13 Jun
2013
13 Jun
'13
10:33 a.m.
On Jun 13, 2013, at 12:29 PM, Ethan Dicks <ethan.dicks at gmail.com> wrote:
On Thu, Jun 13, 2013 at 12:06 PM, David Riley
<fraveydank at gmail.com> wrote:
It would not be easy to accelerate without some really weird
bus synchronization logic, though since the RAM is built into
the daughterboard, it would be easier than otherwise. The
68010 also has a different stack frame format for some
exceptions (notably bus error), which might require some ROM
modifications; I don't know if you'd need ROM modifications
to support the SCSI chip (you certainly would at boot; you'd
probably need Plus ROMs at the very least).
Side topic: I recently got a 128k/512k logic board off eBay
with the RAM array desoldered (definitely desoldered,
not just never installed). Does anyone know if there's any
special reason for that (e.g. one of these daughterboards),
or is it more likely that someone just used it as a RAM
donor? Once I get the time (and an analog board, or work up
some substitute for one), I'll see if there's anything else
broken on board; I think I have substitutes for every chip
on there except the HALs, and I can make subs for those with
GALs).
- Dave
On Jun 13, 2013, at 11:47 AM, Ethan Dicks
<ethan.dicks at gmail.com> wrote:
I don't think you could easily accelerate an original Mac, and I agree
there is no crystal there. You _could_ install a 68010 (presuming there
are no MOVEcc instructions to trip it up, as there are in, for example,
AmigaDOS 1.1) but AFAIK, it's just there to make room on the
mainboard to plug in the expansion board (much like an IDE
interface product for the Amiga whose name escapes me). It is, presumably, some buffers, an addressing
PAL or two, and the
obviously visible SIMM sockets and NCR 5380 chip.
And the unmistakable gargantuan footprint of a 68000. What is
that one? A faster one, or a 68010? I don't see a clock
crystal anywhere on that board, so a faster one wouldn't make
a lot of sense.