kallaus@leadsv.UUCP (Jerry Kallaus) (12/14/88)
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I just added a C= A2090A and a Seagate ST4096 harddisk to my 2000.
Does anyone have any idea why only 8 out of the 9 heads on this
drive may be used?
Prep accepts 9 as the number of surfaces.
However, when I run FORMAT, for each cylinder counted by the
FORMAT display, from the drive there are 9 quick clicks for the
format followed by what sounds like 9 real fast clicks for
the verify, and then the FORMAT display cylinder number increments
by one and the sound pattern repeats.
When FORMAT said it was formating something like cylinder 127,
the system seemed to hang in a loop, retrying to format that
cylinder. The drive actually has 1024 cylinders. Note that
128*8=1024. It seems to me that it's behaving as if there
was one head that spans 9 cylinders instead of 9 heads
spanning one cylinder. It also seems like someone only
allowed 3 bits somewhere for the number of heads.
Any ideas why this is?
--
Jerry Kallaus {pyramid.arpa,ucbvax!sun!suncal}leadsv!kallaus
(408)742-4569
"Funny, how just when you think life can't possibly get
any worse, it suddenly does." - Douglas Adamsjesup@cbmvax.UUCP (Randell Jesup) (12/15/88)
In article <5381@leadsv.UUCP> kallaus@leadsv.UUCP (Jerry Kallaus) writes: >I just added a C= A2090A and a Seagate ST4096 harddisk to my 2000. > >Does anyone have any idea why only 8 out of the 9 heads on this >drive may be used? The current 2090 firmware (in the ROM for the Z80 onboard) only supports the old St506 standard of 8 heads. Many modern drives support using one of the now unused lines (I think the reduced write current line) as an additional head select line. Dale Luck burned a custom version of the ROM for himself that does this, I'd advise contacting him (amiga!gfxbase!dale, I think). -- You've heard of CATS? Well, I'm a member of DOGS: Developers Of Great Software. Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup
lphillips@lpami.van-bc.UUCP (Larry Phillips) (12/16/88)
In <5381@leadsv.UUCP>, kallaus@leadsv.UUCP (Jerry Kallaus) writes: > I just added a C= A2090A and a Seagate ST4096 harddisk to my 2000. > > Does anyone have any idea why only 8 out of the 9 heads on this > drive may be used? ST506 specifies 8 heads. ST412 allows more. The 2090 is an ST506 only controller. -larry -- "Intelligent CPU? I thought you said Intel CPU!" -Anonymous IBM designer- +----------------------------------------------------------------------+ | // Larry Phillips | | \X/ lphillips@lpami.wimsey.bc.ca or uunet!van-bc!lpami!lphillips | | COMPUSERVE: 76703,4322 | +----------------------------------------------------------------------+
blgardne@esunix.UUCP (Blaine Gardner) (12/16/88)
From article <5381@leadsv.UUCP>, by kallaus@leadsv.UUCP (Jerry Kallaus): > I just added a C= A2090A and a Seagate ST4096 harddisk to my 2000. Welcome to the club! > Does anyone have any idea why only 8 out of the 9 heads on this > drive may be used? The original A2090 only supports 8 heads. This was supposed to be expanded to >8 with the A2090A according to "highly placed sources" :-) (Dale Luck and a couple of others). Unfortunatly, this doesn't seem to be the case. I got one of the first A2090A's, and a friend got his A2090A this month. All the part number stickers are the same on all the PALs and PROMS, so it looks like there have been no updates made yet. > Prep accepts 9 as the number of surfaces. > However, when I run FORMAT, for each cylinder counted by the > FORMAT display, from the drive there are 9 quick clicks for the > format followed by what sounds like 9 real fast clicks for > the verify, and then the FORMAT display cylinder number increments > by one and the sound pattern repeats. Yep, that's exactly what happened to me, lots of funny noises when you try formatting with 9 heads. If you drop down to 8 heads, the format is nearly silent, just one "click" per track. > When FORMAT said it was formating something like cylinder 127, > the system seemed to hang in a loop, retrying to format that > cylinder. Ditto, with 9 heads, the format dies about cylinder 126. Sometimes the system crashes, sometimes the format just hangs. If you format with 8 heads, it will format out to cylinder 1023 without any problem. It took mine just under a minute a megabyte (my two 34M partitions formatted in 32 minutes each). > The drive actually has 1024 cylinders. Note that > 128*8=1024. It seems to me that it's behaving as if there > was one head that spans 9 cylinders instead of 9 heads > spanning one cylinder. No, the number of heads doesn't relate to the number of cylinders at all. What you've got is 17 sectors * 512 bytes per sector = 8704 bytes per track. 8704 * 1024 tracks = 8,912,896 bytes. If you multiply that by 9 heads you get 80,216,064 bytes (note that Segate is cheating here, 1K is 1024, not 1000, so this "80 meg" drive is really only 78.3 meg). And if you are forced to use only 8 heads you get 71,303,168 (69.6 meg). > It also seems like someone only > allowed 3 bits somewhere for the number of heads. Bingo! That's the problem exactly. > Any ideas why this is? The original ST506 spec allowed 3 bits for head select, and that limits you to 8 heads. When bigger drives were created, one of the other signal lines was stolen for a 4th head select line. This gives you capacity of using 16 heads, but I'd happily settle for 9. I'd guess that when there's an attempt to access the 9th head, whatever signal line that should be the 4th head select gets hit, and you get some unwanted reaction from the drive, rather than selecting head 8 like you wanted. (Anyone know what signal was stolen to make the 4th head select line?) Dale Luck mentioned that it was simply an EPROM change to fix the A2090A to use more than 8 heads. And I remember someone else saying that the A2090A hardware supports >8 heads, and the limit was in the software. So, if anyone at (or near :-) Commodore can provide a way to use more than 8 heads there will be at least 3 of us eternally in your debt! All I want for Christmas is my missing 8.7 megabytes! -- Blaine Gardner @ Evans & Sutherland 580 Arapeen Drive, SLC, Utah 84108 Here: utah-cs!esunix!blgardne {ucbvax,allegra,decvax}!decwrl!esunix!blgardne There: uunet!iconsys!caeco!pedro!worsel!blaine "Nobody will ever need more than 64K." "Nobody needs multitasking on a PC."