Upgrade LC475 VRAM from 512k to 1Mb

[philallin]

I've been looking for a couple of 512kb VRAM memory sticks for ages to upgrade the video output of my LC475.

I came across these 2 months ago and got them shipped from the USA over to me in the UK.

512kb VRAM , 68pin, 80ns, Apple part no. 630-0045

These looked perfect for the job but when I put them in the LC475 it will not boot up.

I thought there may be a fault with the VRAM so I found a supply in Singapore, again got it shipped to the UK, put it in the LC475 only to be confronted with the same result.

I'm somewhat fustrated by this by now, but find another LC475 on Ebay (in the UK this time!) and got it shipped to me, but I'm really disapointed that this LC475 displays the same result as my original machine!

Can anybody here suggest what I may be doing wrong?

Thanks

 

[Unknown_K]

There are VRAMs which are 100ns that are labled LC only, I think it was just because of the slow speed (quadras need 80ns). I have a 68040/25 LC motherboard I can check it later to see what VRAM I am using in it (maxed out).

 

[philallin]

I have a 68040/25 LC motherboard I can check it later to see what VRAM I am using in it (maxed out).

Cheers Unknown K, any and all info on this would be much appreciated.

 

[equill]

Note: The LC 475 has 512K of VRAM installed via two 256kB VRAM SIMMs. Upgrading to 1MB of VRAM is accomplished by replacing those SIMMs with two 512kB, 68-pin, 80ns VRAM SIMMs.

This is the same memory-speed as that used by the DRAM.

de

 

[Charlieman]

From my personal notes:

"In theory, VRAM modules with similar characteristics (speed and size) should be interchangeable. The reality is that vintage Macs are much more sensitive to slight mismatches in VRAM modules than with system memory SIMMs and DIMMs. Mismatch symptoms include lines on the display, missing pixels or incorrect colours.

Apple were aware of this problem and ensured that official service or upgrade parts were the best fit for particular Mac models. For example, different service part numbers were listed for "identical" VRAM SIMMs for LCs, Quadras and 4*8 NuBus cards. Obtaining original service parts is unrealistic today, and you'll have to work around that limitation."

Alas the file that I need to check VRAM compatibility is in AppleWorks format, and AppleWorks is not installed on this Mac.

 

[Unknown_K]

I dug out the LC.

It has 2 pieces of Apple Computer 820-0605-a (printed on the board) with 4 Toshiba TC524258BJ-10 chips per SIMM.

Definatly not Quadra RAM nor 8.24 video card RAM (have some of that on a video card).

 

[philallin]

I dug out the LC.
It has 2 pieces of Apple Computer 820-0605-a (printed on the board) with 4 Toshiba TC524258BJ-10 chips per SIMM.

Definatly not Quadra RAM nor 8.24 video card RAM (have some of that on a video card).

820-0605-A same as the sticks that I have, but I have been researching and found something I didn't previously know.

The chips mounted onto each stick has a long number stamped across its centre, the end of the number is always in the format of -xx or -x where x or xx are digits. These digits refer to the speed of the chip i.e. -8 would indicate 80ns speed.

Of the 4 sticks of 512kb VRAM I have recently bought 2 have -10, one -8, and one -7.

I am guessing that as the LC475 requires a pair of 80ns VRAM sticks I currently do not have the correct specification.

Why would 3 different speed sticks all have the same part number stamped onto them????

Is Apple trying to confuse me or am I just missing something here?

 

[Unknown_K]

They could have used whatever was around that was as fast or faster then needed (but not slower).

I have seen video cards that had different chips and speeds before, but it is not common (they ran out of one batch and started using another in production).

If even one of those chips is 100NS then that is the fastest that module can go. I have never seen varying speeds in Apple VRAMS as of yet, and I snag any that come my way.

 

[equill]

... Of the 4 sticks of 512kb VRAM I have recently bought 2 have -10, one -8, and one -7.
I am guessing that as the LC475 requires a pair of 80ns VRAM sticks I currently do not have the correct specification ...

If, being of a tidy cast of mind, you used the pair of 100ns, they are too slow for the 475, no matter that the slower LC can use 100ns. You could hazard using the two faster cards, which would allow the the System to treat them both as 80ns, with a very good chance that they would work. (Ideally, you will use two completely-matched VRAM cards of 80ns or faster.) If that does not get you going, it is more than possible that you have a separate problem from that of the VRAM specification, relating to the VRAM slots, your PRAM battery (because the video characteristics for the display last used are stored there for the startup process), and so on.

de

 

[philallin]

... Of the 4 sticks of 512kb VRAM I have recently bought 2 have -10, one -8, and one -7.
I am guessing that as the LC475 requires a pair of 80ns VRAM sticks I currently do not have the correct specification ...

If, being of a tidy cast of mind, you used the pair of 100ns, they are too slow for the 475, no matter that the slower LC can use 100ns. You could hazard using the two faster cards, which would allow the the System to treat them both as 80ns, with a very good chance that they would work. (Ideally, you will use two completely-matched VRAM cards of 80ns or faster.) If that does not get you going, it is more than possible that you have a separate problem from that of the VRAM specification, relating to the VRAM slots, your PRAM battery (because the video characteristics are stored there for the startup process), and so on.

de

I've tried every combination possible from the 4 sticks of VRAM in 2 different LC475s. Both machines work perfectly with the smaller 256kb sticks installed.

One of the machines does have a dead PRAM battery and I have to 'jump start' it each time I power it up, however the second machine has a good battery that was new less than 6 months ago.

I'm guessing that the -8 and -7 set of sticks should work in the machine but it seems I'm out of luck!

It has been mentioned in an earlier post to this thread that the VRAM should be installed as a matched pair.....I might have to buy yet more VRAM, I've spend more on shipping alone for the last 2 sets than the LC475 is worth but it's become something of a quest for me to actually make it work now!

If anybody reading this has a pair of 512kb sticks I can buy that will work in this machine please drop me a line..

Thanks to everybody who has posted so far to try and help, all of your time, effort and knowledge is much appreciated.

Phil

 

[Flash!]

I was just digging thru my stuff to find my 475's and a bunch of VRAM to play with when I realised that I'd already given them away! To a good home of course, but now I need to get me another 475 - I love those machines

I don't remember having any VRAM type problems coz those Macs are fairly bullet proof. Maybe I was lucky with the VRAM speeds because I certainly never checked the label!!! Given that you're testing on two Mac's and getting the same results on both suggests to me that there's something up with your VRAM (ha! I trust a 475 board more than a stick of VRAM aquired out of singapore ) Possibly you could check your VRAM in another Mac which has only one VRAM slot (like a LCII), or post your stick to someone else to test.

 

[JRL]

Sorry for reviving this board, but I have a question:

Are these VRAM sticks suitable in a Macintosh LC or are they strictly for video cards?