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68-pin VRAM SIMM “shortage”?


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I’ve decided to start upgrading all of my LC class machines and I went onto eBay to source RAM and VRAM. I had previously bought 512kb VRAM SIMMs without issue for about $30 USD each. 
 

Turns out there are none to be found. Last ones sold were a couple here and there in the last two months and prior to that December when MemoryX was selling theirs. I should have bought a large quantity before they closed down. How unfortunate. 
 

Does anyone here have a source of 512kb (80ns preferred) VRAM SIMMs?

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I'm on the lookout for some VRAM too, it'd be a shame if the well's dried up. Makes me wonder if it's possible for someone to perhaps make reproduction sticks? We've seen new IIfx RAM, I wonder if the VRAM uses relatively special memory chips, or if commonly available ones would work.

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It seems 256kb VRAM is presently plentiful and relatively cheap. I bought 6 from a seller in the UK for an average of $12 USD each with shipping and they all worked and looked great. I have since ordered another 12 to have on hand. 
 

I have resorted to buying untested logic boards with the 512kb VRAM SIMMs on the boards. It’s reasonably economical. A bare untested LC board is usually about $40 which is only $10 more than the VRAM were selling for. I also picked up a Performa 600 board with two of the 512kb VRAM for $85. 
 

If someone can’t source any more or build any these SIMMs will become very expensive!

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MemoryX had some... had :(

 

I had a time even finding the later PowerMac 1MB modules, eventually just lucking out on ebay: two NOS kensington sticks for like $7 each.

 

One of the reasons I gambled on a Quadra 700 (which did have some battery damage that I repaired), is because I could see from the photos it had all 6 slots filled.

 

20 hours ago, ArmorAlley said:

I wonder now if we (the collecting/hoarding community) are the primary holder of VRAM.

I've thought along the very same lines.

 

I wonder though with the vintage  committing communities bring what they are (across the board), and especially what I've seen here since joining, if the DIY/repro route is more than viable, as mentioned above.

 

I mean, if there are trays of DayStar ASICs to be found, there's definitely got to be some in-spec VRAM

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20 hours ago, maceffects said:

Anyone happen to have chip information handy?  I can look it up and see if I can do a run of 100.


I can send you pictures of the various modules I have with close ups if you want. 
 

It seems to me the 256kb SIMMs use 2x 128kb chips and the 512kb generally just use 4 of them. There are often other components on the 512kb ones like resisters and possibly capacitors.

 

I know there are issues with the speed of the chips. Older LC Macs might not like VRAM faster than 100ns, as evidenced by an Apple TSB about it in 1992. 
 

The Quadra and LC475 require 80ns VRAM. Over clocking one of these sometimes needs 70ns. I don’t know if 70ns works just fine in an otherwise normal 040 Mac. I have some I can double check. 
 

Let me know what you need. I’d be happy to buy in to a large supply to help make the run of them sustainable to you. I could easily use 25-30 of these SIMMs myself. 

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19 hours ago, MrFahrenheit said:


I can send you pictures of the various modules I have with close ups if you want. 
 

It seems to me the 256kb SIMMs use 2x 128kb chips and the 512kb generally just use 4 of them. There are often other components on the 512kb ones like resisters and possibly capacitors.

 

I know there are issues with the speed of the chips. Older LC Macs might not like VRAM faster than 100ns, as evidenced by an Apple TSB about it in 1992. 
 

The Quadra and LC475 require 80ns VRAM. Over clocking one of these sometimes needs 70ns. I don’t know if 70ns works just fine in an otherwise normal 040 Mac. I have some I can double check. 
 

Let me know what you need. I’d be happy to buy in to a large supply to help make the run of them sustainable to you. I could easily use 25-30 of these SIMMs myself. 

Sure that would be helpful, I put most of my stuff away in storage in preparation for the 45ft container coming from China on Monday.  So, I don't have easy access to check things myself, at least not for the next few weeks. If it's practical I'd love to make it happen.  I'm already working on 168pin 128mb 5v DIMMs.

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19 hours ago, maceffects said:

Sure that would be helpful, I put most of my stuff away in storage in preparation for the 45ft container coming from China on Monday.  So, I don't have easy access to check things myself, at least not for the next few weeks. If it's practical I'd love to make it happen.  I'm already working on 168pin 128mb 5v DIMMs.


Ok probably best to switch this to DM so we can exchange emails. 

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21 hours ago, MrFahrenheit said:


I know there are issues with the speed of the chips. Older LC Macs might not like VRAM faster than 100ns, as evidenced by an Apple TSB about it in 1992. 
 

The Quadra and LC475 require 80ns VRAM. Over clocking one of these sometimes needs 70ns. I don’t know if 70ns works just fine in an otherwise normal 040 Mac. I have some I can double check. 

Did you mean slower then 100ns (the higher the number the slower the chip)? The speed the chips run at is set by the motherboard and you will have issues with VRAM that is specced to run slower then what the motherboard wants.

 

Its just like regular ram that will happily run slower then its max speed. 

 

512MB VRAM has been harder to source then 256K modules for a very long time. I remember trading 4 x 512K VRAM a long time ago for a Q950 CDROM bezel to a guy with a Q700 over a decade ago.

 

If you can source chips reworking 256K modules would probably be more economical then making new ones.

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20 hours ago, Unknown_K said:

If you can source chips reworking 256K modules would probably be more economical then making new ones.

 

Maybe for just a few, but PCBs are so cheap and let you skip the time it takes to remove the old chips and clean them up, plus it leaves more 256KB VRAM SIMMs in the world.

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21 hours ago, Unknown_K said:

Did you mean slower then 100ns (the higher the number the slower the chip)? The speed the chips run at is set by the motherboard and you will have issues with VRAM that is specced to run slower then what the motherboard wants.

