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Bolle

Carrera040 cachecard add-on cloning

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The topic of cloning the cache card for the Carrera040 came up in another thread so I would like to gather some information here to push this forward.

First off: can someone tell me what kind of connector they used and if I can get one (or an equivalent) somewhere?

 

povd460.jpg

 

exvBsoz.jpg

 

2Rc4kXc.jpg

 

We're looking for something with 1.27mm of pitch and 2 rows of 50 pins.

Preferably should match the original pad spacing so I can keep the original layout:

 

662548353_Bildschirmfoto2020-04-14um16_08_02.thumb.png.89e591bb39eb53755c859310b58e41fa.png

 

 

Schematics so far:

CarreraCache.thumb.png.61f0519999791ca3f7574a5c5a73532b.png

 

Working on finishing the board routing and getting the GALs cracked right now.

Edited by Bolle

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Yeah, same connector on some versions of the ATi Mach64 for the VRAM expansion cards it seems:
image.png.57d6068151b2ac6c8814b89c61b763b7.png

 

Looks like mdeverhart is on the right track there.

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They definitely don't look like they would be easy to source, I hope I'm proven wrong. 

 

If you do score a load, how do you hope to solder them on? Looks like it would be a real bugger to do by hand.

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Going to have to see if I can fit through hole mounted connectors in place. The original (and the PCB I routed so far) uses a SMD connector.

I will have to check if there is enough space.

 

Also I advanced on the GAL front. Was able to read out something from all three of them but two fusemaps won’t disassemble into equations using opaljr. The one that does convert into equations looks fine.

Didn’t have time today to burn the extracted fusemaps onto new chips yet.

I will do that tomorrow to verify if the fusemaps are valid.

Edited by Bolle

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GAL copies confirmed:

 

MlyOa7l.jpg

 

Jedec files, equations and schematics attached. I'll order a set of test boards once I finish something else that I am working on to save shipping costs.

If someone wants to make themselves a board in the meantime let me know and I'll send gerber files along.

 

cflFF9A.png

 

 

 

U1_1.jed.jed

U1.EQN

U2_syn_ac_correct.jed

U2.EQN

U3_syn_ac_correct.jed

U3.EQN

Cachecard.sch

Edited by Bolle

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I have a set of 5 prototype boards on the way together with some other exciting stuff.

Once the boards are confirmed to work I will share the gerber files (and pass on the remaining 4 proto boards that I don't need - in case they do work)

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Looking good...

 

IMG_3516.thumb.jpg.0bd3831671724299f9f43af28f6b50f5.jpg

 

IMG_3539.thumb.jpg.ca3dc1226611b003ce0196aabd8e9c3c.jpg

 

On one of my Carreras the cloned cache card would not be stable with 40MHz. Everything is fine at 33MHz though.

After some back and forth it turned out that not all combinations of CPU and cachecard will run at 40MHz.

I swapped around different CPUs and even found a combination where the original cachecard would refuse to work resulting in a hard crash once the Carrera INIT loads.

 

I will be revising the PCB design a little and then post the gerbers and a BOM so everyone can build their own cachecards.

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Gerbers attached.

 

BOM

 

-C1-C11: 0.1uF 1206 ceramic caps

-C12, C13: 22uF/10V tantalum or electrolyte caps

-R1: 330Ohm 

-R2, R3: 220Ohm

->pad size is metric 1206 for all the above resistors and caps

 

-U5-U8: 32K x 8 SRAM 15ns SOJ (IS61C256AL-15JL, IDT71256SA15 and the like)

-U9, U10: 8K x 8 TAG SRAM 12ns SOJ (ATT7C174J-12, IDT71D74S12... only exists as NOS, no modern replacement)

-U1: GAL20V8 10ns (7ns works as well) PLCC28

-U2, U3: GAL20V8 7ns PLCC28

-U11: 74F74 SO14

-U12: 74F125 SO14

 

-J1: 1.27mm pitch 2 x 50 SMD pin headers

 

cachecard.zip

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Oh this is looking fantastic!

 

Hats off to you sir, I have no idea how you pulled this off but you have.

 

Will be following closely and hopefully will take one of these for my Cache-less one in my IIci if you ever sell one. 

 

Pretty sure mine's a 40MHz one so not sure if I will have some stability issues my end. Might be worth compiling a list of tested CPU's.

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On 7/2/2020 at 11:55 PM, Unknown_K said:

How many people actually own a Carrerra? I have one with cache if my memory is correct.

I have one. I think it’s in one of my IIci or se/30s. Pretty sure it didn’t come with a cache card. 

Edited by TimHD

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