ataMan claims to have written the firmtek firmware

[chrisNova777]

https://www.macgurus.com/forums/showthread.php?19794-Sonnet-Tempo-133-slower-than-G4-onboard-ATA&s=ddb3daee038843991f580a9cf9f1aa2b&p=79969#post79969

https://www.macgurus.com/forums/search.php?searchid=347864

Sonnet tech. support is usually good, they could do a better job this time!
I wrote the firmware for TurboMax/33, UltraTek/66, Tempo/100, Tempo/133 and the entire SeriTek controller family (+ some undisclosed OEM cards, too). Also the ATA code inside of the old FWB HDT 2.0 (NOT the current one!!!) is mine, so I likely can give you a competent answer.

1) There is NO incompatibility between Sonnet Temo/133 and the G4/AGP. Simply: Sonnet Tempo/133 uses the Promise PDC 20269 chipset. That chipset is great on certain architecture G4 but the first generation of G4 slows it down to a good degree. Apple uses a similar chipset after they got the clue from us in their first XServe and it works great there. But there is no panacea: the same chipset good in XServe is mediocre on writes in G4/AGP. G4/AGP is not easy to deal with: you will see similar results from Acard chips, too - but they do a bit better on the write (40-something). The first generation G4/AGP is VERY slow on the PCI bus and so far, only following products perform well: the SeriTek/1S2, the SeriTek/1SE2, the SeriTek/1V4 and the upcoming SeriTek/1VE4. These SATA controllers have special performance tuning for the G4/AGP.

2) The Sonnet Tempo SATA and SeriTek/1S2 are not the same. The color of the PCB is red on SeriTek and violet on Tempo SATA. You likely will see identical feature set and identical performance. Ask "gurus" and rest of the forum visitors regarding SeriTek/1S2 and Sonnet Tempo similarities - I maynot provide more information.

3) On your machine expect to get about 140-150 MB/Sec on both read and write using four SATA drives striped on the SeriTek/1V4. No other controller comes even close. That SATA card (PCI-X, runs as 64-bit PCI in G4/AGP) costs $120 versus a 32-bit Acard for ?!?