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Re: Apple I schematics?
- Subject: Re: Apple I schematics?
- From: Patrick Schaefer <PSchaefer@epost.de>
- Date: Fri, 21 Dec 2001 02:04:53 +0100
- Newsgroups: comp.sys.apple2
- Organization: am Notebook
- References: <H29U7.144331$Ga5.23000866@typhoon.tampabay.rr.com> <9vrecd$5vk$2@nserve1.acs.ucalgary.ca> <3c228639_1@news.tm.net.my>
- Xref: archiver1.google.com comp.sys.apple2:15828
sfbong schrieb:
> 1. What are all these chips
> 2504 at D5
> 2519 at C3
> 2513 at D2
> DS0025 at terminal section.
U2504 and U2519 are PMOS shift registers, they form the display memory.
U2513 is a character generator. DS0025 generates the two-phase clock for
the PMOS devices.
> 2 Can DM8097 be replaced by 74LS367 or 74LS245?
Yes. You could use a '367.
> 3. If I replace all the DRAM with a 6264 and remove the 2 multiplexers B5 &
> B6. Would it affect the working of the video circuitry ? Is the video
> display memory inside the main RAM ?
No. The video circuitry is completely independent and uses a
Centronics-like interface protocol.
> 4. Can the 6820 be replaced by 6821 ?
Yes.
> 5. Are the 2 PROM chips in the cassette interface the same chips as in the
> processor section A1 & A2 ?
No. The two proms on the CPU board contain the Monitor, the proms on the
cassette board contain a cassette driver routine.
Patrick