Owners of Apple's 12in PowerBook G4 will at last be able to bust the 640MB memory limit on their machines without breaking the bank.

US Mac specialist Trans International today launched a 1GB PC2100 SO-DIMM compatible with the notebook. With the 128MB soldered on to the PowerBook's motherboard, users can now equip themselves with just over 1.1GB of RAM.

To date, Apple and major memory vendors have offered only 512MB SO-DIMMs, hence the limit of 640MB.

That's not to say that 1GB SO-DIMMs haven't been available. IBM has offered corporates such a part for its ThinkPad notebooks for some time. The trouble is, prices have rarely descended below the $999 mark - almost as much as you pay for your PowerBook.

Trans' 1GB SO-DIMM isn't entirely cheap. But at $499, it's a darn sight more affordable than before. That said, a 512MB SO-DIMM costs around $100 - half the capacity for around a fifth of the price - which shows how far further the 1GB part's price can fall.

Comparable devices from other suppliers were today listed around the $700 mark. The best UK price we saw was £799. ®