Many Scotch whisky drinkers refer to a unit for drinking as a dram. A teaspoonful has been considered equal to one fluid dram for medical prescriptions. Competing with DDR2 was Rambus XDR DRAM. The dram in avoirdupois weighs just under half of the dram in apothecaries'. Modules with multiple DRAM chips can provide correspondingly higher bandwidth. This can be a problem for DRAM and SRAM based memories. Note that the actual memory chips are manufactured by a small number of DRAM manufacturers. The price and speed of Optane memory is between that of DRAM and NAND. Another is selective refresh, which limits self-refresh to a portion of the DRAM array. This is the time to read a random bit from a precharged DRAM array. The republic uses the Armenian dram. It contained an Intel Pentium II (Klamath) CPU, EDO DRAM, and an i440FX chipset. Bus multiplexing requires fewer wires, which reduces costs in many early microprocessors and DRAM chips. "Direct RAMBUS DRAM" ("DRDRAM") was developed by Rambus. This led to his development of a single-transistor DRAM memory cell.