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Received: by minnie.vk1xwt.ampr.org with NNTP id AA5553 ; Fri, 01 Jan 93 01:48:52 EST Xref: sserve comp.unix.pc-clone.32bit:821 comp.unix.sysv386:26518 comp.unix.bsd:9363 comp.os.linux:20500 Newsgroups: comp.unix.pc-clone.32bit,comp.unix.sysv386,comp.unix.bsd,comp.os.linux Path: sserve!manuel.anu.edu.au!munnari.oz.au!spool.mu.edu!yale.edu!ira.uka.de!math.fu-berlin.de!informatik.tu-muenchen.de!roell From: roell@informatik.tu-muenchen.de (Thomas Roell) Subject: Re: ET4000/W32 and VESA VL-Bus In-Reply-To: gab10@griffincd.amdahl.com's message of 23 Dec 92 05:03:36 GMT References: <BzBEI1.CH@aeon.in-berlin.de> <1992Dec20.153314.24148@Informatik.TU-Muenchen.DE> <BzKqwn.5vA@wimsey.bc.ca> <003g02AH30U501@JUTS.ccc.amdahl.com> Sender: news@Informatik.TU-Muenchen.DE (USENET Newssystem) Organization: Inst. fuer Informatik, Technische Univ. Muenchen, Germany Date: Sat, 26 Dec 1992 09:21:01 GMT Message-ID: <1992Dec26.092101.4257@Informatik.TU-Muenchen.DE> Lines: 31 >Don't overlook bus width in your analysis. The W32 sounds like it is 32 bit >wide path instead of the 8 (16?) - bit wide path of the standard ET4000. >This would quadruple (double?) the bandwidth of any type of ram access. Hmmm.... this would be an argument, depending on what you mean. Normally you have TWO busses on a graphics chip, the bus to the video memory and the bus to the host system (and if you have VRAMs, the bus to the RAMDAC is a third one). The DRAM (video memory) bus is traditionally 32 bit wide, since 1MB DRAM is build from 8 256x4 DRAM chips. The host bus (read ISA/EISA/MCA) is normally 16bit wide. That means your argument dosn't apply here directly. BUT thet ET4000/W32 has a 32bit wide host bus interfeace which means the path 486 -> ET4000/W32 will be faster throu the increased bus width, but that doesn't affect the internal access time to video memory. In fact if you assume that the VL bus has a write throuput of 33MB/sec (yes, this was actually measured, not a theoretical limit), then the DRAM access sped of the ET4000/W32 will limit your performance again. - Thomas -- ------------------------------------------------------------------------------- Das Reh springt hoch, e-mail: roell@sgcs.com das Reh springt weit, #include <sys/pizza.h> was soll es tun, es hat ja Zeit ...