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Author Topic: Someone is selling Artix-7 Zynqs at a massive discount - legit?  (Read 4350 times)

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Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #25 on: June 24, 2017, 04:37:29 AM »
If anyone have a simple open source board layout for them it would be nice ?

It's about $500, if not more, to print a minimum amount of 6-layer ENIG boards with 4mil traces (5mil might be Ok though) and 8mil drills. This will kill all the savings from buying your chips.

You'd have to pay that much if you were using brand new chips - and as discussed earlier in the thread, unless you're breaking out literally every pin, you can get away with 4 layers just fine.

4L boards are like ~$60 for ten from most cheap board houses, I'm happy to save 50% of the cost of the full assembly if it's pretty much a one-off.
 

Offline Koen

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #26 on: June 24, 2017, 06:17:02 AM »
AllPCB have a special on leaded HASL 6-layers at 70 USD for 10 boards of 100x100.
 
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Online NorthGuy

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #27 on: June 24, 2017, 07:22:04 AM »
AllPCB have a special on leaded HASL 6-layers at 70 USD for 10 boards of 100x100.

You cannot really fan it out with 6mil wires and 12mil holes. They don't publish a separate "hole to copper" specs, but assuming it's the same as with annular ring: 12mil hole + 2*6mil annular ring + 2*6mil gaps + 6mil trace = 42mil, but the distance between ball centers is only 31 mil. So you only will be able to do the outer row of balls (perhaps the second row if you undersize ball pads). I don't think HASL would work neither.

 

Offline blueskull

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #28 on: June 24, 2017, 08:02:24 AM »
AllPCB have a special on leaded HASL 6-layers at 70 USD for 10 boards of 100x100.

You cannot really fan it out with 6mil wires and 12mil holes. They don't publish a separate "hole to copper" specs, but assuming it's the same as with annular ring: 12mil hole + 2*6mil annular ring + 2*6mil gaps + 6mil trace = 42mil, but the distance between ball centers is only 31 mil. So you only will be able to do the outer row of balls (perhaps the second row if you undersize ball pads). I don't think HASL would work neither.

If you have to save the money, I would rather choose to use a more advanced (0.2mm drill, 0.1mm track/spacing) 4-layer process rather than a standard 6-layer process.
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #29 on: June 24, 2017, 02:40:26 PM »
... I don't think HASL would work neither.

Is HASL finish significantly worse for BGA reflow?
 

Offline blueskull

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #30 on: June 24, 2017, 02:48:25 PM »
... I don't think HASL would work neither.

Is HASL finish significantly worse for BGA reflow?

For a new (less than a few weeks) board, HASL kinda works, but you need to press and nudge the chip when reflowing. Using an oven, you need very flat surface that only OSP and ENIG can give you,
SIGSEGV is inevitable if you try to talk more than you know. If I say gibberish, keep in mind that my license plate is SIGSEGV.
 

Offline eeviking

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #31 on: October 23, 2017, 11:07:02 AM »
Did anyone get boards made with these?
Any problems with solderability?

I still have some left I plan to dump for a good price in the buy/sell section.
 

Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #32 on: October 24, 2017, 12:05:33 AM »
I'm going to make a very limited breakout board for LVDS with one of the chips I bought, but not until I get the RTL working in my dev board. Might put the board into production if there's a market for it... but the 484 pin package is probably overkill.

Haven't touched the chip yet, but it doesn't look corroded or have any missing solder balls.
« Last Edit: October 24, 2017, 12:17:27 AM by cleaningOut »
 
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Offline asmi

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #33 on: October 24, 2017, 02:21:07 AM »
I've been thinking about designing a board for this SoC. Recently I found a fab that quoted me $234 for 10 6-layer boards with 0.1/0.1 mm traces and 0.2 mm drills and CI (and that price includes DHL delivery to my door), but I would like to see them deliver before I can formulate my opinion. If these parts would still be available at the time, I will definitely buy several - don't mind baking them at all.
 

Offline Tomorokoshi

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #34 on: October 24, 2017, 04:19:07 AM »
Or if you're sending hardware to the Kuiper Belt.

Now that sounds like an interesting kickstarter campaign!
 

Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #35 on: November 06, 2017, 09:25:20 PM »
It's just 0.8mm BGA, not that hard. 0.5mm is like a bitch, and 0.4mm is much harder.

For 0.8mm, you can still use dog bone fanout.

