Re: WTB:Apple Hi-Speed SCSI

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

stephen e buggie <buggie@ben11.unm.edu> wrote:

> You do NOT need the "high speed version."  It is no faster than other
> versions.

I beg to differ.  I have owned both cards, and done speed tests on them,
as well as observed their apparent speed.

With DMA enabled, the high-speed card is considerably faster than the
original one.  Under ProDOS-8, the difference is noticeable but nothing
to get excited about.  Under GS/OS, the difference is very significant
(at least twice as fast for typical operations).

The RamFast is faster still (particularly in ProDOS-8).

I don't have the actual numbers handy, but from memory, the original
Apple card can't transfer more than about 80KB per second, under ideal
conditions (block transfers under GS/OS).  The high-speed card is more
like 200KB to 300KB per second for similar transfers, and can peak at
1MB per second (on a IIgs) with specially written software.

If DMA is disabled, the high-speed card loses most of its advantage.

One other reason to prefer a High-speed SCSI card over an original Apple
one is that it supports more volumes/partitions under ProDOS-8.  The
original card is limited to 7 volumes, which means that you can't access
more than 7 * 32 = 224 MB of storage.  The high-speed card is only
limited by ProDOS's unit numbering scheme (14, minus two per slot
containing a disk controller, minus one for /RAM.)

-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P O Box 27-103, Wellington, New Zealand