 

Its just like regular ram that will happily run slower then its max speed. 

 

512MB VRAM has been harder to source then 256K modules for a very long time. I remember trading 4 x 512K VRAM a long time ago for a Q950 CDROM bezel to a guy with a Q700 over a decade ago.

 

If you can source chips reworking 256K modules would probably be more economical then making new ones.


I do know that the lower the number the faster the chips, the higher number the slower they are. 
 

There is something about these VRAM modules and using them in different Macintosh computers. 
 

You will find here:

https://tidbits.com/1992/08/24/vram-problems/
A reference to quotes from Apple where it is mentioned you should match the speed of VRAM to a particular model. 
 

Using faster VRAM in an LC can cause the machine to have a strip of missing or incorrectly colored pixels. Using slower VRAM on a Quadra could cause pixels to drop out in the image. 
 

From what I have in my hands, 512kb VRAM SIMMs are all 4 chip and 256kb are 2 chip. The specs of the chips themselves seems to be similar or the same. Leading me to believe you can’t just rework 256kb VRAM SIMMs into 512kb ones you need to build a simm board with 4 sockets. Technically you could desolder the chips from a 256kb SIMM and solder them onto a new 4 socket SIMM but that’s likely not worth it. 

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19 hours ago, MrFahrenheit said:

From what I have in my hands, 512kb VRAM SIMMs are all 4 chip and 256kb are 2 chip. The specs of the chips themselves seems to be similar or the same. Leading me to believe you can’t just rework 256kb VRAM SIMMs into 512kb ones you need to build a simm board with 4 sockets. Technically you could desolder the chips from a 256kb SIMM and solder them onto a new 4 socket SIMM but that’s likely not worth it. 

 

I'm seeing some images online of 2 chip 512KB SIMMs claimed to be pulled from Macs, so it definitely sounds possible, but it's also possible not all models support them.

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20 hours ago, SuperSVGA said:

 

I'm seeing some images online of 2 chip 512KB SIMMs claimed to be pulled from Macs, so it definitely sounds possible, but it's also possible not all models support them.

 

Can you link to those?  I also did a search, and any of the two chip SIMM boards I found that claimed to be 512KB ended up having 2x 128KB chips on them (meaning they were 256KB simms).

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19 hours ago, MrFahrenheit said:

 

Can you link to those?  I also did a search, and any of the two chip SIMM boards I found that claimed to be 512KB ended up having 2x 128KB chips on them (meaning they were 256KB simms).

Here's one I found claiming to be from a Mystic Color Classic: https://www.worthpoint.com/worthopedia/512kb-68pin-70ns-vram-simm-selected-1806282637

They have two TC528257J-70, which should be 2Mb/256Kx8 70ns chips.

 

Here's another http://web.ncf.ca/bj151/mac/mac-ram/68pin-512k-vram-simm.html

This one is similar but with 80ns chips.

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I just took a look at some VRAM I have in a bag and most of it is Apple made except for one. One pulled from an LC has a sticker on the back saying LC only but it is the same as some other ones I have that say 670-0629 on the board and 4.8 display VRAM printed on them. Some of those chips are 100ns and some are 80ns (one has a 630-0044 sticker on it and that one is 80ns).

 

I also have a couple 4 chip 80ns SIMMs marked 630-0045 with a sticker and I believe those are 512KB VRAM.

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I make these with NOS ICs.  $26/ea shipped to the US.

Edit: These are 256KB

 

This same PCB accepts four ICs on the opposite side for 512K, so if there is demand, I can have them made quickly.  The chips for the two module sizes have different row/column dimensions, so a 512K module cannot be made with chips from a 256K module.

vram.thumb.png.eb149afd6551abdb2eaa4fbf3cdc1182.png

Edited by ymk
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20 hours ago, ymk said:

I make these with NOS ICs.  $26/ea shipped to the US.

Edit: These are 256KB

 

This same PCB accepts four ICs on the opposite side for 512K, so if there is demand, I can have them made quickly.  The chips for the two module sizes have different row/column dimensions, so a 512K module cannot be made with chips from a 256K module.

vram.thumb.png.eb149afd6551abdb2eaa4fbf3cdc1182.png

How much would a 512k VRAM stick cost if 256k would go for $26? Interested in upgrading my LC so I can add the 256k to my recent Quadra 700 acquisition.

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19 hours ago, Architecture said:

How much would a 512k VRAM stick cost if 256k would go for $26? Interested in upgrading my LC so I can add the 256k to my recent Quadra 700 acquisition.


I’ve sourcing my 256kb VRAM from UK for $12 USD each including shipping (when buying 10 pieces). 

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On 2/26/2021 at 4:58 PM, Unknown_K said:

I remember trading 4 x 512K VRAM a long time ago for a Q950 CDROM bezel to a guy with a Q700 over a decade ago.

 

Hopefully he didn't expect to get 2 MB (+512k on board) out of that config:lol:The 700, 900, and 950 can "use" 512k modules, but will only read 256k of reach one.

 

According to the Apple Memory Guide, very few of the Quadra/Centris line utilize 512k modules, but a IIvx/vi can?? 605/475 also do. I read somewhere this was a limitation within the ROM, but you'd think as the 90s went on higher on-board color density at "desktop publishing" resolutions might've been desired, especially on the flagship or higher end machines that could handle it... But maybe there's another technical limit there I'm not considering.

 

The Wombat boards (650/800) can't use them, even an 840av can't use them... And that was primo, tip top definition of Flagship Macintosh.

 

The utilization... It's just baffling to mme but again, if there's a limit, like there wasn't a point to having 4 MB on-board, I'd like to know.

 

I mean Radius and RasterOps were definitely in that ballpark and beyond with their top model NuBus cards.

Edited by jessenator
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