rogers@orion.SRC.Honeywell.COM (Brynn Rogers) (02/14/89)
Has anybody had any experience with perstore controllers and Maxtor drives??
I have a Maxtor xt-1140 120 Meg drive (MFM) and from what I hear I could
get as much as 200 Meg out of it.
What is the interleave of a perstore controller (1:1, I guess)?
All Maxtor drives use plated media; I understand plated media is a requirement
for RLL drives. (please tell me if I am mistaken)
P.S. I replied directly to someone that also has a Maxtor drive. due to
unforseen circumstances, all my mail went elsewhere and was deleted.
All I know is that something about maxtor went into the great bit bucket
in the sky. Thats why I haven't replied to _______ out there.
'Seek out new life and civilizations' | Brynn Rogers Honeywell S&RC
"Honey, come see what I | UUCP: rogers@orion.uucp
found in the refrigerator!" | !: {umn-cs,ems,bthpyb}!srcsip!rogers
| Internet: rogers@src.honeywell.comsilver@eniac.seas.upenn.edu (Andy Silverman) (02/15/89)
In article <16761@srcsip.UUCP> rogers@orion.UUCP (Brynn Rogers) writes: >Has anybody had any experience with perstore controllers and Maxtor drives?? >I have a Maxtor xt-1140 120 Meg drive (MFM) and from what I hear I could >get as much as 200 Meg out of it. > >What is the interleave of a perstore controller (1:1, I guess)? > >All Maxtor drives use plated media; I understand plated media is a requirement >for RLL drives. (please tell me if I am mistaken) Well, controllers don't have interleave factors, drives do. You set the interleave factor during the low-level format of the drive, depending on things like the clock speed of your computer. If the interleave is too low (say 1:1 on an XT) the drive will try to send info faster than the computer can handle it and drive access slows incredibly as a result. The trick is trying to optimize interleave to get the highest throughput rate. Also, I don't think plated media is required for an RLL drive, it's just that plated media are more durable and immune to head crashes than standard oxide coatings. RLL drives do require slightly more stringent timing and such in the analog control card in the drive, however. Andy Silverman Internet: silver@eniac.seas.upenn.edu CompuServe: 72261,531
malloy@nprdc.arpa (Sean Malloy) (02/15/89)
In article <16761@srcsip.UUCP> rogers@orion.UUCP (Brynn Rogers) writes: >What is the interleave of a perstore controller (1:1, I guess)? The manual I got with my controller recommends the following interleave values: 4 for a PS180 with XT ROM on any machine (the manual refers to 4.77 MHz XTs and 6 MHz ATs) 8 for a PS180 with AT ROM on AT machine (the manual refers to 6 MHz ATs) (The ROM is one of the socketed chips on the controller. There will be a label on it indicating ROM type and version number. Mine says XT9-1.03) The Perstor controllers put more sectors on a track than either MFM or RLL controllers do: 31 for the PS180, 34 for the PS200. The additional sectors radically change the best interleave from what the 'intuitive' value is based on the drive specs. The Perstor controller's data transfer rate is _very_ dependent on the correct interleave. I discovered this the hard way. I have a 10 MHz XT clone, so I figured I would be able to decrease the interleave, and set it to 3:1 when I installed a 40Mb drive. A couple of days later, I downloaded a file with some information about using Perstor controllers from SIMTEL20, and found the following suggestion: Get a copy of CORETEST (available on SIMTEL20), then format the disk with various interleaves -- the format only needs to run for about 90 seconds for CORETEST to find enough formatted space to work with -- and compare the data transfer rates for various interleave values, picking the interleave just before the one that _reduces_ the rate when you increase the interleave. When I ran CORETEST on my 3:1 interleaved disk, it gave me a rate of 29.56 Kb/sec. Reformatting the disk to the recommended 4:1 gave me a rate of 241.78 Kb/sec (at 5:1, it dropped to 181.36, so 4:1 was the best). Sean Malloy Navy Personnel Research & Development Center San Diego, CA 92152-6800 malloy@nprdc.arpa
samc@hpccc.HP.COM (Samuel Chau) (02/16/89)
