As another poster has said, around 2000/2001 there were many PC motherboards for which the maximum RAM capacity was 640 MB of SDRAM (though depending on the mot

As another poster has said, around 2000/2001 there were many PC motherboards for which the maximum RAM capacity was 640 MB of SDRAM (though depending on the motherboard the capacity limit could have other values, e.g. 512 MB or 768 MB were other frequent values). Only around 2003, motherboards where you could install up to 4 GB of DDR memory became widespread. I had a few such motherboards, with Pentium III "Coppermine" and with AMD Athlon "Thunderbird" (with 3 DIMM sockets, 2 accepting 256 MB modules and 1 accepting 128 MB modules). While I had initially equipped them with less memory, i.e. either 128 MB or 256 MB, because of the high cost at that time, eventually I had maxed up the installed memory to 640 MB on the Athlon motherboards. At that time, the memory controller was not included in the CPU, but it was contained in an external chip, the Northbridge. The MB chipsets could come from various vendors, including Intel and Via. Depending on the chipset, different maximum amounts of SDRAM could be supported. Sometimes there were also limits for the maximum amount of RAM caused by the L2 cache controller, due to the size of the tags required in cache lines. Even with the same chipset, the MB manufacturer could choose to route different numbers of address lines to the sockets, probably depending on whether the extra capacitive loading caused by a bigger memory module would have allowed it to function at the rated speed on that PCB. 64 MB would have been a typical maximum memory around 1998 (2 sockets for 32 MB SDRAM modules, on a MB with an AGP socket for the graphics card), so if the author would have had that year in mind, you would be right.