ee161bep@sdcc3.UUCP (Paul Van de Graaf) (08/19/85)
After studying the memory map of the Amiga in the recent Byte article, I'm even more confused about what the Amiga architecture looks like, and why! It seems (from what I read in a recent posting) that the low 256k of memory is organized as 128k by 16 words, or maybe even 64k by 32 using some sort of interleaving scheme. Some weirdness must be going on, to allow the 3 other processors to access memory while only slowing the 68k down from 7.8 mhz to 7.0 mhz with DMA on (THEIR figures not MINE, no flames!). Did you notice that the co-processors can only access the low 512k page of memory? Shades of the Zero Page addressing of the PDP8 and 6502! A hi-res 16 color interlaced screen mode takes up about 64k of memory, so there's room for 4 or 8 screens in a 256k or 512k machine. I hope that's enough to support fast animation with page-flipping (ready for computer video cartoons?). I guess it's a pretty good tradeoff though. Another mystery... where does the ROM / Write-able Control Store / Neatest Kludge West of the Pecos, fit into the memory map? For some reason there's a 1.5 mb "hole" in memory from 80000 - 1FFFFF with "reserved for future expansion" over it. Is this where the Write-able Control Store (WCS) resides? This hole makes a mess of memory; if they left it out they would have had a possible 10 mb of contiguous memory (put THAT in your Mac and smoke it). When will people learn to put the RAM down low where it belongs, the ROM above it, and the I/O at either the top or the middle? Ah well, boys will be boys... How big is that WCS gonna be anyway? I'd be surprised if it's less than 128k given the hype Amiga Dos/Intuition is getting, more likely 256k or so. Sounds like a loooong boot. I'm sure people won't be bother to power down their Amigas (Amigos? Amigi? Amigee? Amigaxen?) unless they REALLLY have to. Creative Computing (well, it was either that or PC World when Computers & Electronics bit the dust) said that a version of Marble Madness will be available for the Amiga. Could this mean that Atari Games used the Amiga chipset in the coin op unit? If you think about it, this seems quite reasonable. What with Tramiel's lawsuit against Commodore over the chipset and all. The graphics and sound capabilities of the machine are definitely similar to the Amiga. You may have played with a dedicated Amiga and didn't even know it! Sorry if I'm going too long or being too flip about the subject, but I'm frustrated with the hype-sheet documentation I'm getting from the magazines. Can anyone doing development on the Amiga give better info? The machine's public now, don't hide hide behind your non-disclosure agreement. -------------------------------------------------------------------------------- | "I speak of none other than the microprocessor to come after me... A micro- | | processor whose merest operating parameters I am not worthy of computing. | | And yet I will... I speak of the iAPX-386!" - an Intel 80286 workstation. | | | | With apologies to "Deep Thought", of The Hitchhiker's Guide to the Galaxy. | |==============================================================================| | Paul van de Graaf sdcsvax!sdcc3!ee161bep U. C. San Diego | --------------------------------------------------------------------------------
csc@watmath.UUCP (Jan Gray) (08/24/85)
In article <2965@sdcc3.UUCP> ee161bep@sdcc3.UUCP (Paul van de Graaf) writes: >A hi-res 16 color interlaced screen >mode takes up about 64k of memory, so there's room for 4 or 8 screens in a >256k or 512k machine. 16 colours == 4 bits == 1/2 byte/pixel 640 x 400 pixels x 1/2 byte/pixel == 128000 bytes ....................................so there's room for 2 or 4 screens in a 256K or 512K machine. Jan Gray
sambo@ukma.UUCP (Father of micro-S) (08/25/85)
In article <2965@sdcc3.UUCP> ee161bep@sdcc3.UUCP (Paul van de Graaf) writes: >Amigas (Amigos? Amigi? Amigee? Amigaxen?) Given that amiga is a word in Spanish meaning "female friend," the plural form would be amigas. ----------------------------------------- Samuel A. Figueroa, Dept. of CS, Univ. of KY, Lexington, KY 40506-0027 ARPA: ukma!sambo<@ANL-MCS>, or sambo%ukma.uucp@anl-mcs.arpa, or even anlams!ukma!sambo@ucbvax.arpa UUCP: {ucbvax,unmvax,boulder,oddjob}!anlams!ukma!sambo, or cbosgd!ukma!sambo "Micro-S is great, if only people would start using it."