Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Rich Newsgroups: comp.os.linux.misc,alt.folklore.computers Subject: Re: The "Good" Old Days - Complete Specs for DX-10 Operating System Date: Thu, 3 Oct 2024 17:02:28 -0000 (UTC) Organization: A noiseless patient Spider Lines: 24 Message-ID: References: Injection-Date: Thu, 03 Oct 2024 19:02:28 +0200 (CEST) Injection-Info: dont-email.me; posting-host="d7cc519475b7ade4d97e2849328cf560"; logging-data="4007020"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19+kv2ot6rWRKDCKMUujluI" User-Agent: tin/2.6.1-20211226 ("Convalmore") (Linux/5.15.139 (x86_64)) Cancel-Lock: sha1:JClg6r7OAwU4I0KCLPaWEKQlz5I= Bytes: 2365 In comp.os.linux.misc Scott Alfter wrote: > In article , Rich wrote: >>In comp.os.linux.misc 186282@ud0s4.net <186283@ud0s4.net> wrote: >>> The 990 series used the TMS-9900 chip and near variants. This was an >>> odd chip - kept the CPU registers out in ordinary RAM and could >>> switch quickly between different sets of registers. At that time, >>> the external RAM and CPU kinda ran at the same speed so little was >>> lost putting the registers in RAM. >> >>The 6502 did something similar. It wasn't as far down the path as the >>TI chip, but page zero (first 256 bytes of ram) acted a lot like an >>'extended register file'. There were even addressing modes that used >>two consecutive bytes of "page zero" as a 16bit pointer into the rest >>of the RAM one's system had installed, > > ...and the 65816 (the 16-bit successor to the 6502 that was used in the > Apple IIGS) let you move what was now called the "direct page" anywhere in > the first 64K of memory. A new register for the purpose was added, along > with another one that allowed the stack to also be put anywhere in the first > 64K (vs. having it locked to page 1). Nice, I did not know that about the 65816. I do wonder why restrict it to only first 64K?