[EMAIL PROTECTED]> wrote: >> >> After a brief look at the utah driver: the S3 driver is definitely >> not >> based on the utah-driver. They are completely different. However, the >> register defines look very similar. There is also a BCI and the >> primitive types and vertex formats are encoded in the same way. I >> havn't >> checked the 3D state registers in detail. The savage4 driver uses DMA >> buffers to transfer commands, the savage IX driver uses the BCI. I >> don't >> know if the savage IX didn't have busmaster DMA capabilities, at >> least >> the relevant register defines are missing in the utah driver. > >Tim, I don't suppose you could help clarify the situation with savage3D >vs savage4 when it comes to DMA/BCI? I thought the BCI was a command >processor like the CP on r128/radeon/r200, but it's been a while since >I messed with the savage driver.
All of the Savage/ProSavage/SuperSavage chips support both BCI-through-FIFO and BCI-through-DMA. S3's Windows drivers use the DMA path exclusively, because there is a bug in the Savage4 engine (which is also in the ProSavages) that causes about 10% of the chips to lock up when reading the FIFO status register. This is the "scrolling hang" referred to on my web site. (You would think that simulations would have uncovered a problem in the single most important register in the entire chip, but I digress...) I assume the Savage/IX driver uses BCI-through-FIFO because it avoids the need for DMA kernel assistance, but the Savage4 scheme should work there just as well. If there is a strong desire, I could scan through the documents and see if any of the DMA registers have different addresses, but when I was working on the Savage Windows NT drivers, I did some experiments and learned that DMA only bought about 10% additional performance. -- - Tim Roberts, [EMAIL PROTECTED] Providenza & Boekelheide, Inc. ------------------------------------------------------- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id78&alloc_id371&op=click -- _______________________________________________ Dri-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/dri-devel
