The notches on the sides are different in length, so this should be the first indication. Those with the square Motorola chips are only known to me from Apple Macs. Never saw a PC using them.

These are both designed for Pentiums and use the same 160pin EDGE connector - see https://datasheetspdf.com/pdf/1247219/Motorola/MCM72BF64/1. I actually have a Pentium motherboard with the same chips integrated.

I know which Apple modules you probably mean. But these are actually ROMs and they use a SIMM like connector. Got one in my SE/30.

mpe wrote on 2020-05-11, 11:32:

But these are actually ROMs and they use a SIMM like connector. Got one in my SE/30.

No, I don't mean the ROM modules. The ones I'm refering to were used in the early PowerMac range. I have a couple of these from some trashed 7100 and others. But you are right in that the ROM modules on these share the same connector.

Still, the notches on the two modules are different, so maybe there's some way to tell what module a mainboard is compatible with. Probably the slot compatible with the first module is higher?

I think it is just a design of that PCB rather than keying feature. It can't get any deeper as it is the key in the middle that limits how deep it can go.

I got another pipelined burst COAST with much smaller notches on sides. Still compatible.

A few years ago I also got one of those sync burst COAST modules with Motorola chips to try on a FIC PT-2003 Socket 7 board (430FX) I have that refuses to work with standard pipeline burst cache modules, it only detects cache when used with the slower async COAST module that came with the board.

So, I decided to give this sync burst module a try, and fortunately the PSU protection kicked in, preventing the PC to start so nothing was damaged. But I still don't know which machines those modules were intended for.

mpe wrote on 2020-05-11, 11:18:

I picked up a synchronous burst (flow through) COAST module (on the picture above). I was keen to run it against the standard p […]
Show full quote

I picked up a synchronous burst (flow through) COAST module (on the picture above). I was keen to run it against the standard pipelined burst stick (the one bellow) for my Pentium chipset comparison project.

DSC_7184.jpeg

I put it to a CELP slot and the only thing I got was a blue electrical smoke. Fortunately the damage is salvageable. A lesson learned.

During post-mortem I finally opened the datasheets for these modules.

Screenshot 2020-05-11 at 12.01.11.pngScreenshot 2020-05-11 at 12.01.04.png

Obviously the problem here is that the designer thought it is a good idea to put +3.3V supply where the other standard has VSS. So these are clearly not compatible.

I was wondering if there is a way of telling which motherboard was designed for which COAST or if you know about a motherboard that positively takes the synchronous burst modules. Surely no motherboard can be compatible with both given the pinout...

Wow big difference in the pinouts. Also VCC5 on pin 87 on one and pin 85 on the other... do smell smoke ? Good job finding the pin-outs !

Yep. The shorted pin in the COAST slot vanished and melted some plastic around. Surprisingly no damage to the board. Not sure about the module. Will know once I find another board to test it in 😀

well did you find a board these fit in? ^^
the datasheet doesn't seem to give much insight into what board they're actually meant for unfortunately.

I suspect I need to find a pre-Triton Pentium mb with a COAST slot. I haven't seen many of those.

One hint is that these modules don't have a TAG SRAM. That suggests they are designed for a chipset with fully integrated TAG. I mean 430LX or 430NX.

Flow-through burst synchronous SRAMs are faster than pipelined-burst SRAMs. However, they don't scale past 66 MHz and SRAMs were single sourced. That's why pipelined-burst prevailed.

Similar chips on my AST Premmia P90 board (no COAST though)

Didn't take long to find it out.

Got a new old stock spare part for DELL SP590 server. This board came with a flow-burst COAST module from the factory which seem to be similar to the other module I have.

Sadly this part has no power connector installed. I am not sure if I ever get it working in the jungle of Dell proprietary power standards. Not sure if a standard AT or ATX PSU can be adapted.

I was wondering can i use such DELL 256k module on intel ENDEVOUR mobo?