sonny@charybdis.harris-atd.com (Bob Davis) (09/10/90)
Have you ever RLL formatted an ST251 42Mb MFM drive? Can you get it to go 63Mb that way? I have an Adaptec 2372 RLL controller. If RLL is possible, then by the DEBUG g=c800:5 jazz, do I declare 820 cylinders and 6 heads? What are the details of what I must do to try RLL formatting? Does the 50% increase in drive capacity under RLL formatting compared to MFM *always* come because there are 26 sectors/track for RLL, and only 17 sectors/track for MFM? And therefore does one always use the SAME number of cylinders and heads for RLL as for MFM? Thanks. ______________________________________________________________________________ Bob Davis \\ INTERNET : sonny@trantor.harris-atd.com | _ _ | Harris Corporation, ESS \\ UUCP : ...!uunet!x102a!trantor!sonny |_| |_| | | Advanced Technology Dept.\\ AETHER : K4VNO |==============|_/\/\/\|_| PO Box 37, MS 3A/1912 \\ VOICE : (407) 727-5886 | I SPEAK ONLY | |_| |_| | Melbourne, FL 32902 \\ FAX : (407) 729-2537 | FOR MYSELF. |_________|
brim@cbmvax.commodore.com (Mike Brim - Product Assurance) (09/10/90)
In article <4285@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes: > > Have you ever RLL formatted an ST251 42Mb MFM drive? Can you > get it to go 63Mb that way? I have an Adaptec 2372 RLL controller. If RLL > is possible, then by the DEBUG g=c800:5 jazz, do I declare 820 cylinders > and 6 heads? What are the details of what I must do to try RLL formatting? I've been running a ST251 on an Adaptec 2372 for about 2 years with no problem. You only have to declare the 820 cylinders and 6 heads. The only problem you may have are defects. You cannot enter the ones on the defect list and expect them to be marked correctly. Since the Adaptec does a nice low level with verify this MAY not be a problem. I would also run Spin Rite II on it. Before using the drive, test it out. Run any type of hard drive banging program you can find. At least make a batch file to copy files and compare them. Run it for a few days non-stop. > > Does the 50% increase in drive capacity under RLL formatting > compared to MFM *always* come because there are 26 sectors/track for RLL, > and only 17 sectors/track for MFM? And therefore does one always use > the SAME number of cylinders and heads for RLL as for MFM? > If I understand your question correctly, The only (high level at least) diff. between RLL and MFM is the 26 vs. 17 sectors. -- ******************************************************************************** Disclaimer: My company knows not what I say (or do). Mike Brim | Commodore Electronics Limited PC Analyst - System Evaluation Group | West Chester, PA 19380 Product Assurance | InterNet: brim@cbmvax.commodore.com ********************************************************************************
phil@brahms.amd.com (Phil Ngai) (09/10/90)
In article <4285@trantor.harris-atd.com> sonny@trantor.harris-atd.com (Bob Davis) writes: | | Have you ever RLL formatted an ST251 42Mb MFM drive? Can you Yes, with a WD1006V-SR2. For about a year now with no problems. ST4096 too. (I have 180 megabytes). | Does the 50% increase in drive capacity under RLL formatting |compared to MFM *always* come because there are 26 sectors/track for RLL, |and only 17 sectors/track for MFM? And therefore does one always use |the SAME number of cylinders and heads for RLL as for MFM? Yes. RLL simply increases the data bit density (but NOT the flux transition density) and does not affect the geometry (#tracks and #heads) at all. -- Phil Ngai, phil@amd.com {uunet,decwrl,ucbvax}!amdcad!phil
scjones@thor.UUCP (Larry Jones) (09/11/90)
In article <1990Sep10.162707.18613@amd.com>, phil@brahms.amd.com (Phil Ngai) writes: > RLL simply increases the data bit density (but NOT the flux > transition density) and does not affect the geometry (#tracks and > #heads) at all. RLL doesn't affect the geometry but it most certainly DOES increase the flux density. The average density may not increase (I'm not sure), but the maximum density is about 50% greater than MFM. ---- Larry Jones UUCP: uunet!sdrc!thor!scjones SDRC scjones@thor.UUCP 2000 Eastman Dr. BIX: ltl Milford, OH 45150-2789 AT&T: (513) 576-2070 You should see me when I lose in real life! -- Calvin
peng@chaource.cs.wisc.edu (PENG) (09/14/90)
In article <1990Sep10.162707.18613@amd.com> phil@brahms.amd.com (Phil Ngai) writes: |In article <4285@trantor.harris-atd.com> |sonny@trantor.harris-atd.com (Bob Davis) writes: || || Have you ever RLL formatted an ST251 42Mb MFM drive? Can you | |Yes, with a WD1006V-SR2. For about a year now with no problems. |ST4096 too. (I have 180 megabytes). | || Does the 50% increase in drive capacity under RLL formatting ||compared to MFM *always* come because there are 26 sectors/track for RLL, ||and only 17 sectors/track for MFM? And therefore does one always use ||the SAME number of cylinders and heads for RLL as for MFM? | |Yes. RLL simply increases the data bit density (but NOT the flux |transition density) and does not affect the geometry (#tracks and |#heads) at all. I know Mitsubishi is advertising a drive (MR535?) that allows you to format as either an RLL or an MFM drive. But I never see Seagate does this. So what's the catch? Do RLL drives have to be better built? And therefore Mitsubishi doesn't mind that their drives are being formatted in MFM? (because they don't produce "low quality" drive?) I know the flux transition density remains about the same when you use your MFM drive as an RLL drive. But how about "error-correctibility?" I don't know how exactly an RLL drive encodes the data, but it sounds to be more vulnerable to errors since the data bit density is higher. Any one cares to enlighten me? -peng
phil@brahms.amd.com (Phil Ngai) (09/16/90)
In article <11257@spool.cs.wisc.edu> peng@chaource.cs.wisc.edu (PENG) writes: |I know Mitsubishi is advertising a drive (MR535?) that allows you to |format as either an RLL or an MFM drive. But I never see Seagate does this. |So what's the catch? Do RLL drives have to be better built? And therefore |Mitsubishi doesn't mind that their drives are being formatted in MFM? (because It's not primarily a matter of how well they are built. The thing about RLL is that, although it uses the same number of flux transitions as MFM, they must be more precisely placed. Things like a poor signal to noise ratio in the head amplifiers or imperfect write compensation can cause a problem. Apparently Seagate does not want to certify some of their drives as RLL (although many of them do work that way). I think all RLL drives can be used in MFM but there are plenty of rumors about how you can't do this, so I believe the Mitsubishi drive is really a RLL drive and Mitsubishi is simply trying to reassure those people who do not have RLL controllers that they can also use that disk. In my limited experience, most reliable MFM drives work in the RLL mode. I would expect that a drive which failed RLL to be pretty marginal with MFM but I will not claim to be an expert at this, I do feel I have an understanding of how MFM and RLL work at the bit level. No doubt someone will post about how he tried his MFM drive with RLL and it caught fire and burned down his house, but I don't believe it was because of the use of RLL. And there are stories about how if you use an RLL drive with an MFM controller it will give off X-rays and prevent you from having any children, but you shouldn't believe them either. -- Phil Ngai, phil@amd.com {uunet,decwrl,ucbvax}!amdcad!phil "Why would Xerox Corp. want a paperless office?"