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LaPorta

Soldering new vram onto Quadra 630 motherboard?

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Hi everyone,

 

It appears that to get the 1 MB of vram that the Quadra 630 has, they used 8 - 128k RAM chips soldered to the motherboard. Does anyone know of any pin-compatible RAM chips that may come in 512k size? Boosting the vram to 4 MB would be kind of cool.

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Look up the ICs, I'm pretty sure those are 128x4 DRAM ICs making up the 4MB of built-in system memory? My Q630 board is MIA ATM, so I can't check. What's the pincount/package type of that memory? Sounds like 4MB of soldered memory in Bank A in the Q605/LC475 from your description, which fits in with the 630's heritage.

 

The 6290 appears to use a pair higher density ICs (DRAM?) for its of 1MB VRAM. This pittance was standard from 630 through 6400 and was finally increased to a barely adequate (my opinion) 2MB in the 6500/TAM.

 

Dunno about piggybacking same/same ICs, but it would be interesting to see if addressing VRAM doubled in that manner might be a possibility?

 

Edited by Trash80toHP_Mini
the usual

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First i need to see if I can even get this sort of VRAM. All I'm looking for is enough to get thousands of colors at 800x600...the 1MB limits it to 256 at that resolution.

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it's a worthy experiment.  There's a good chance that the Valkyrie video controller won't address more than 1MB of VRAM, or that the address lines are not present, but who knows.  The Hardware developer note (http://mirror.informatimago.com/next/developer.apple.com/documentation/Hardware/Developer_Notes/Macintosh_CPUs-68K_Desktop/Mac_LC_630_Quadra_630.pdf) pg. 16, says that the Valkyrie is similar to the display portion of the MEMCjr in the Q605 (1MB limit) and the DAFB in the Q700 and Q900 (2 MB?).    The note also says that the video memory is plain old RAM, not any special dual ported RAM or such. 

 

Late edit:  and the note says there's 8MB of address space allocated to VRAM.   Doesn't mean much, but at least it's not limited to 1MB.  Figure 2-2, pg. 19.

 

One megabyte of memory, thirty-two bits wide, in 8 chips is made of 8 1Mbit chips which are each 4 bits wide.  So, 256K X 4 chips, X 8.   If you want to double that, then you need to find 512K X 4 chips.   The pinout will be standard.   256K means that there are 18 address bits, and at least 9 address pins on each chip (addresses are multiplexed, sent 1/2 at a time).   If there are only 9 address pins, then it can't be done, absent discovering an unused DRAM address pin on the Valkyrie chip.   512K X n memory chips require at least 10 address pins.

 

However, there is a tiny bit of hope, as the 256K chips could be addressed in an 8 X 10 or 10 X 8 pattern instead of 9 X 9, in which case 10 address pins would be present.

 

As someone else wrote, the first step should be to identify the VRAM chips and find a datasheet for them.

 

Oh, one last thing, memory capacities of chips seemed to always increase by factors of 4, so 512K X 4 chips may not exist.   You may have to go to 1M X 4.   That can still work with 10 address pins though, so if there are 10 the first hurdle is cleared.

 

It looks like I have a bunch of Oki MSM514400D 1M X 4 chips on hand, somewhere in the attic.    These are also what the super common 4MB 32 pin SIMM would have usually have built out of, so you can salvage them from those too.

 

Looking at the datasheet for the M2M514400, the chip has 20 pins in a 26 pin pattern.  I.e. There are two rows of pins with room for 13 pins, but the middle 3 pins in each row are omitted.

MSM514400E.pdf

Edited by trag

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LaPorta, any chance of taking some hi res pics of you logic board? Can't find mine and it's beginning to piss me off. It can't drive me crazy, but it could bring on an episode. :blink:

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I'm on call at the hospital...I can certainly get some for you tomorrow. I can also try this at any point: since I went with the Quadra 630 board for my custom machine, I have the Performa 630 board left over that I can experiment on.

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Hrmmm  .  .  .  does "DMA8-0" designations in the Q630 and PM5260 Block Diagrams differ from "A8-0" I've seen elsewhere?

 

Q630

Block_Diagram_Quadra630.thumb.JPG.ca0af043829ee1f1334883e015709f37.JPG

 

PM5260

Block_Diagram_PM5260.thumb.JPG.1a0002a39fd2a7838836c74fd8b78bb2.JPG

 

I'm wondering if the three bank setup of Video Memory could be problematic as it's tightly intertwined with the video input module's workings?

 

Quote

Display RAM
The display memory in the Macintosh LC 630 and Macintosh Quadra 630 computers
is separate from the main memory. To reduce the cost of the computer, the display
memory is implemented with DRAM devices instead of more expensive VRAM devices.
The display memory consists of 1 MB of 60 ns DRAM devices configured to make a 32-bit
data bus. The display memory cannot be expanded.
The display memory contains three separate frame buffers. The first frame buffer holds
the graphics data—the display that is generated by the computer. The other two frame
buffers hold video data from the video input module. The video data frame buffers are
used alternately: while one is supplying data to be sent to the video monitor, the other is
receiving the next frame of video input.
The display data generated by the computer can have pixel depths of 1, 2, 4, 8, or 16 bits
for monitors up to 640 by 480 pixels and 1, 2, 4, or 8 for larger monitors and the
800-by-600-pixel display on the multiscan monitor. Data from the video input module
is always stored and transferred at 16 bits per pixel. The video frame buffers support
live video in a 320-by-240-pixel frame at 30 frames per second.

 

Doesn't sound anywhere near as simple as adding a second VRAM SIMM to a 605 if you find DMA9.

Edited by Trash80toHP_Mini

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Thank you, that was what I was figuring from the traces on the board as well One would assume then 512k each. Now, finding possible replacements...

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Strange, I can't find the datasheet or spec on that DRAM IC. Seems strange that the 6290 would have a quartet of lower capacity chips than the 630? Is there another pair on the "solder side" of the board.

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It must be the 32bit/64bit bus width bump in that case.

 

edit: gotta come up with the datasheet for whatcha got there already to check the pinouts, if there's no room for that tenth bit, it's stacking, not replacement.

 

Given the tight integration of "video data frame buffers" in Valkyrie, I'm not even bettin' a nickel of finding that tenth bit. My bet would have to be on not being able to find A9 even on the second gen Valkyrie-AR on the Alchemy boards. :/

Edited by Trash80toHP_Mini

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