30p SIMMs aren't rocket science. Just like other SIMMs, they come in parity (3/9 chip) and non-parity (2/8 chip) versions and in sizes of 256kB, 1MB, 4MB and 16MB. Apparently these cards only support 1MB and 4MB SIMMs. Speeds are max speeds and are given in times, so lower is better. If the card requires 80ns, anything below that (70ns is very commons0 is fine to.

The SIMMs themselves don't care what kind of system they are used on, so 1 or 4MB SIMMs for MAC will work on PCs and probably this card too. I once had some 16MB 30p SIMMs that I used in a Mac SE-30 and a 486 PC. Would possibly give a kidney for 4x 16MB SIMMs again now 😉

You could probably use faster, saw a 4x4 set of 60nS

dionb wrote:

30p SIMMs aren't rocket science. Just like other SIMMs, they come in parity (3/9 chip) and non-parity (2/8 chip) versions and in sizes of 256kB, 1MB, 4MB and 16MB. Apparently these cards only support 1MB and 4MB SIMMs. Speeds are max speeds and are given in times, so lower is better. If the card requires 80ns, anything below that (70ns is very commons0 is fine to.

If the ratings are for max speeds, and lower is better than wouldn't faster RAM not be supported? I'm confused by this. Aside from the ns, it sounds like the most important thing is that it is parity (9 chip) since it specifies #Megx9.

Would possibly give a kidney for 4x 16MB SIMMs again now 😉

Why? Is SIMM expensive and rare now?

dionb wrote:

I once had some 16MB 30p SIMMs that I used in a Mac SE-30 and a 486 PC. Would possibly give a kidney for 4x 16MB SIMMs again now 😉

https://www.ebay.com/itm/150973316008
A kidney for $40US is cheap. ^.^

luckybob wrote:

dionb wrote:

I once had some 16MB 30p SIMMs that I used in a Mac SE-30 and a 486 PC. Would possibly give a kidney for 4x 16MB SIMMs again now 😉

https://www.ebay.com/itm/150973316008
A kidney for $40US is cheap. ^.^

Slightly cheaper listing:
https://www.ebay.com/itm/64MB-SET-OF-FOUR-16M … x9/352583195963

I highly recommend you get 9-chip memory. Although the 3-chip memory has parity and should be functionally identical, in practice 9-chip 30-pin SIMMs are a hell of a lot more compatible. I have a lot of motherboards and memory cards that don't function at all with the 3 chip stuff.

Anonymous Coward wrote:

I highly recommend you get 9-chip memory. Although the 3-chip memory has parity and should be functionally identical, in practice 9-chip 30-pin SIMMs are a hell of a lot more compatible. I have a lot of motherboards and memory cards that don't function at all with the 3 chip stuff.

Okay -- but is it really fine to use other speeds outside what the manual specifies? (80ns)

faster is always backwards compatible.

dionb wrote:

The SIMMs themselves don't care what kind of system they are used on, so 1 or 4MB SIMMs for MAC will work on PCs and probably this card too.

No. Macs used no parity.
You can use Mac SIMMs only if your BIOS provides an option to disable RAM parity checking.
[OT]
One of the reason why I hated Apple since they 1984 introduced the Mac.
Outside outrageously expensive, inside a closed system that used the lowliest crap made expensive by using castrated proprietary modification.
No memory parity protection. SCSI drives without ID jumpers. SATA drives without SMART. Brittlest low quality plastics. And if you want to get help/replacement for your flawed Mac, you must sign an NDA first...
[/OT]

infiniteclouds wrote:

[...]

If the ratings are for max speeds, and lower is better than wouldn't faster RAM not be supported? I'm confused by this.

SIMMs are basically dumb passive devices. They don't clock anything themselves, they are clocked at a certain speed by the memory controller. If they can handle the speed, it's fine, if not you lose data or crash. See it like a speed limit on a winding road- you don't *have* to drive at that speed, you can also go slower, but if you go faster you might not make the bend. Equally, sometimes the limits are set too low and you can easily drive a bit faster (overclocking). However 80ns isn't challenging, so no point in trying to overclock even slower modules. Just go for 80ns or slower. Once again, most 30p SIMMs tend to be 70ns and that wil work fine. 100ns might not.

Aside from the ns, it sounds like the most important thing is that it is parity (9 chip) since it specifies #Megx9.

Yes, this is a requirement for parity.

Would possibly give a kidney for 4x 16MB SIMMs again now 😉

Why? Is SIMM expensive and rare now?

Higher capacity 30p SIMMs are relatively rare and expensive - but less so in the US it seems than over here looking at those eBay listings.

infiniteclouds wrote:

Anonymous Coward wrote:

I highly recommend you get 9-chip memory. Although the 3-chip memory has parity and should be functionally identical, in practice 9-chip 30-pin SIMMs are a hell of a lot more compatible. I have a lot of motherboards and memory cards that don't function at all with the 3 chip stuff.

Okay -- but is it really fine to use other speeds outside what the manual specifies? (80ns)

Lower numbers fine (but unnecessary), higher bad.

retardware wrote:

No. Macs used no parity. You can use Mac SIMMs only if your BIOS provides an option to disable RAM parity checking. [OT] One of […]
Show full quote

dionb wrote:

The SIMMs themselves don't care what kind of system they are used on, so 1 or 4MB SIMMs for MAC will work on PCs and probably this card too.

No. Macs used no parity.
You can use Mac SIMMs only if your BIOS provides an option to disable RAM parity checking.
[OT]
One of the reason why I hated Apple since they 1984 introduced the Mac.
Outside outrageously expensive, inside a closed system that used the lowliest crap made expensive by using castrated proprietary modification.
No memory parity protection. SCSI drives without ID jumpers. SATA drives without SMART. Brittlest low quality plastics. And if you want to get help/replacement for your flawed Mac, you must sign an NDA first...
[/OT]

IIRC it varied from Mac to Mac. Take a look at the eBay listings linked to for "Mac" 16MB SIMMs above here. One's non-parity, the rest are all parity. If you look for parity, it's fine regardless of Mac vs PC vs whatever else used 30p SIMMs.

Your criticism might be valid versus Unix workstations, but compared to the low-end kludge together of whatever IBM didn't need at the time that was the IBM PC, the Mac was a marvel of coherent engineering. Just look at the need for things like EMS cards (the reason for this topic)... And that's me as a PC person with a distaste for Mac-style marketing saying that 😉

dionb wrote:

IIRC it varied from Mac to Mac. Take a look at the eBay listings linked to for "Mac" 16MB SIMMs above here. One's non-parity, the rest are all parity. If you look for parity, it's fine regardless of Mac vs PC vs whatever else used 30p SIMMs.

Your criticism might be valid versus Unix workstations, but compared to the low-end kludge together of whatever IBM didn't need at the time that was the IBM PC, the Mac was a marvel of coherent engineering. Just look at the need for things like EMS cards (the reason for this topic)... And that's me as a PC person with a distaste for Mac-style marketing saying that 😉

Actually back in that time, 9-chip SIMMs were much cheaper than "original" Apple branded 8-chip SIMMs.
It was widespread to buy PC SIMMs for using in Macs. In the beginning only with people who had technical knowledge or got good advice, later it became common, just to save a lot of money. And these now get sold as "Mac" memories.
Truth is that Apple saved not only at the parity, but even at the refresh counter bits. But, yes, later they changed that for a number of models, possibly to counter the data rot issues common with non-error-protected memories.