ATX PSU conversion

[Doobrey]

redrumloa wrote:
I'd personally recomend verifying voltages with a multimeter.

I`d second that.. never ever go by cable colour alone...unless you can afford to replace your Amiga!
 The ATX spec recommends cable colour, but it`s just that...a recommendation.

 I just spent an exciting evening trying to get my spare A1200 working.. nothing but a black screen.I pushed and wiggled everything in sight, still no change..
 After the usual caffeine fix to reboot the brain, I dug out my multimeter and checked the PSU (standard beige CBM brick)... 3v on both the +12 and +5v rails !!
 Luckily I`d just got a MicroATX PSU..just needed a strip of terminal connectors and a toggle switch and I was back up and running in no time !

[Wolfe]

Doobrey

Excellent quick fix.  Are you going to put it inside your A1200?   :-D

[Doobrey]

@Wolfe..
Well, to put it inside would mean there would have to be a case of some description !
 At the moment, it`s the A1200 mobo, Z4 busboard, Apollo 040, PCMCIA network card, silversurfer and a Hypercom3 just sitting on the bottom half of the A1200 case ..with wires running everywhere... :-o

 I`ll have to take some pics of it later..looks like a mad scientists lab here !

[amigean]

My current project is on my desktop A1200 with internal cdrw which limits my internal space more than normal. I have some cardboard cut outs of the PSU's taken from some mates. I am doing some plastic remolding work to add an additional inch to the upper A1200 case. If I am successful I will be able to keep the internal floppy drive and will use the Audio Forge PW120, but if I loose the floppy then I will use the smaller square PW120a. Either way I'm having fun. Plus I am repainting the keyboard and will also paint the case something other than beige!

Sounds great Wolfe!!! I would like to do something similar myself - could you possibly post some pics of your 'altered' A1200? I would be very interested....

I think it's a cool idea
 ;-)

[Wolfe]

@Doobrey

Dr. FrankenAmigaStien I pressume?   :lol:

Sounds like you are going to need more than a standard A1200 case. Planning to use Zorro board or did you get it just for the extra Clock Ports?

[Wolfe]

@amigean

Currently mine is in pieces. but this link has pictures of one similar enough to mine to give you a look 'n see.

  A1200CD

I decided to paint the keyboard and the case.  Tired of beige.
Then the power supply died   :-o  (homemade PC power unit) so i decided I would try to fit a powerboard inside and am currently in the middle of a plastic molding experiment to increase the vented top area of the desktop A1200 top case back roughly an inch and a quarter.  I want to keep my internal floppy.  But when I am finished  I will definetly post pics.

When looking at the URL above you will notice the only way to fit a cdrom completely inside is to have it cut into the bottom case as well.  

When done (if successful) the cdrw will be mounted on the inside of the upper case only which will also give more vents and space for the powerboard and "Still" keep its portability and similarity of design to the original case.  :-D

[Doobrey]

Wolfe wrote:
@Doobrey
Planning to use Zorro board or did you get it just for the extra Clock Ports?

 Well, I saw the Z4 on ebay and got it for £7 !
The seller said he couldn`t get it to work with his accelerator so it was sold for spares, but after some jumper swapping I`ve got it going fine ( Sorry if the seller is reading this!)
 If a decent (ie cheap) X-Surf or Ariadne II come up for sale, then I can ditch the PCMCIA netcard, as they`re too slow and CPU intensive.

 Anyway, I got it just to play around with...the extra clockports do give me some ideas...

 

[mantisspider]

£7 ? now thats one of the best bargains ive seen so far

[patrik]

@Doobrey:

Dont take for granted that the ZorroII network-card will be much less cpu intensive and faster than the PCMCIA one. Both types often work in kind of the same way - not using DMA-transfers when moving data between the buffers of the network-card and Amiga-memory and instead utilizing the CPU for that task. The card which has the lowest access-time will though waste the least amount of CPU-cycles as waitstates and thus hog the CPU for the least amount of time. That will though vary from card to card and bus to bus.

I do think there were a card made by GVP which utilized DMA-transfers between buffer and Amiga-memory but I am not sure.

Keep in mind that shuffling data over a network using TCP/IP is quite CPU intensive in its nature because of the quite large amount of datashuffling and calculations required to get the data through all layers from the hardware to the application.

Using a network-card which transfers its buffers using DMA to/from Amiga-memory would reduce the CPU-usage in one link between two layers to a minimum, but as the data still has to go through the layers of the TCP/IP-stack it wont have an earthshattering effect on CPU-usage... still I wouldnt mind having a network card with this ability . Then consider the difference when using network applications between two network-cards not using DMA... It will most likely be neglectible (assuming the device-drivers for both cards are written in a sensible matter).

My point anyhow is that as ZorroII network cards usually are quite expensive, this card switch you are planning might cost you alot more than it tastes... it is not even for sure it tastes any better, could taste worse .

Take care!


/Patrik

[patrik]

@Wolfe:

That was definately one neat modification to the A1200. Be sure to post some pictures of your construction as soon as possible .


/Patrik

[mantisspider]

my cables came from montek
:-D they estimated up to 6 weeks but i got them in less than 2.

[Doobrey]

@Patrik,
 I`ve got an A4000 040 with AriadneII, and an A1200 040 with a CN40BC (PCMCIA) card.
 A4000 gets around 750-800 kb/s over the network, whilst the A1200 gets 200-300kb/s and Workbench gets very unresponsive ,while it`s fine on the A4000

[patrik]

@Doobrey:

What TCP/IP stacks are you using on those configurations? AmiTCP atleast doubles the results when using the cnet.device compared to Miami as Miami needs a MNI-driver for a card to give good performance.

I have had no problems of reaching 700KB/Sec with the CNET card using AmiTCP, still maintaining a very responsible computer. Though that is with a ftp client which isnt a very good performance measure, a http transfer ala 'wget' would be much better measure as http transfers eats MUCH less cpu cycles than a ftp transfer.

Also, check your switch/hub if the CNET card is rendering many collisions when transferring data. Atleast my card seems to be of very low quality and works very bad with certain switches/hubs and renders lots of collissions with those. A lot of collissions will generate a lot of interrupts which would burden the cpu quite some more than when doing transfers without collissions.


/Patrik

[cycloid]

surely if one were removing the floppy drive to make space you'd stick the CD drive there.... e.g. my "1250"
 http://amiga.org/gallery/photo.php?lid=995

it seems a bit od sticking it on the left.

however, on the subject of power supplies: does anyone know what -12v is actually for? as asked earlier in the thread. as i have some small psus out of a big fat server setup that only deliver 12 and 5v. they originally powered two large scisi drives each (and i mean LARGE, the pair would be equivilent in mass to a car baterry!) and i reckon i could squeeze it into my aforementioned 500 case mod. but alas no 12v. unless, of course, i could use an inverter to deliver the -12v, but that depends on the rating etc.

[Doobrey]

cycloid wrote:
however, on the subject of power supplies: does anyone know what -12v is actually for

Serial port and  audio need -12v.

[Doobrey]

patrik wrote:
@Doobrey:

What TCP/IP stacks are you using on those configurations?

 Genesis on both machines.. the wierd thing is that the AriadneII seems to generate more collisions than the Cnet, and then only when sending..receiving is fine.