isusebj@gt-oscar.UUCP (Byron Jeff) (12/12/85)
[ damn you line eater! ]
My apologies if this article appears twice. I accidently mis-sent it the first time.
Does anyone have any hardware info on the 128? I've heard and read alot of
things and I'm wondering about the possibilities if they're true.
In lieu of any published info that I know of I'm posting some specific questions
that I have to the net.
1. Is there really an empty 32K rom socket in the machine?
If so how is it addressed?
Which of the CPU's in the machine can address it?
2. Is there a 6510 in the machine or does the 8502 (I think this is the name of the
128 mode CPU) do double duty (i.e. it's the CPU for 64 and 128 mode)? If it's used
in both modes is there any way to tweak it into accessing more memory in 64 mode?
(I know that the 64 mode is exactly like the c64 but there must be a way!)
3. What's the maximum memory the 8502 can access? I've heard reports up to 1M.
4. What chip refreshing the DRAMs in 128 mode w/ 80 columns? The VIC2 is off isn't it?
I ask because if the 8502 can access more and there's a refresh signal coming to
the expansion port (wishful thinking, I know) then extra memory (256K? 512? 1M!?)
could be added easily.
I'm assuming that the VIC2 does the refresh in 64 and 128 w/ 40 column modes and
the Z-80 in CP/M mode. Please correct me if I'm wrong.
5. Is it true that in 128 mode the OS and BASIC's address spaces are completely
separate from the 128K DRAM's? Is this also true of the mythic 32K rom space?
6. Is the shifting of the bits to the disk drive done in hardware (using the 6526
serial shift register) or in OS software (by banging out one bit at a time)? If
the hardware is used isn't it possible to speed up disk accesses? (The 6526
spec sheet in the c64 Programmers Guide states that the maximum shift rate is
clock/4. The clock rate in the 128 in 128 mode w/ 80 columns is 2Mhz. Disk
transfer rate of ~ 50K/sec (assuming the 1571 can read/write that fast) WOW!).
(I know this is wishful thinking. But what a wish!)
7. If the 1571 in CP/M mode can read Kaypro and Osborne (sp) disks why not IBM PC
format disks. Since the Amiga is using basically the same drive (different interface)
and they can read PC disks why can't the 1571. It seems to me that since the 128
has 2 (3?) CPUs in the box already another (specifically the 8088) couldn't really
hurt. (There goes that wishful thought again!)
8. Is there any info on the long awaited Programmers Reference Guide for the 128? Will
any (or all) of the goodies that I'm asking about above be documented?
Sorry for the long posting. Please E-mail all answers to me and when I get back
from Christmas vacation (January 4th) I'll summarize (sp) the responses I get to
the net.
--
Thanks,
Byron Jeff
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