22 Apr
2021
22 Apr
'21
4:53 p.m.
Dave McGuire <mcguire at neurotica.com> wrote:
On the 780 it's just microcode patches, on the 730 it's all of
microcode. (both as far as I can recall)
Dave's right - ALL the 730 microstore, including the code for the IDC and/or FPA if
you have them, is RAM. From power on a 730 takes about 15 minutes before it's even
ready to boot VMS; that's a consequence of loading all that code from a fairly slow
TU58. Don't know how long it takes an 8600, but at least it has the benefit of an
RL02 for the console media.
Most (I won't say "all"!) of the other VAXes had at least some chunk of
the microstore in ROM. Most of them had some sort of microcode patch mechanism that
allowed chunks of microcode to be loaded into RAM at power up time, but this was just a
fraction of the total microcode.
Idle curiosity makes me wonder about the V11/KA820-825 now. IT was like the 750 in that
the console functions were implemented in microcode (i.e. no front end) but it did have
console media in the form of an RX50. Can't remember if it actually loaded some
microcode patches from the diskette, like the 750 did with the TU58, or if all the V11
microcode was permanently buried in the chip.
Bob