pshipkov wrote on 2022-12-18, 08:32:

Good chance some of the settings are slightly off without clear indication what exactly.
The tools in that page can easily do that.

Don't think so. I leave the page, click back on JLCPCB promo start page, then click back on my cart, and the value is now at $2.50. Brilliant.

Maybe click the standard precision tab?

Anyway, I've ordered 5 pcs. The price gets absurd again for 10+. I've plenty extra alpha1 pieces. The cost difference, at the time, between 5 pcs and 20 pcs was $10.

I suspect JLCPCB is loosing money on this promotion. It is entirely for marketing.

Since I plan on installing this in this mobo it seems appropriate to document here

I fired it up today for a base benchmark. Here are my results:

Amd 386 dx 40mhz is what is soldered on the board.

Excited to see how the sxl2 improves things :p

Sphere, I wonder if there could be some benefit in making the SXL2 interposer as 8-layer while the $2 JLCPCB deal is still on. You could add two GND layers between the data layers. Would this take much effort?

For this size PCB, normally
6-layer is $60, sale is $2
8-layer is $86, sale is $2
10-layer is $187
12-layer is $257

So for another $2, we could see if adding those ground planes help in any way, and if not it was $2.

The ground layer is pretty solid now. I think we have a winner as is. But a full ground layer between all layers would require 11 layers which isn’t a standard stackup. And a new top layer would be a lot of work.

Na, it’s good as is.

Those rotator boards on the other hand…… o _O

If you want I could make a stackup like this though pretty easily. 12 layer

Red
Ground
Signal
Ground
Signal
Ground
Ground
Signal
Ground
Signal
Ground
Blue

This will put the layers and signal closer to other copper on the 1.6mm pcb

Na, I think leave it as is. Like I said the ground plane is pretty good on latest version after adding those vias.

The thought concerning adding two ground planes was more for shielding one or two of the data planes, not so much for increasing robustness of the general ground plane.

There is substantial impedance difference between 'mostly ground with some signals' vs actual uninterrupted ground. On the other hand it all ends up at the actual motherboard where we find ourselves in an ultra pure copper power wires wound by monk virgins from Great St. Bernard monastery plugged into 40 year old power socket situation https://parttimeaudiophile.com/2022/06/05/the … de-summer-2022/

Point that may not have gotten understood is if we add two more layers. All layers get closer. So we help some and hurt others. The pcb will still only be 1.6mm thick

Unless 12 layer is on the table. We should leave as is.

I see. I don't know how this can be calculated theoretically. I'm sure there's some simulation programs to determine it. I checked JLCPCB for 8-layer and 2.0 mm thick, but the $2 price went to $143.

Btw, here is an example of how the silk is clearanced after gerber generation.

This showed as pads covered on 3d view prior to mfg.

Unfortunately jlcpcb did not manufacture the D pad shape that I created it seems. Or at least they did a very poor job approximating it

These are the same settings and pads I used on this sxl2 interposer so this is the result you can expect. Doesn’t seem like there is much we can do about it, I mean we could ask them, but it isn’t important. This will work.

But I’ll be removing the D shape so that the surrounding copper will pull in since it ends up round anyway… 🤣

Sphere478 wrote on 2023-01-01, 00:17:

Unfortunately jlcpcb did not manufacture the D pad shape that I created it seems. Or at least they did a very poor job approximating it

they didnt look like proper pads to begin with. You put multiple features on top of each other, most likely someone suspected its a glitch and manually fixed them out of the design 😀
imo "chamfered with other corners rounded" was the proper way to go Re: Custom interposer module for TI486SXL2-66 PGA168 to PGA132 - HELP!

Pull them up in gerber view. This is what jlc was sent.

They don’t mess with the kicad files at all, just the gerber files. And I don’t think they are all that easy to edit. It may be that the process of manufacturing vias and plated thru holes uses some kind of process that doesn’t allow this shape?

These are pics from the gerbers of the latest version ulpoaded here. I used those same pads on the other project.

Edit: those looking for the last version that I uploaded as of july 17 2023 this is it.

Latest version as of this post

Updated order files for round pads. (corrects flood around pads since pads come in round anyway.)

I received the new PCBs today, which arrived on a Sunday. This is odd, so perhaps some independent carrier did the delivery. Or maybe Canada Post is still trying to deplete the Christmas pileup.

I need to work on some other things, namely this Anyone own an Asus PCI/I-P54TP4 with pipeline burst SRAM? Planning to mod direct-mapped SRAM to pipelineburst and this Anyone here able to modify a Lenovo laptop T61 BIOS? before I will be able to continue testing on the SXL2 prototype.

Yay!

When you have time. Some high res scans would be cool 😀

My mobo is ready to for some sxl2 overclocking!

Just got the AnyClk device installed! Pretty nifty little device! First test was at 40mhz on a AMD 386dx-40 (soldered on one) next was at 50mhz cpu /100mhz crystal clock. So far stable! More mhz to come!

Edit: tried 5.33x multi. No dice. (106.7fsb) so my max mhz on this cpu lies somewhere between 100 and 106.7 crystal clock.

I have the crystals to find out exactly where, in steps that are actually often less than 1mhz at a time. 😮

So when I get the sxl2 I’m really gonna know what its max clock is for sure 🤣.

I haven’t messed with isa clock ratio. Might try that next. Could be the limiting factor. Also I have some purple ram coming 4mb x 8 (32mb) so this system should be flying soon! :p pic doesn’t show it, but I ordered parity ram.

Hi,

Has anybody tested this interposer on an Inboard/386? If I read correctly this allows a 486 sxl2 to be used in a regular 386DX socket - is that correct? Is so, how does one get their hands on one?

Thanks,

Chris

chjmartin2 wrote on 2023-01-11, 14:25:

Hi, […]
Show full quote

Hi,

Has anybody tested this interposer on an Inboard/386? If I read correctly this allows a 486 sxl2 to be used in a regular 386DX socket - is that correct? Is so, how does one get their hands on one?

Thanks,

Chris

Do you mean using it on a soldered on cpu board? That has no socket?

We have been using it on boards with pga 132 sockets

It might be possible to put it on boards with solder pads only.

Feiopa, any thoughts on what hardware we could use for that?

Likewise I’m interested in this for both use on an Intel inboard/386 and an ibm p70

The inboard was an accelerator card made by Intel to upgrade the cpu and ram for an 8088 machine, mine came in an IBM 5150

See below: https://wiki.preterhuman.net/Intel_Inboard_386/PC

They are pretty rare in the wild but a few of us have these unicorns..

There are also daughterboards for these cards to increase the ram and there’s already a modern project to replicate this ram upgrade (also building one when the parts arrive)

I’m eager to get my hands on an interposer of this type when it’s ready..

Mike