asd@mace.cc.purdue.edu (Kareth) (09/22/90)
Okay, maybe I misunderstand something, or remember something wrong, so just correct me if I'm wrong. But didn't there used to be 12 DMA channels on the NeXT Cube??? Now there are only 9! Only 8 on the slab. What happened to those 3 DMA channels? Where'd they go? Was something else done to make things work better? What's the deal? I'd think increasing the number of DMA channels would be what you would want to do, not decrease them. -k
rca@cs.brown.edu (Ronald C.F. Antony) (09/25/90)
In article <5593@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes: > >Okay, maybe I misunderstand something, or remember something wrong, so >just correct me if I'm wrong. > >But didn't there used to be 12 DMA channels on the NeXT Cube??? >Now there are only 9! Only 8 on the slab. What happened to those 3 DMA >channels? Good question. I guess the difference between the slab and the cube lies in the missing OD support for the slab. But what happened to the 3 others I can't tell. Ronald ------------------------------------------------------------------------------ "The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man." Bernhard Shaw | rca@cs.brown.edu or antony@browncog.bitnet
asd@mace.cc.purdue.edu (Kareth) (09/25/90)
In <50950@brunix.UUCP> rca@cs.brown.edu (Ronald C.F. Antony) writes: >In article <5593@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes: >> >>Okay, maybe I misunderstand something, or remember something wrong, so >>just correct me if I'm wrong. >> >>But didn't there used to be 12 DMA channels on the NeXT Cube??? >>Now there are only 9! Only 8 on the slab. What happened to those 3 DMA >>channels? >Good question. I guess the difference between the slab and the cube >lies in the missing OD support for the slab. But what happened to the >3 others I can't tell. Hmm, I wonder if it's bad form to answer my own question in a followup to my message. One of the guys here suggest that he believed that the missing channels were due to the fact that the MMU, FPU, and cache which are all on the 040 now. -k
phd_ivo@gsbacd.uchicago.edu (09/25/90)
******************************************************************** >Good question. I guess the difference between the slab and the cube >lies in the missing OD support for the slab. But what happened to the >3 others I can't tell. Good rumor has it that two of these were never used (i.e. they were for things like memory-to-memory DMA), and two DMAs controlling serial ports were combined into one (I believe they have redesigned the entire serial interface). As stated, the slab does not need OD DMA support, so it has one DMA fewer. /ivo welch ivo@next.agsm.ucla.edu
daveh@cbmvax.commodore.com (Dave Haynie) (09/26/90)
In article <5606@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes: >In <50950@brunix.UUCP> rca@cs.brown.edu (Ronald C.F. Antony) writes: >>In article <5593@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes: >>>But didn't there used to be 12 DMA channels on the NeXT Cube??? >>>Now there are only 9! Only 8 on the slab. What happened to those 3 DMA >>>channels? >>But what happened to the 3 others I can't tell. >One of the guys here suggest that he believed that the missing channels >were due to the fact that the MMU, FPU, and cache which are all on the >040 now. Nope, at least not by any proper definition of "DMA channel". The cache and MMU situation is identical for the 68030 and 68040 with the NeXT; in both cases, you have on-chip cache and MMU. As for the FPU, the 68882 follows a private, Motorola defined communication protocol with the 68030; no use for any DMA channel here. My uninformed guess would be that NeXT considered each empty expansion bus slot to be a separate DMA channel from their DMA controller's viewpoint. Since the "slab" doesn't have these slots, it would be missing 3 channels. But that's really just a guess... >-k -- Dave Haynie Commodore-Amiga (Amiga 3000) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Standing on the shoulders of giants leaves me cold -REM
cz@wheat-chex.ai.mit.edu (Christopher R Zach) (09/26/90)
Ok, here is a list of the old DMA channels (on the 68030 Next) 2 for the Ethernet (1 for sends, 1 for recieves) 1 for the SCSI port 1 for the optical disk 1 for BOTH serial ports (shared) 2 Display's sound (1 for sending, 1 for receiving) 1 for writing the video memory 1 for the DSP --- 10 Dma channels In addition, there were 2 others that were reserved for memory/memory transfers for a total of 12. As far as which one of the above 10 were axed, I don't know. Chris
asd@mace.cc.purdue.edu (Kareth) (09/26/90)
In <14638@cbmvax.commodore.com> daveh@cbmvax.commodore.com (Dave Haynie) writes: >In article <5606@mace.cc.purdue.edu> asd@mace.cc.purdue.edu (Kareth) writes: >>One of the guys here suggest that he believed that the missing channels >>were due to the fact that the MMU, FPU, and cache which are all on the >>040 now. >My uninformed guess would be that NeXT considered each empty expansion bus slot >to be a separate DMA channel from their DMA controller's viewpoint. Since the >"slab" doesn't have these slots, it would be missing 3 channels. But that's >really just a guess... Well, there are 4 missing in the slab. Your assumption doesn't hold much water because there are still 4 expansion slots (well, three, if you don't count the cpu slot), on the cube still, and yet there are 3 missing DMA channels? Thanks for trying, but no go. -k
fjs@nntp-server.caltech.edu (Fernando J. Selman) (09/26/90)
cz@wheat-chex.ai.mit.edu (Christopher R Zach) writes: >Ok, here is a list of the old DMA channels (on the 68030 Next) >2 for the Ethernet (1 for sends, 1 for recieves) >1 for the SCSI port >1 for the optical disk >1 for BOTH serial ports (shared) >2 Display's sound (1 for sending, 1 for receiving) >1 for writing the video memory >1 for the DSP >--- >10 Dma channels >In addition, there were 2 others that were reserved for memory/memory transfers >for a total of 12. As far as which one of the above 10 were axed, I don't know. > Chris You forgot the printer channel. With this your addition is correct. Did you use a Mac for the sum? - Fernando P.S. Could someone from NeXT enlighten us?