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Memory Speed Requirements for IBM 51x0 series?

T-Squared

T-Squared

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I'm just trying to figure out what speed of memory I need for my Sanyo MBC-775 (5160 clone) system, just to be sure it won't conflict or brick my system. (The bad memory I have already does that... >.>) I'm thinking that everything to make the 640k memory upgrade work is already in place, just that the memory I bought is not good enough (since my Macintosh 128k catches it in the startup test, and I need some also for that system).

The slowest I have found from Unicorn Electronics is 150ns. Are any IBM/clone systems sensitive to speed?
 
5mhz - 200ns (5150, 5160, 5155 here)
8mhz - 150ns (5170 here)
10mhz - 120ns

Those are minimum specs, i.e. 120ns will work just fine in 5160 and 5170. But 200ns is only going to work in 5150/5160.

You can use different brands and mix and match speeds, as long as they are at some minimum level or faster.

I have an 8MHz XT clone with 80ns 41256 chips, and it works fine. But you have to check each chip individually. I bought 40 41256 chips from ebay, and 3 of them where defective.
 
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One of my turbo XT systems that runs at 10Mhz had 120ns 41256 chips (for the first 2x256K banks) and 150ns 4164 chips (for the remaining 2x64K banks). To the best of my knowledge the system was only ever sold in a 640K configuration, so it's possible that it was actually set up that way from the factory... it passes every memory test I can throw at it.
 
Some factors:

* Sometimes, to satisfy supply requirements for a chip rated at a particular speed, the chip maker stamped a faster rated chip at the speed required for supply.
* Some systems may be using wait states for RAM operations, allowing the use of slower-than-normal RAM.
 
Yes, in the Macintosh 128k that I have. It's one of the later models with the 128k jumper and the 512k capacitor, resistors, and multiplexer IC PCB footprints. Any mixture of the current 41256 chips that I have showed a corrupted screen with a staticky startup noise. (rather than the bell tone it's supposed to output.)

Like I said in another topic, I'm thinking that the Sanyo MBC-775 is actually in ready condition. It's just that the memory chips are bad and will not allow the system to start up. (Much like the Macintosh, it has extra footprints; for an extra 158, a 139, and a 280 parity generator.)
 
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T-Squared said:
Yes, in the Macintosh 128k that I have. It's one of the later models with the 128k jumper and the 512k capacitor, resistors, and multiplexer IC PCB footprints. Any mixture of them showed a corrupted screen with a staticky startup noise. (rather than the bell tone it's supposed to output.)
Click to expand...

I meant a machine that didn't rely on modifications you've done, IE, you've seen it working with your own eyes with that type of chip installed. (Or, conversely, you've borrowed working chips from a machine that meets those conditions and put them in that Macintosh to prove that it's not a problem with your modifications, it runs with a known good set.)

Like I said in another topic, I'm thinking that the Sanyo MBC-775 is actually in ready condition. It's just that the memory chips are bad and will not allow the system to start up. (Much like the Macintosh, it has extra footprints; for an extra 158, a 139, and a 280 parity generator.)
Click to expand...

It's been a while since I looked at that thread, but my impression was there definitely could be some hanging chads.
 
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