Re: High Speed CD-ROM drives

[dempson@actrix.gen.nz (David Empson)]

"Joel" <joelbuckley54.nospam.@hotmail.com> wrote:

> David Empson wrote:
> > At the very least, you won't get full performance out of a CD-ROM drive
> > faster than 1x, due to the limited throughput of the Apple II SCSI
> > cards.  The original SCSI card can't even sustain the throughput
> > required for 1x, but the high-speed SCSI card might be able to manage 2x
> > (under GS/OS).
> 
> I saw dramatic improvement over the 1X drive.
> In testing, a CD-600 is 4.5X as fast a CD-150.
> 
> These are times for a 65535 block verify under GSOS 6.01
> This is with DMA.
> (Speed) Drive  -  DMA Time  - Calc Speed
> (1X) CD-150  - 362s  - 93kB/s
> (2X) CD-300  - 103s  - 326kB/s
> (4X) CD-600  - 80s  -  420kB/s
> 2GB hard drive 64k block - 120s  - 280kB/s

I'm impressed!  I'd be interested to find out whether a CD-1200 or
CD-2400 can get a little more speed out of the HS SCSI card.  It can
theoretically get transfer rates approaching 1 MB per second on a IIgs
(half that on a IIe), but I don't know whether the GS/OS driver is able
to sustain that sort of throughput.

> I think one of the faqs talked about having to reboot on a change of CDs.
> I have NOT seen that.

This might be confusing a separate issue - with the original Apple SCSI
card under ProDOS-8, you have to reboot if you change a removable
cartridge (e.g. SyQuest or Zip Drive), but this doesn't apply to CDs.

It might be an issue with newer models of drive if the computer is
unaware that the CD has been ejected manually.

The later drives obviously changed the LOCK/UNLOCK/EJECT commands in
some way which breaks these features of the Apple II SCSI card drivers.

-- 
David Empson
dempson@actrix.gen.nz