Here is a good post from the other thread:
Extracts from the Drug Trends Bulletin, June 2002, just received, should clarify some of these questions...
KEY POINTS
1. Amphetamine and methamphetamine (also known as "methylamphetamine") are closely related chemically and have similar kinds of effects on the user, but methamphetamine is the more potent form with stronger subjective effects.
2. Throughout the 1980s, the form of illicit amphetamine most available in Australia was amphetamine sulfate. In the financial year 2000/2001, however, 91% of the seizures of this family of drugs were of methamphetamine.
3. Although there is disagreement between both users and key informants about the forms of methamphetamine currently available, it appears that there are at least four main classes. This Bulletin refers to them as:
(i) "Speed" - also known as goey or whiz, this is methamphetamine powder that is manufactured in Australia and ranges in colour from white to yellow, orange, brown or pink. It is usually of relatively low purity, although the purity of speed may be increasing.
(ii)"Pills" - methamphetamine tablets that are mostly manufactured in Australia and are generally sold as "ecstasy". Sometimes these "fake ecstasy" tablets are mixed with drugs like ketamine to try to mimic the effects of MDMA (real ecstasy). MDMA is almost always imported, as few illicit chemists in Australia have the expertise to make it here.
(iii) "Base" - also called paste, wax, point and pure, this is an oily, gluggy or pastey type of damp, sticky powder that often has a brownish tinge and is difficult to dissolve for injection without heat. Base is manufactured in Australia and is usually of relatively high purity.
(iv) "Ice" - also called shabu, crystal, and crystal meth, this is high purity methamphetamine crystals or coarse powder that ranges in colour from translucent to white, but may have a green, blue of pink tinge. True "ice" is manufactured in Asia and imported into Australia.
Source: IDRS (Illicit Drug Reporting System) prepared by Libby Topp, National Drug and Alcohol Research Centre, and Adam Churchill, Australian Customs Service.
This Drug Trends Bulletin goes into detail on all of these points, but this is the summary.
It seems to confirm my impression that "ice" in Australia is a synonym for methamphetamine - as fairnymph has pointed out, in the USA at least, "ice" is 4-MAR.
So it seems the overwhelming majority of 'speed' on the streets you will encounter is methamphetamine.