Re: Help needed

From: Marko Mäkelä (
Date: 2001-09-03 11:57:21

Hello Ruud,

> Unfortunately most disks I have laying around are < 500 MB :( So I cannot
> use LBA anyway (for the moment).

I don't think that it is a good idea to use obsolete hardware in projects
that are intended to be replicated.  Remember the PC-keyboard interface
that uses a no-longer-available programmable Dallas switch matrix and a
PC/XT keyboard?  Or the MFM hard disk interface for the C64 that used an
ISA-based MFM controller card?  Those parts were difficult to get already
5 years after the projects were published.

While you may have cheap obsolete hardware lying around, others don't, and
it may be difficult to get it in a few years.  The cure is a modular
design where the low-level access methods are encapsulated behind
higher-level interfaces.

> That is correct. But now I need someone willing to translate this equation
> in ML. The only way _I_ know how to do multiplications is by doing a loop of
> addititions.

A more efficient way is similar to the square-and-multiply algorithm,
except that here it is called the shift-and-add algorithm.  The loop goes
something like this: start with result=1, and loop until multiplier is
zero.  On each iteration, divide the multiplier by 2 (shift right) and
double the result (shift left).  If the multiplier was odd (C flag set),
add the multiplicand (which remains constant during the loop) to the

I'm sure that an implementation of this algorithm is available in a place
the The Fridge.


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