WITH 16x fewer registers, that equates to about 1 chip's worth of registers (remember a stick of DRAM often has 8-16 individual chips on it). While this is already clearly a huge problem, consider additionally that DRAM is made with trench capacitors, unlike SRAM. DRAM is dramatically slower and more dense than SRAM. So we either sacrifice speed, or bloat our one-chip's-worth of area by a few factors, say x4-8.
Then there's practicalities like sense amp design. Large register arrays are not read in a digital fashion, and current L2 and L3 sizes already press their sense amps to their limits. DRAM also uses sense amps, but the amps are again slower and larger.
Then there's practicalities like sense amp design. Large register arrays are not read in a digital fashion, and current L2 and L3 sizes already press their sense amps to their limits. DRAM also uses sense amps, but the amps are again slower and larger.
http://en.wikipedia.org/wiki/Sense_amplifier