P4's but no 512 caches? - why?

[Axel]

I haven't been able to find any listings for a P4 processor with more than a 256 cache on it - I was hoping to find a 512 out there somewhere, but haven't seen one -

Does anyone know why? I haven't yet been able to puzzle that out?

[Axel]

I browsed the intel site and didn't see anything in a p4 listed with more than 256 - so i sent them a note asking why - when, or if I get something back - I'll post here -

[Hellmund]

Unless u get a Xeon PIV socket 478 u won't get 512kb's of cache, that's part of the advantage of moving to 0.13m with northwood, more cache without too much extra cost. Northwood will be released with 512kb.

[Axel]

I actually got information back on this from Intel -

When cutting down the die size of the new 423 and 478 processors away from the slot technology, there simply wasn't room. Also - the change of going from the 25 micron spacing to the 18 micron spacing makes a larger cache much more difficult to engineer into the chip.

Also, and I didn't know this - the 512 caches typically didn't have the transfer rates of the smaller 256 caches on-die - so while you had more room, it was slower - and the vast majority of applications didn't benefit from the extra cache space on-die -

and that's why - according to intel.....

I suspect that the additional speed on the RAM and FSB might change that need - That, or we will see more multi-processor boards out there.

What I'd love to see is more programmers designing for multi-processor kernals - in most systems, only the operating systems makes use of the second processor as far as I know -