#: 5272 S15/Hot Topics
    16-Jul-90  22:34:04
Sb: #5258-32 bit bus?
Fm: Frank Hogg 70310,317
To: Kevin Darling (UG Pres) 76703,4227 (X)

Kev

Good information... at last! I'm only trying to reduce the amount of calls 'I'
get by responding to the question. The question related to the 16 bit K-Bus vs
the 32 bit MM1 bus and why. I know why the K-Bus is 16 bits and now I know why
the MM1 has a 16/32 bit bus. Thank you. PS I'm glad they liked the way the TC9
works. Imitation is the best flattery... Now don't start with the TC70 vs MM1.
(heh heh)

As to your questions. #1 re the TC70 upgrading to a 68030. Not possible, we did
not design it that way nor have we ever claimed that capability. The K-Bus is
expandable by replacing single function cards (CPU's etc) with better ones ie:
replace a 68000 CPU with a 68030 CPU. The other bus cards would still be used.
The TC70 is a multi-function card and only one can reside on the bus at a time.
It would have to be removed to upgrade the system to a 68030 for example. All
multi-function cards are less expensive to build because they do not have the
added cost of the bus for each function but they have the disadvantage of
inflexibility. That's why we offer both options. Spend more and have
flexibility, spend less and have less flexibility. In any case other K-Bus
cards added to a TC70 system would work with any CPU/multifunction card so not
all would be lost. BTW I have no intention of doing a 'shared-RAM adaptor' for
the TC70. The TC9 does that and that is enough for now. I may change my mind
later but not for now.

#2 The 5% loss was total system thru-put in a real life situation. I'll see if
I can get the specifics from Dave about exactly how he arrived at those
figures. This was done when the 68030 board for the K-Bus was being designed
(6-8 months ago) and I don't recall the details. In one case a 68030 K-system
replaced a 68020 20x system and the thru-put doubled, the K-system was twice as
fast as the 20x. (the 20x has a 32 bit data bus) However there is more to
performance than data bus size etc. The whole system and all its parts
contribute or detract from the overall performance.

cont...