Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ulowell!cbmvax!jesup
From: jesup@cbmvax.UUCP (Randell Jesup)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Disk drive & blitter hardware
Message-ID: <6788@cbmvax.UUCP>
Date: 8 May 89 02:55:53 GMT
References: <1989May2.114259.21058@ziebmef.uucp>
Reply-To: jesup@cbmvax.UUCP (Randell Jesup)
Organization: Commodore Technology, West Chester, PA
Lines: 28

In article <1989May2.114259.21058@ziebmef.uucp> mcp@ziebmef.UUCP (Colin Plumb) writes:
>a track, giving 66,666 data bits.  I'm wondering if I could fit 65536
>data bits + header information (for 8K of *formatted* capacity per
>track, 10x128K = 1,310,720 bytes per floppy) in there, but I don't
>know the acceptable speed variations in a floppy drive.  Does anyone else
>know how fast a drive can spin and still be considered acceptable?

	Specs are: nominal rotation time: 200ms.
		   allowable variance in rotation speed: +- 1.5%
		   allowable variance in system clock:   +- 5%
		   nominal clock speed                   + 2.5%

	So, maximum bits are nominal*1.015*1.05*1.025, minimum are
nominal*.985*.95*1.025.  Nominal bits are something like 6250*8*2 bits.

>Finally, the disk hardware.  Is it capable of maintaining sync over a
>14us period between 1's?  Can it handle the increase in DC bias?  And

	I don't know.

>is there a reason the trackdisk.device currently avoids the DSKSYNC
>register?  It looks like it would save quite a bit of data shuffling.

	Yes, it would: the trackdisk was coded before the feature was
available.  This is being corrected.

-- 
Randell Jesup, Commodore Engineering {uunet|rutgers|allegra}!cbmvax!jesup