Path: csiph.com!news.mixmin.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: D Finnigan Newsgroups: comp.sys.apple2 Subject: Re: How does the Apple IIGS emulate a =?UTF-8?B?SUllPw==?= Date: Tue, 20 Feb 2024 14:09:27 -0000 (UTC) Organization: Mac GUI Lines: 46 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Tue, 20 Feb 2024 14:09:27 -0000 (UTC) Injection-Info: dont-email.me; posting-host="781fa24aac46f8c4787789e353a69271"; logging-data="2673931"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+R6CHfvi1R4N7NVV6H9xLv" User-Agent: Mac GUI Usenet Cancel-Lock: sha1:2dWMkQjXx5kycdDP4VP+7z9Zqlc= In-Reply-To: Xref: csiph.com comp.sys.apple2:48868 Kent Dickey wrote: > In article , > D Finnigan wrote: >> >> >>Here's a reference to an October 1986 BYTE Magazine article about the Mega >>II: >>https://macgui.com/usenet/?group=1&id=3626 >> >> >>THE MEGA II >>The Mega II is a custom CMOS chip containing about 3000 gates and a >>2K-byte >>by 8 ROM (for the character generator). It replaces the following chips >>from >>the Apple IIe and IIe: char­acter generator ROMs for eight lan­guages. >>several TTL chips that per­form logic functions. and the MMU (memory >>management unit). IOU (in­put/output unit). TMG (timing genera­tor). and >>GLU >>(general logic unit) custom chips. >> >>In previous Apple II designs, the re­freshing of memory was tied directly >>to >>the Apple II video mode. The Mega II includes an 8-bit counter for >>refresh­ing the 128K bytes of (slow) memory associated with the Apple >>IIe/IIc model; it does five cycles of RAM refresh during the horizontal >>retrace of each video scan line and refreshes the 128K bytes of memory in >>3.25 milliseconds. By taking care of RAM refresh the Mega II chip opens >>the >>Apple II design to new video modes that were impossible before. > > I don't know the source of the above paragraph and what it's trying to > say, > but I do not believe it is correct. The source is the October 1986 BYTE Magazine article by Gregg Williams, senior technical editor at BYTE. It's on page 86 of the issue of BYTE magazine dated October 1986. -- ]DF$ The New Apple II User's Guide: https://macgui.com/newa2guide/