Sure, but going from 4 to 6 layers quadruples the price of the PCB. Any fabs you recommend?

I don't know if Zynq requires 32-bit DDRIII, but I've done 16-bit DDRIII for iMX6ULL, and that's doable with 4-layer, 0.2mm drill and 0.1mm track process without any advanced tech such as blind/buried vias, HDI and so on.
Top: trace
M1: GND/PWR
M2: GND
Bot: trace
It can do 8-, 16-, 18- and 32-bit DDR3. (18-bit DDR3 is 16-bit DDR3 with ECC.)

I'm having a strange issue with the schematic for wiring up an 8-bit DDR3 to this chip, since I want to stay at 4 layers. The 512x8 DDR3 chip has 16 address bits [15:0], but the 256x16 DDR3s have only 15 [14:0], and apparently the Zynq bank 502 doesn't have a 16th address bit either. I can't find any documentation on what to do with the DDR's A15 pin - any suggestions?

Options are to let it float or tie to 1V5/ground.
« Last Edit: November 06, 2017, 09:34:07 PM by cleaningOut »
 

Offline asmi

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #36 on: November 07, 2017, 01:17:29 AM »
I'm having a strange issue with the schematic for wiring up an 8-bit DDR3 to this chip, since I want to stay at 4 layers. The 512x8 DDR3 chip has 16 address bits [15:0], but the 256x16 DDR3s have only 15 [14:0], and apparently the Zynq bank 502 doesn't have a 16th address bit either. I can't find any documentation on what to do with the DDR's A15 pin - any suggestions?

Options are to let it float or tie to 1V5/ground.
If you don't want to use smaller density ICs with 15 address lines (I personally would've chosen that option), you can tie unused address line high or low (it doesn't really matter either way), but don't let it float! Keep in mind that different density ICs have different refresh times, so make sure you specify correct parameters when setting up DDR3 controller.

Also - I would love to see how you managed to breakout DDR3 lines using only 2 layers (as other two will need to be reference planes to maintain signal integrity). DDR3 traces NEED to have UNBROKEN reference plane along their entire length. This is even more so if you want to use DDR3L as it has even smaller margin than regular DDR3. Even with 0.1 mm traces and 0.2 mm drills process that would not be easy as Zynq is in 0.8mm pitch BGA package so you can't fit two traces between balls/vias.
« Last Edit: November 07, 2017, 03:09:38 AM by asmi »
 
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Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #37 on: November 07, 2017, 03:04:43 AM »
 :palm:

I should have realized the lack of a 16th address bit means I can only access half of the actual depth (0-256 of 512M), so there's no benefit to using the DDR3-x8 ICs. I considered using DDR3L, but minimizing voltage bus count feels more useful than reducing cost/power. On this board, at least.

I'm not even at the stage where I can work on the layout yet - still have to get an Ethernet PHY into the schematic. I may record the layout towards the end of this week if anyone's interested.
« Last Edit: November 07, 2017, 12:34:26 PM by cleaningOut »
 

Offline asmi

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #38 on: November 07, 2017, 03:20:38 AM »
I should have realized the lack of a 16th address bit means I can only access half of the actual depth (0-256 of 512M), so there's no benefit to using the DDR3-x8 ICs. I considered using DDR3L, but minimizing voltage bus count feels more useful than reducing cost/power. On this board, at least.
Make sure your 1.5 V rail can provide enough current - DDR3 can have huge transient currents (in the order of few Amps!), and if you PMIC (or power source) isn't quite up to task, you could get hard-to-debug issues caused by 1V5 rail going places. Also Xilinx recommends using termination to Vtt, so you will need tracking regulator for that. Read Ch.5 of UG933 very carefully and do as they say. Unless you are willing to experiment (read - got money to burn on possible board respins) that is.

