25 Jan
2008
25 Jan
'08
11:12 p.m.
[HP150-II 8087 upgrade]
Hmm just how is it disabled? Someone wanted to add an
According to the Techref....
There's a D-type filp-flop ('74) driving the HOLD input on the mainboard
8088. When you plug the coprocessor card into its special connector, the
SET input of that flip-flop is grounded by the corprocessor board, thus
forcing the processor into the hold mode (normally used for DMA, of
course). There's also a link on the mainoard in series with the ALE
signal which you cut when you install the coprocessor board, since that
is one singal not tri-stated in hold mode.
8087 to a Peanut, and it made the most sense to plug
a
board (w/a *new* 8088) into the old 8088 socket.
If you're going to remove the original 8088, then there's no problem,
surely? As I menntioned, in the HP150-II, the cprocesor board plugs into
a special connecotor on the mainboard, not one of hte normal expanison
slots or anything like that.
-tony