Port-vax archive

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Old Index]

Re: /etc/disktab on vax

On Tue, Jul 3, 2012 at 8:54 PM, Dave McGuire <mcguire%neurotica.com@localhost> 
> On 07/03/2012 07:52 PM, ..I'd rather be coding ASM! wrote:
>>>  It's not that the Z80 "requires a 4x clock", but four T-states (clock
>>> cycles) make up one machine cycle.  Instructions take anywhere from one
>>> to several machine cycles to execute, depending on the instruction.
>> This is pretty much my recollection. My Zeta system I knocked up
>> recently as part of the N8VEM project can have usually 6-20Mhz
>> oscillators assuming you have correct divider crystal for the disk
>> controller (FCD266). At 20Mhz, the thing goes like stink compared to my
>> spectrum. Decompresing 128kb via UNARC.COM is perhaps 6-7 seconds.
>> Spectrum+3 doing the same deal is around 40 seconds and the C128Dcr
>> rumbles in at around 2min 10s because the Z80 is running effectively at
>> 2Mhz becuase it shares the bus with the MOS6502 derivative. Old
>> communist UB880-D (Z80 clone) at 2mhz takes ~4 minutes (I wandered off
>> to make a cuppa).
>   Jeeze!  Neat stuff though.
>> I was talking more "higher level". Have you guys checked out the Zilog
>> ez80's? They don't support the full z80 ISA but that can be
>> micro-coded/patched pretty simply. I've seen one project that ran a port
>> of CP/M 2.2C and ZSYS. I don't care how much emulation of a couple of
>> missing instructions it has to do, but they run at 50Mhz and have a full
>> 4x4x4 pipeline. That'd be 'quick' in my books.
>   I've done a few commercial embedded projects with the eZ80F91.  A
> 50MHz Z80 is a BEAST.  I enjoyed working with it.
>   I abandoned it a couple of years ago in favor of ARM7 due to far
> better tools and chip availability.  Zilog's management is nearly as
> clueless as SGI's!
>                -Dave
> --
> Dave McGuire, AK4HZ
> New Kensington, PA

Actually Dave SGI was the worst case scenario at work for computer
companies. Whereas the one for Z80, Zilog was practically nonexistent.
Which is next to that.

Ideally the biggest problem for the Z80 is that it needed a command
processor who understood it. CP/M was written for the 8080. Running it
on the Z80 only made use of the original 8080 instructions. About the
time Ciarcia was promoting the Z180, someone announced a replacement
command processor who'd make use of the entire instruction set.

Annoying isn't it.
Gregg C Levine gregg.drwho8%gmail.com@localhost
"This signature fought the Time Wars, time and again."

Home | Main Index | Thread Index | Old Index