I wrote a 3458A NVRAM dumper based on Poul-Hennings work. It is included as part of John Miles' GPIBKIT package (from KE5FX.COM)... the program is called HP3458.CPP (and .exe) It can dump the cal nvram and/or the data nvrams. It outputs a binary file (or files) and also decodes and lists the calram data values and what they mean. Read the comments at the start of the cpp file for some more details.