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 piggy backing video card ram View next topic
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Joined: 27 Jan 2007
Posts: 274
Location: USA

PostPosted: Fri Dec 17, 2010 8:41 am Reply with quoteBack to top

Ive been hunting for an ati mach64 for a long time, eversince my 4mb one died of severe corrosion. Currently using a diamond speedstar 64 with 2mb ram, its cirruslogic gd5434 based. I have read 2 articles which leads me to believe its possible to piggyback 4 more memory chips to double the ram, first was an article about a 1mb MCA video card with this chipset being doubled to 2mb by piggybacking and connecting pin 14 on the ram to pin 141 on the vpu, with a 22ohm resister inbetween. the second was a spec sheet for this chipset which says it will support 1,2 and 4mbs. As for getting the parts, i got a generic pci vga card with this chipset, plus many early 90's pci video cards. I do know that adding memory will just increase colordeph and resolution and not boost preformance, which in my case will be good as its primarly used for irc/light web browsing/image viewing under windows at 1024x768 @ 16bit. this card can do 1280x1024 at 256 colors, but i dont gots a monitor that supports anything higher than 1168x864. this is just a thought in the back of my head since it seems like finding an ATI mach64 that can use my 2mb upgrade module is like finding the only cute virgin at my old highschool(50% of the school students had STDs).
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Joined: 19 Apr 2006
Posts: 261
Location: WisConSin

PostPosted: Mon Dec 27, 2010 11:23 pm Reply with quoteBack to top

Seems its a tad complex to piggyback and add capacity.

From memory you need the pinout of the ram modules.

Low density modules will not use one of the enable pins

So as an example your last memory address pinon the chip for example is pin 20 but the low density module only uses to pin 19, thus
when you piggyback you have to rewire the pin 19 on one of the modules to pin 20 so it is enabled on the top half.

Next a video card won't just use 2mb of ram if you put it there, the card would have to have come optionally with that amount of ram and possibly might need some rejumpering to "see" and use the memory.

Occasionally you need to flash the bios or update the bios to use it because if it was never coded to use that amount it just won't see it.

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