Xref: utzoo comp.sys.amiga:25978 comp.sys.amiga.tech:2646 Path: utzoo!utgpu!watmath!clyde!att!rutgers!gatech!purdue!decwrl!labrea!polya!rokicki From: rokicki@polya.Stanford.EDU (Tomas G. Rokicki) Newsgroups: comp.sys.amiga,comp.sys.amiga.tech Subject: Re: BLITTER-NASTY Keywords: BLITTER,NASTY,HOW Message-ID: <5433@polya.Stanford.EDU> Date: 2 Dec 88 22:49:08 GMT References: <143@sluga.UUCP> Reply-To: rokicki@polya.Stanford.EDU (Tomas G. Rokicki) Organization: Stanford University Lines: 28 Is it anyone out there who knows how the blitter nasty function works. Me and a friend are making some games for the amiga,but when we tried to speed up the games by turn on blitter nasty,we didn't see any change at all. Normally, the blitter runs essentially full-out, unless the processor has been blocked from a memory access for so many consecutive cycles (3?), in which case the processor is given a single cycle. The nasty mode just makes sure the processor doesn't even get these cycles. In the hardware manual it say's that if you turn on blitter nasty,the processor will have no(almost) time at all,and if that's true then we wouldn't have to do a Blitter-Ready-Loop before starting with the next bitplane. Not really true; many blitter functions (line draw and many `normal' blits) don't use all possible DMA cycles. Line draw, for instance, does a single read and a single write every four possible memory cycles. The processor could get in on the other cycles. A blitter-ready loop would only be unnecessary if the blitter were in a mode where all possible DMA cycles are taken (a three-source one-destination blit, for instance), blitter nasty was used, and the processor was doing fetches from CHIP RAM. In other words, almost never, and I would certainly never recommend it. -tom