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From: guest@nemesis.UUCP Date: 11 Jul 93 16:29 CDT Newsgroups: comp.os.386bsd.questions Subject: Re: mitsumi CD-ROM drive Message-ID: <-21066809@nemesis> Path: sserve!newshost.anu.edu.au!munnari.oz.au!network.ucsd.edu!usc!bloom-beacon.mit.edu!news.kei.com!news.oc.com!utacfd.uta.edu!trsvax!trsvax!nemesis!guest Nf-ID: #R:<20bkii$5pe@betty.GPav.GEC.COM>:-31:nemesis:-21066809:000:4131 Nf-From: nemesis.UUCP!guest Jul 11 16:29:00 1993 References: <20bkii$5pe@betty.GPav.GEC.COM> Lines: 78 <> [0]> Is there a drivre for the Mitsumi CD-ROM drive and if so where can I [0]> get one, or can someone mail me one?? [1]The driver is being worked on. Holger Veit is working on the data part, [1]and I'm working on the audio part. My code should be done shortly [1](probably over the weekend). I don't know how long Holger will take, [1]but I don't expect it to be very long as he was working on DMA transfers [1]last I heard. [1] [1]After that, we'll probably want to test it for a bit. I don't know if [1]Holger has anyone lined up for alpha/beta testing, but I'll see about [1]adding your name to the list. Beware. Speaking as someone who had access to actual Mitsumi source code and drive specifications, I cannot advise anyone to seriously consider any of Mitsumi's current or earlier CD-ROM drive offerings. By this I mean the clamshell version (push-click-pull tray, raise lid, either 850 or 390 msec versions), or the motorized tray version (seen with BSR plate from DAK or in Tandy VIS system, 1,300 msec (yes, 1,300 msec!)). All of these drives are frequently seen with various brand-name labels on them, including Acer, BSR and Tandy, and can be found for $175 to $299, depending on the shop. The Mitsumi MTBF (mean time between failure) on these drives is listed at under 9000 hours, well below what you would find on any other drive out there. There are several reasons for this low MTBF: (1) Brush-style DC motor on optic transport (some models also have one on the spindle too, which must be equipped with a spin-down-when-idle function to avoid burning out too quickly) and, (2) rubber band drive belt for optical pick-up transport on some models, a nylon wormgear on others. The clamshell model can also damage discs if the door is opened too quickly and the disc is still spinning. This should be impossible with the motorized tray, but every now and then it will open the tray with the disc still spinning and scraping around the tray. There are also numerous firmware revisions, none of them fix all the bugs. Command and functions appear in one and disappear (or quit working in the next.) Finding a single driver that works on every iteration is probably impossible. Mitsumi has not managed that yet for DOS. The DOS driver(s) they provide is a massive joke, obviously written by someone who had never written 80x86 assembly before. Did you know you must always CLC before doing an ADD? And AX is the only register that conditional operations can be done in? Whoever wrote that code thought so. The drive provides R-W subcodes (nice feature), but a massive amount of code is required to de-interleave, error correct, and get around bugs in the firmware. The drive interface is also pretty efficient, according to the Microsoft benchmark. The motoroized drive had 8% CPU overhead on a 12MHz 286 system, while a popular drive from another vendor had 30% CPU overhead on a 25MHz 486SX computer. The difference is mainly DMA vs non-DMA, with many drives being non-DMA. Both Mitsumi models can fo 150K/sec streaming data transfers, but the motorized version is highly sensitive to ground loops between data, power cables and the frame. The presence of a ground loop can drop the data rate to as low as 23K/sec. There is also a bug in the Mitsumi firmware (ALL VERSIONS to my knowledge) that if you have a mixed-mode disc (track 1 data, track 2-n audio) and you attempt to read a file or block within about 40K of the end of Track 1, it will get read errors and start playing music out the D-to-A. We had to master all our disc with a large file (or oversized partition ) that was never accessed in the last part of track 1 to avoid this problem. If its just a HS/ISO disc, the dead space is still required or else the drive will get read errors trying to read-ahead into the lead-out area. Finally, at last report, Mitsumi still doesn't have a drive that would do multi-session photo CD correctly. Tandy gave up and stopped using Mitsumi drives last in Spring 1992 for computers and switched to a LMS (Philips in America) drive. Bottom line, you pay for what you get. :-(