> Has anybody had any experience with perstore controllers and Maxtor drives?? > I have a Maxtor xt-1140 120 Meg drive (MFM) and from what I hear I could > get as much as 200 Meg out of it. I haven't actually tried formatting an XT-1140 with the Perstor PS180, but I'm quite certain that if the drive was manufactured recently (less than 2 years old or so) then you should have no trouble getting 200 Megs out of it. > What is the interleave of a perstore controller (1:1, I guess)? The best that the PS180 can do is 3:1 interleave, which translates to a maximum transfer rate of about 310 Kbytes/sec. Having a fast CPU or fast AT bus clock won't be of much help, since the overhead is in the controller itself. In fact, the optimum interleave should be the same for a 6 MHz AT as for a 20/25 MHz 386 PC. I believe Perstor is working on an improved version of the controller that can support a 1:1 interleave. (Don't know the targeted release date, sorry) > All Maxtor drives use plated media; I understand plated media is a requirement > for RLL drives. (please tell me if I am mistaken) The first statement is correct. Maxtor doesn't use oxides. But I don't think plated media is a must for RLL drives. It will certainly help, since plated media is of higher resolution than oxide media. What is required of RLL drives is high rotational accuracy and sufficient media resolution. Flux density on the surface is NOT higher for RLL compared to MFM encoding, but the timing requirements (i.e. accurate placement of the flux reversals on the surface) are much more critical for RLL. Perstor controllers have similar requirements as RLL. Rotational accuracy of the drive spindle motor must be kept within 1%. Plated media drives generally have a better chance of working with the PS180 than oxide drives. Cables must be of good quality, kept as short as possible, and of course, properly terminated. Given all this, the chance of a Maxtor XT-1140 working as a 200 Meg drive should be excellent. Perstor also has a list of drives that are supported by the PS180. Virtually all Maxtor ST-506 models utilizing MFM encoding are on the list. In case you don't know, there are two Perstor controllers currently in the market. The PS180-16F is a floppy/HD combination controller with a 16-bit bus interface. The PS180 is a HD-only controller with an 8-bit interface. I was told that the PS200 series controllers would soon be released from Perstor. These controllers will format the drives to 34 sectors/track, thus giving you 2X the capacity of MFM-encoding. RLL-certified drives are required, though. > 'Seek out new life and civilizations' | Brynn Rogers Honeywell S&RC > "Honey, come see what I | UUCP: rogers@orion.uucp > found in the refrigerator!" | !: {umn-cs,ems,bthpyb}!srcsip!rogers > | Internet: rogers@src.honeywell.com Sam Chau HP Cupertino samc@hpda (408) 447-0238 '...To boldly go where no Winchester has gone before..."
davidsen@steinmetz.ge.com (William E. Davidsen Jr) (02/16/89)
In article <7981@netnews.upenn.edu> silver@eniac.seas.upenn.edu.UUCP (Andy Silverman) writes: | things like the clock speed of your computer. If the interleave is too low | (say 1:1 on an XT) the drive will try to send info faster than the computer | can handle it and drive access slows incredibly as a result. The trick is | trying to optimize interleave to get the highest throughput rate. Let me see if I can say that a little more clearly. When the CPU requests reading of a sector, it is transfered off the disk, through the controller and either into the CPU or memory, depending on whether a DMA controller is being used (most AT's don't use DMA for hard disk). The transfer rate for a sector is completely unrelated to the interleave factor. After reading one sector, the CPU will do some processing and then read another. This is where interleave comes in. If the interleave is, say, 3:1, there are two sectors between consecutively numbered sectors. While these pass under the heads the CPU can process the first read. By the time the CPU is ready to read another sector the next sector is almost at the heads, and the read takes place very quickly. If the interleave is is little large, one or more unwanted sectors must pass by the heads before the desired sector comes along. This will slow access by a bit. If the interleave is too small, the desired sector will have passed the head already, and the disk must rotate one whole revolution (or a little less) before the read can take place. This can reduce transfer rate down to the floppy disk range. There is no "best" interleave, there are only compromises. If a small interleave is selected (as low as 2:1 on an AT) programs will load very quickly. Since there is very little CPU used in loading an image, the CPU can "keep up with" the 2:1 interleave. That same interleave may slow an application by a factor of four or five, because the data requires more processing. Needless to say, the only solution which isn't a compromise is a 1:1 track buffered controller. -- bill davidsen (wedu@ge-crd.arpa) {uunet | philabs}!steinmetz!crdos1!davidsen "Stupidity, like virtue, is its own reward" -me