5 Oct
2009
5 Oct
'09
2:43 p.m.
On 5 Oct 2009 at 17:10, Dave McGuire wrote:
New kludges were devised to exceed this ~137GB
plateau
(obviously), but I don't know how they work offhand because I've
never designed with them.
Think "shadow registers"--instead of each 8-bit register in the task
file representing an 8-bit quantity, each will accept two consecutive
output or input commands and accept or return 16 bits. In other
words, each register has a flip-flop that directs I/O to either 8 bit
register. It's not pretty, but it works.
Anyway, early BIOSs don't know how to deal with
this, which is one
of the things that makes this XTIDE controller special.
Well, one can also declare a minimal conventional CHS partition from
which one boots and then install a driver to access the remainder of
the drive. Something akin to the way a drive extender works. When I
had my AT, I used some 1224 cylinder MFM drives that early BIOSes
didn't know how to handle. So I booted from a smaller partition and
then loaded my own driver. With an RLL controller, that gave me a
whopping 250MB or so.
--Chuck