Maximizing memory on my Centris 650 - will this work?

[1200XL M.U.L.E.]

I'd like to max out the RAM in my Centris 650 before I button up the case. From a little bit of research on the internet, I am thinking of buying two of these to get 128MB.

64MB (2X32MB) MEMORY 8X32 72PIN NON PARITY FPM 60NS 5V RAM SIMM | eBay

Part Number 16chip double sided FP mode SIMM. Manufacturer Third Party. Helpful Links.

www.ebay.com

I want to max out the RAM because I want to run a RAM disk. It sounds like the trade off is a longer boot time. That's OK. I'm not in any rush. If I were then I wouldn't be working with older machines.

Just wanted to check ... is that the good, right RAM for my Centris 650?

Thanks!

 

[sstaylor]

Those are the largest simms the 650 will accept, and the speed is plenty fast. Looks like you should be good to go.

 

[cheesestraws]

To add to that: MemoryMasters stuff is in my experience decently made, I've got a big stash of their SIMMs which work really well.

 

[beachycove]

Try the utility Maxima for your RAM disk.

 

[Phipli]

It is technically possible to use 4x64MB SIMMs. The stock limitation is 32MB per bank (I think that's the term), meaning if you can find dual bank 64MB SIMMs, you can get 256+8=264MB... but...

a) I'm not sure they exist
b) it takes a out 2 minutes to do the memory test
c) 128MB is already a huge amount of RAM for this era.

If money is no object, getting 128MB SIMMs is easier, and dual bank 128MB SIMMs are just recognised as dual bank 64MB SIMMs. You only get half the RAM you install, but it is easier than finding the correct 64MB SIMMs.

Ignore this post. Its just the pedant in me being frustrated by reading that 128+8 is the maximum

 

[Phipli]

<cough>
https://www.ebay.com/itm/175504191919</cough>

 

[Phipli]

Try the utility Maxima for your RAM disk.

How come vs the built in one? I only ever used Maxima in System 6?

 

[1200XL M.U.L.E.]

It is technically possible to use 4x64MB SIMMs. The stock limitation is 32MB per bank (I think that's the term), meaning if you can find dual bank 64MB SIMMs, you can get 256+8=264MB... but...

a) I'm not sure they exist
b) it takes a out 2 minutes to do the memory test
c) 128MB is already a huge amount of RAM for this era.

If money is no object, getting 128MB SIMMs is easier, and dual bank 128MB SIMMs are just recognised as dual bank 64MB SIMMs. You only get half the RAM you install, but it is easier than finding the correct 64MB SIMMs.

Ignore this post. Its just the pedant in me being frustrated by reading that 128+8 is the maximum

Wow, that's a lot to unpack!

Let me see if I understand this right.

The Apple-approved, or stock limit, is using four 32MB modules, 4 * 32MB = 128MB.

It is possible to use four 64MB modules, as long as they are in a dual bank configuration (vs. single bank, I assume?) and get even more memory capacity, 4 * 64MB = 256MB.

Finding these dual bank 64MB modules is difficult but finding dual bank 128MB modules is easier. The computer will accept them but only recognize 64MB of the 128MB in each module. That would still give me 4 * 64MB = 256MB.

The link above references 128MB dual bank memory from Memory Masters.

How do I recognize dual bank memory when shopping?

Should I be concerned with extra power draw or heat?

 

[Phipli]

How do I recognize dual bank memory when shopping?

Unless the listing makes it clear it seems difficult because its about how they're wired. Commonly, every second size was dual bank but there isn't a hard and fast rule. Sometimes you see single bank SIMM has empty chip footprints on one side I think? So 16 would be single, 32 dual - potentially the same board half and fully populated. 64, single, 128 dual. But... I haven't got many types of high capacity SIMMs to study.

Should I be concerned with extra power draw or heat?

I don't think so.

The link above references 128MB dual bank memory from Memory Masters.

I've bought similar parts in the past from the same seller. The 650 should also work with EDO, but I try to get FPM because it works with more different machines.

 

[Phipli]

This is my Centris 650. It only says Quadra 800 because I'd been messing with the machine ID resistors etc. on the board.