I'm not even at the stage where I can work on the layout yet - still have to get an Ethernet PHY into the schematic. I may livestream the layout towards the end of this week if anyone's interested.
I doubt I can make it on the livestream (as my spare time is always sketchy), but would love to watch full-length recording at my own schedule. Don't mind 5+ hrs long YT videos at all.
But like I said, I seriously doubt you would be able to make it work on 4 layers. It least I couldn't make even much simpler Artix-7 + DDR3L x8 work on 4 layers without violating DDR3 layout requirements.
My first 6-layer boards are now on their way to me - looking forward to get my hands on them :D
« Last Edit: November 07, 2017, 03:26:52 AM by asmi »
 

Offline ThomasDK

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #39 on: November 07, 2017, 08:12:35 AM »
I'm having a strange issue with the schematic for wiring up an 8-bit DDR3 to this chip, since I want to stay at 4 layers. The 512x8 DDR3 chip has 16 address bits [15:0], but the 256x16 DDR3s have only 15 [14:0], and apparently the Zynq bank 502 doesn't have a 16th address bit either. I can't find any documentation on what to do with the DDR's A15 pin - any suggestions?

Options are to let it float or tie to 1V5/ground.
The Zynq PS only supports 16 and 32 bit databus, so you need at least 16 bits.

The address bus is behind the data lines, stretching all the way in to the 7th row  :scared:  (see attached)

I doubt it can be fanned out in 4 layers, I would go for 6. This would also allow a 32 bit databus, doubling the memory bandwidth  :box:.

Thomas
 

Offline cleaningOut

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #40 on: November 07, 2017, 09:07:55 AM »
I'm having a strange issue with the schematic for wiring up an 8-bit DDR3 to this chip, since I want to stay at 4 layers. The 512x8 DDR3 chip has 16 address bits [15:0], but the 256x16 DDR3s have only 15 [14:0], and apparently the Zynq bank 502 doesn't have a 16th address bit either. I can't find any documentation on what to do with the DDR's A15 pin - any suggestions?

Options are to let it float or tie to 1V5/ground.
The Zynq PS only supports 16 and 32 bit databus, so you need at least 16 bits.

The address bus is behind the data lines, stretching all the way in to the 7th row  :scared:  (see attached)

I doubt it can be fanned out in 4 layers, I would go for 6. This would also allow a 32 bit databus, doubling the memory bandwidth  :box:.

Thomas

The TRM states (section 10.1.15) that the PS supports from 8- to -32 on all Artix-7 devices except the z7007s and z7010. Did you find a different source somewhere, or am I reading it incorrectly?
 

Offline Someone

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #41 on: November 07, 2017, 09:39:43 AM »
I'm having a strange issue with the schematic for wiring up an 8-bit DDR3 to this chip, since I want to stay at 4 layers. The 512x8 DDR3 chip has 16 address bits [15:0], but the 256x16 DDR3s have only 15 [14:0], and apparently the Zynq bank 502 doesn't have a 16th address bit either. I can't find any documentation on what to do with the DDR's A15 pin - any suggestions?

Options are to let it float or tie to 1V5/ground.
The Zynq PS only supports 16 and 32 bit databus, so you need at least 16 bits.

The address bus is behind the data lines, stretching all the way in to the 7th row  :scared:  (see attached)

I doubt it can be fanned out in 4 layers, I would go for 6. This would also allow a 32 bit databus, doubling the memory bandwidth  :box:.

Thomas

The TRM states (section 10.1.15) that the PS supports from 8- to -32 on all Artix-7 devices except the z7007s and z7010. Did you find a different source somewhere, or am I reading it incorrectly?
Components of minimum x8, for a total bus width of 16 or 32 bits.
 
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Offline ThomasDK

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #42 on: November 07, 2017, 09:49:43 AM »
The TRM states (section 10.1.15) that the PS supports from 8- to -32 on all Artix-7 devices except the z7007s and z7010. Did you find a different source somewhere, or am I reading it incorrectly?

https://www.xilinx.com/support/documentation/sw_manuals/xilinx14_1/platform_studio/ps_r_gui_zynq_tab.htm

Quote
Note 8 bit interfaces are not supported; however, 8-bit parts can be used to create 16/32-bit interfaces.
 
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Offline eeviking

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #43 on: November 08, 2017, 03:08:24 AM »
I also have a bunch of DDR3L MT41K128M16JT-125 IT:K FBGA's if anyone is interested :D
Will they work with the Zynq?
 

Offline asmi

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Re: Someone is selling Artix-7 Zynqs at a massive discount - legit?
« Reply #44 on: November 08, 2017, 05:43:49 AM »
I also have a bunch of DDR3L MT41K128M16JT-125 IT:K FBGA's if anyone is interested :D
Will they work with the Zynq?
I've just ordered some of those exact modules from Arrow, as I couldn't find them anywhere else.
I don't see any reason why they won't work with Zynq.
 


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