Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!olivea!uunet!snorkelwacker.mit.edu!bloom-beacon!eru!hagbard!sunic!liuida!isy!ingemar From: ingemar@isy.liu.se (Ingemar Ragnemalm) Newsgroups: comp.sys.mac.hardware Subject: Re: LC questions Message-ID: Date: 14 Feb 91 09:37:15 GMT References: <631@ssdc?> <1991Feb11.015535.29892@agate.berkeley.edu> Sender: news@isy.liu.se (Lord of the News) Organization: Dept of EE, University of Linkoping Lines: 46 labc-1ic@e260-1e.berkeley.edu (Willy S. Liao) writes: >In article <631@ssdc?> jbasara@ssdc (jim basara) writes: >> >>...stuff deleted... >> >>2. I see on the Mac product list that I have that there is something called >>a Macintosh LC 512K VRAM SIMM which supposedly allows greater color depth. >>What is this item and why is it needed for the LC? What is different about >>the LC architecture to require this SIMM? Is there a significant difference >>between the graphics capabilties between the LC and the si? >Yes, there is a difference between the LC & si. The si internal video is >virtually the same as the ci's--it uses main DRAM, NOT dedicated VRAM. Due >to technical details about bus contention, this can impose a slight >performance penalty on CPU accesses to RAM on the si & ci, depending >on how deep the screen is. The fact is that in *some* cases, the performance penalty is severe. My IIsi runs slower *only* with 8-bit mode *and* Multifinder. It all depends on in what memory the active program runs, I guess. There is no noticable dependency on screen depth, except for the amount of data involved. Just displaying 8 bits instead of 4, 2 or 1 makes no difference. >The LC has dedicated VRAM on the motherboard, separate from the 2 megs >DRAM soldered on for main memory. --more-- >On this subject, you should be aware that since the data path is only 16 bits >wide, video writes will be slower than on the IIsi, even accounting for the >dedicated VRAM on the LC. I don't think it's that much slower, but check >with someone who owns an LC on this subject. If you do a lot of graphics, >this may be a problem. It is not noticable as far as I could tell. All tests I could run said that the LC is as fast as a (plain) Mac II. The IIsi is usually noticably faster, but when it slows down, it is slower than both a MacII and an LC. --more stuff deleted-- -- Ingemar Ragnemalm Dept. of Electrical Engineering ...!uunet!mcvax!enea!rainier!ingemar .. University of Linkoping, Sweden ingemar@isy.liu.se