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Re: Z-RAM card for Apple //c
- Subject: Re: Z-RAM card for Apple //c
- From: mjmahon@aol.com (Michael J. Mahon)
- Date: 22 Jan 2002 08:33:00 GMT
- Newsgroups: comp.sys.apple2
- Organization: AOL http://www.aol.com
- References: <a2iad2$ilt$1@niflheim.rutgers.edu>
- Xref: archiver1.google.com comp.sys.apple2:16732
Hank Levinson wrote:
>Applied Engineering used a Z-80 chip for its RAM-refresh circuitry on its //c
>RAM cards. The Z80 chip was not intended for CP/M use. It was a cheap way to
>refresh RAM. A.E. made other Z80 cards for the //c especially for CP/M use.
Actually, the Z-RAM Ultra 3 has a Z80 which is there for running CP/AM,
not for refreshing DRAM. In fact the Z-RAM Ultra 1 and 2 do not have
a Z80.
The Z80 does support DRAM refresh inherently, but then so does
the Apple II video refresh--which simultaneously accomplishes DRAM
refresh. This dual function is what accounts for the somewhat contorted
y-axis addressing in Apple II graphics.
-michael
Email: mjmahon@aol.com
Home page: http://members.aol.com/MJMahon/