deep pipes need high Mhz, even on a G4.
Now, the unfortunate part:
- more pipeline stages (nearly double; that would yield results similar to P3 to P4)
- How much wil this cost?
I totally agree.
I did a little research...
I took an average of the results gained in the Photoshop, iTunes, Cinebench and filemaker test in
this barefeats test of a 533Mhz G4 vs 733Mhz G4 with L3 and some more recent models. Although the 733Mhz G4 has a 37.5% higher clock speed, the average speed gain was only 20.5% over the 533Mhz G4, effectively making it a little over 640Mhz in reality.
With this in mind, I worked out the effective speeds of a few possible clock speeds we might see with the performance penality of the previous 3 stage increase used to downgrade the Mhz to what the current 7455 G4s would need to be to match it's performance :
(effective clock speed in brackets)
1.133 Ghz (993 Mhz)
1.267 Ghz (1.11 Ghz)
1.533 Ghz (1.34 Ghz)
Obviously this is all theoretical. DDR, larger caches, smaller die size etc... will add serious muscle to whatever negative effect a pipeline stage increase has anyway.
The wierd thing is, if you look at results from any G4 vs Athlon crunch test, the G4 has always matched the Athlon MHz for Mhz no matter what version of the Athlon or G4 is being tested. That means that seeing as the current single CPU results from a 1Ghz G4 with SDRAM vs a 1.4Ghz althon with DDR show that a 1.4Ghz G4 with the current motherboard would match the Athlon, Imagine what damage a 1.5Ghz G4 on a DDR motherboard is going to do to a Pentium 4!
