ericm@sage.cc.purdue.edu (Eric Mulholland) (11/03/90)
This has been brought up in the past but I don't remember a definate
answer to it. I know that memory above 4 megs is not DMA accessable.
My question is it 4 megs TOTAL memory or 4 megs of EXPANDED memory?
I have a 4 meg rancard (RamPRO IIgs) and I'm curious to wether the top
256K of ram on it is DMA or not. As you guessed, I have a rom 1 IIgs.
--
____
Y_,_|[]| Eric Mulholland
{|_|_|__| ericm@sage.cc.purdue.edu
//oo--OO ...!pur-ee!sage.cc!ericmjb10320@uxa.cso.uiuc.edu (Desdinova) (11/03/90)
In article <4866@sage.cc.purdue.edu> ericm@sage.cc.purdue.edu (Eric Mulholland) writes: > > This has been brought up in the past but I don't remember a definate >answer to it. I know that memory above 4 megs is not DMA accessable. >My question is it 4 megs TOTAL memory or 4 megs of EXPANDED memory? >I have a 4 meg rancard (RamPRO IIgs) and I'm curious to wether the top >256K of ram on it is DMA or not. As you guessed, I have a rom 1 IIgs. The limit of memory expansion is based on one and only one thing- only four rows of RAM are directly supported by the IIgs and it's DMA scheme. Four rows = 1Meg with 256K chips, or 4Meg with 1Meg chips (SIMMs or what not). Designers wishing to go past the four row limit can decode the address lines themselves to get more than 4 rows, and by keeping track of the DMA bank can support DMA with this non-standard configuration. > Y_,_|[]| Eric Mulholland >{|_|_|__| ericm@sage.cc.purdue.edu >//oo--OO ...!pur-ee!sage.cc!ericm Cute! -- Jawaid Bazyar | Blondes in big black cars look better wearing Senior/Computer Engineering | their dark sunglasses at night. (unk. wierdo) jb10320@uxa.cso.uiuc.edu | The gin, the gin, glows in the Dark! Apple II Forever! | (B O'Cult) Comp.Sys.Apple2- Home of the Unofficial Apple II Developer Support Team (DST)
ericm@sage.cc.purdue.edu (Eric Mulholland) (11/04/90)
In article <1990Nov3.121558.7963@ux1.cso.uiuc.edu> jb10320@uxa.cso.uiuc.edu (Desdinova) writes: > The limit of memory expansion is based on one and only one thing- >only four rows of RAM are directly supported by the IIgs and it's >DMA scheme. Four rows = 1Meg with 256K chips, or 4Meg with 1Meg chips >(SIMMs or what not). My question is about DMA not amount of ram. Everyone says the GS can only handle 4 megs of DMA ram (8 megs total). I have a rom 1 GS (256K) and a 4 meg ramcard (supports DMA) thus giving me 4.25 megs of memory. Of this 4.25 megs, can DMA access all of it or is the last 256K on the ramcard non-DMA? -- ____ Y_,_|[]| Eric Mulholland {|_|_|__| ericm@sage.cc.purdue.edu //oo--OO ...!pur-ee!sage.cc!ericm
toddpw@nntp-server.caltech.edu (Todd P. Whitesel) (11/04/90)
ericm@sage.cc.purdue.edu (Eric Mulholland) writes: >Of this 4.25 megs, can DMA access all of it or is the last 256K on the >ramcard non-DMA? All of it. The DMA limit applies to expansion RAM size. Todd Whitesel toddpw @ tybalt.caltech.edu
MQUINN%UTCVM@PUCC.PRINCETON.EDU (11/04/90)
T .CIS.OHIO-STATE.EDU> On Sat, 3 Nov 90 12:15:58 GMT Desdinova said: > > The limit of memory expansion is based on one and only one thing- >only four rows of RAM are directly supported by the IIgs and it's >DMA scheme. Four rows = 1Meg with 256K chips, or 4Meg with 1Meg chips >(SIMMs or what not). So, I guess the answer to the question is that the 256k on board isn't DMA compatible? Or is it, and only the first 3.75megs on a RAM card are DMA compatible? >-- >Jawaid Bazyar | Blondes in big black cars look better wearing >Senior/Computer Engineering | their dark sunglasses at night. (unk. wierdo) >jb10320@uxa.cso.uiuc.edu | The gin, the gin, glows in the Dark! > Apple II Forever! | (B O'Cult) >Comp.Sys.Apple2- Home of the Unofficial Apple II Developer Support Team (DST) ____________________________________________________________________ | | | | This is your brain... | BITNET-- mquinn@utcvm | | This is your brain on drugs... | pro-line: | | This is your brain on frog licking.| mquinn@pro-gsplus.cts.com | |____________________________________|_______________________________|
jb10320@uxa.cso.uiuc.edu (Desdinova) (11/05/90)
In article <9011040741.AA24846@apple.com> MQUINN%UTCVM@PUCC.PRINCETON.EDU writes: >T > .CIS.OHIO-STATE.EDU> > >On Sat, 3 Nov 90 12:15:58 GMT Desdinova said: >> >> The limit of memory expansion is based on one and only one thing- >>only four rows of RAM are directly supported by the IIgs and it's >>DMA scheme. Four rows = 1Meg with 256K chips, or 4Meg with 1Meg chips >>(SIMMs or what not). > >So, I guess the answer to the question is that the 256k on board isn't DMA >compatible? Or is it, and only the first 3.75megs on a RAM card are DMA >compatible? Oops, I blew it. All RAM on the motherboard is DMA compatible. RAM on a RAMcard is DMA compatible if it's designed as I said above (only 4 rows). With a ROM03 and a 4Meg card, you can have 5 meg of DMA compatible memory. >| This is your brain on frog licking.| mquinn@pro-gsplus.cts.com | Eh? -- Jawaid Bazyar | Blondes in big black cars look better wearing Senior/Computer Engineering | their dark sunglasses at night. (unk. wierdo) jb10320@uxa.cso.uiuc.edu | The gin, the gin, glows in the Dark! Apple II Forever! | (B O'Cult) Comp.Sys.Apple2- Home of the Unofficial Apple II Developer Support Team (DST)