It says the OS is using all the memory because it booted in 24bit (32bit is needed to recognise more than 8MB) and I hadn't restarted it.

One thing! I was unable to overclock my machine to 40MHz with these RAM SIMMs. I suspect a timing issue. It was fine with 4x 32MB SIMMs I had.

 

[beachycove]

Maxima will do a fabulous job of managing a full-blown RAM disk on a Quadra with plenty of RAM. It works well with RAM compression, will back up to disk automatically on shutdown, and start up from said archive on booting. It’s a great utility. Spin down your mechanical drive in between.

A Q650 will run like greased lightning from a RAM disk, btw. Applications boot more or less instantaneously, things are extremely fluid, and the overall impression is rather like having an SSD installed — which in a manner of speaking you do.

 

[Phipli]

Maxima will do a fabulous job of managing a full-blown RAM disk on a Quadra with plenty of RAM. It works well with RAM compression, will back up to disk automatically on shutdown, and start up from said archive on booting. It’s a great utility. Spin down your mechanical drive in between.

A Q650 will run like greased lightning from a RAM disk, btw. Applications boot more or less instantaneously, things are extremely fluid, and the overall impression is rather like having an SSD installed — which in a manner of speaking you do.

Thank you, it sounds like a more feature rich implementation.

 

[1200XL M.U.L.E.]

Hmmm! This all sounds very enticing!

If I'm going to go down this rabbit hole then I want to go all in with four modules. Too bad the seller only has two and is listing this in British pounds.

Here are two listings for 128MB modules.

128MB 72 Pin FPM Memory SIMM 5V 60ns | eBay

Find many great new & used options and get the best deals for 128MB 72 Pin FPM Memory SIMM 5V 60ns at the best online prices at eBay! Free shipping for many products!

www.ebay.com

and

128MB FPM Parity 72pin SIMM 72p 16x4 ICs 60ns for Apple Performa 630CD | eBay

64 Mb Edo Ram for Macintosh Performa 6400/180. 1GB KIT ( 512MB x2) PC133 PC-133 RAM SDRAM for G3 Imac. 512mb pc133 Sodimm Plus 2X256MB 144 Polos PC100. 512mb pc133 Sodimm Plus 2X256MB 144 Broche PC100.

www.ebay.com

To my untrained eye, they are just 128MB modules. I'd grab four of the cheaper of the two, click them in, and hope to see 256MB.

What am I missing here?

 

[beachycove]

Help! memory expansion for Quadra 650

Hi dear friends! Please can you help me with the memory expansion for my Quadra 650? On ebay and other web marketplace I have found various offers for simms 72 pin and for “EDO” simms… This last type is compatible with my Quadra? 60ns, 70ns, 80ns?? I am quite confused… I ask to the experts for...

68kmla.org

Searching is a wonderful thing….

 

[Phipli]

What am I missing here?

The former is not as described, I previously contacted and told the seller and they told me that "it didn't matter". Given their casual attitude to specs, I wouldn't buy from them. Those chip part numbers are EDO not FPM memory.

The latter is parity RAM and not the same orgznisation (32x32).

 

[beachycove]

Further to my last contribution, search/ dig around on the forum for posts on the subject by Trag.

 

[Phipli]

listing this in British pounds.

Probably my fault, I'm in British pounds and shiny pennies.

 

[1200XL M.U.L.E.]

Further to my last contribution, search/ dig around on the forum for posts on the subject by Trag.

I did a search for "256mb 650" and not a whole lot popped up. Your post from 2012 is here.

https://68kmla.org/bb/index.php?threads/what-are-your-most-prized-machines-amp-why.26283/page-4#post-277145

Did the upgrade work for you?

 

[beachycove]

That was a long, long time ago! But Trag is yer man for knowledgeable input on this one.

My 650 is currently in storage, but I do seem to recall that those 64mb SIMMs didn’t work in it — they do work famously, however, in a Q605/
mystic Color Classic, which is nice. The 650 does nicely loaded with 32s, that I do know.

Mine, as I say, is currently inaccessible. I recently moved and downsized; the Mystic CC is one of a very few machines I still have to hand.

 

[1200XL M.U.L.E.]

Ohh!! I thought you meant "search by Tag" ... but Trag is a member here!

Noted.