sloatload iMac MLBs interchangable?

15 replies [Last post]
dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900

I'd like to upgrade my daughter's 400MHz iMac to a later MLB with a 500/600/700 CPU and 16MB VRAM. The 600/700 MLBs sell for a premium but 500s can be had pretty cheap.

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.
dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
so . . .

My question is: how can I be sure a 500MHz MLB is from the last serie with 16MB VRAM? I've perused lowendmac's iMac chart and if it's accurate I figure I might be able to suss out what I need to know from eBay auction details. If you look to the righthand side of the chart, you'll see I want a North American 500MHz or better Early 2001 or Summer 2001 MLB with the 16MB VRAM ATI RAGE Ultra 128 GPU.

Many auctions for 600/700MHz MLBs list a part number 820-1275-A, which isn't a 'real' Apple PN of course, but most likely the MLB PCB's number. A number of auctions for 500MHz MLBs have included that 'part number', is that the clue I need to ensure I'm buying a 16MB VRAM MLB?

Oh, and finally, I'm assuming any SL iMac MLB can be used in any SL iMac. Can anyone offer confirmation (or otherwise) on that?

Oh, and finally finally (heh heh), I've also assumed that (besides the faster CPU clock) a Rage Ultra 128 will be a more capable and faster GPU than the 128 VR GPU her imac currently has. I'd like her to be able to play some of the lower-end 3D games (Harry Potter 1 & 2 come to mind), which right now are a bit jerky and pokey. Also, I'm hoping VLC playback of .mp4-encoded flicks will be smoother, now on her 400 they are rather less than smooth-playing.

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

cwsmith's picture
Offline
Joined: Oct 13 2005
Posts: 699
My Blueberry iMac (slotloadin

My Blueberry iMac (slotloading) came from the factory with a 350 MHz MLB. It was dead.

I took the 500 MHz MLB from a Graphite iMac DV and swapped it in. Success!

I would say the upgrade you're proposing should work just fine.

HOWEVER, ...

There's a very good chance you'll need to update the firmware on the new MLB so it can boot to OS X. I strongly recommend you boot the machine to OS 9, then download and run the firmware update (up to but not including the restart), BEFORE you try to boot the new MLB into OS X.

Without the firmware update, you will have no video, and although you can do the update after the fact, it's a lot tougher to to! If it turns out you didn't need to update, the machine will tell you so and it's no big deal. If you should have, but you didn't, oy vey.

__________________

Dozens of Macs; a handful of PCs; Apple ][e, ][c and ][gs; a few iPods; lots of parts
17 guitars, 2 baritone guitars, alto guitar, 6 bass guitars, bajo sexto, 3 ukuleles, mandolin, banjo, sitar
3/4 scale upright bass, 4pc drum kit, congas, travel congas, bongos, cajon, cabasa, 12 harmonicas
http://www.cwsmith.fmhttp://www.facebook.com/cwsmith2620

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
notes on MLBs

OK, from the depths of my basement shop, I dug out a couple of 400MHz MLBs and noted the 'part numbers', neither of which were the 820-1275 number I think I want:

MLB #1 - 820-1051-A - 400MHz 64MB c1999 - this is probably the same as our 400MHz Blueberry iMac's MLB, an original series SL 400 DV

MLB #2 - 820-1131-A - 400MHz 64MB c2000 - probably from an Indigo or Ruby Summer 2000, it should have a Rage Pro 128 GPU.

These are noticably different parts, at least the PCB layout differs a bit between them, though the CPUs are identically located.

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
re: Graphite iMac DV

Thanks cw!

Quote:

I took the 500 MHz MLB from a Graphite iMac DV and swapped it in. Success!

That's also a Summer 2000 MLB, so now at least I'm reassured that series should swap OK. now the later models . . . ?

Great point on the firmware update, that's the kind of thing I'm sure I'd forget. You know, just slap in a new MLB, fire it back up into OS X and - Boom! Crying

dan

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

Jon's picture
Jon
Offline
Joined: Dec 20 2003
Posts: 2804
One thing I remember seeing i

One thing I remember seeing is that the position of the heatsink block may differ on the later/faster mobos.

__________________

I am not in this world to live up to other people's expectations, nor do I feel that the world must live up to mine. - Fritz Perls

davintosh's picture
Offline
Joined: Dec 20 2003
Posts: 554
Re: One thing I remember seeing i

Jon wrote:

One thing I remember seeing is that the position of the heatsink block may differ on the later/faster mobos.

I can confirm that; see this thread.

To answer the original question, yes, they are interchangeable, but you've got to watch the heatsink, especially with the faster units.

__________________

Obsolescence is just a lack of imagination.
Visit my blog: davintosh.com -- it may not be up to date, and it may not be exciting, but you can say you've been there.

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
alrighty then!

Thanks to the very generous MaxTek I now have a 600MHz iMac MLB running in my daughter's SL DV iMac. It was a pretty simple swap, needing only a slight amount of fabrication. It feels noticably faster and a couple of simple benchmarks confirm that impression.

As noted, the CPU heatsink is located in another place on the later MLBs. The SL DV has a screwed-down heatsink block which, in addition to being in the wrong place, is slightly too thin. I unscrewed the block, determined its correct location, and figured I needed about a mm of extra thickness. I dug out a scrap of AL sheet about that thick and cut a little square to size. I ensured the shim was flat by sanding it on a sheet of wet/dry paper, then inserted it between the divider plate and the heatsink block with some heatsink goop between the layers. Then I used some thin cable ties to hold the block/shim combo in place.

Laughing out loud I actually remembered to boot into OS9 first to check the firmware version, which fortunately was up-to-date.

Testing reveals (as expected) a faster system. On the 400MHz MLB I ran a MacQuake timedemo under OS9 at max settings @ 640x and 800x, got 22FPS and 14FPS respectively. With the 600MHz MLB, I got 32FPS and 22FPS.

On the 600 I also reran some .mp4 video rips that previously were slightly jerky which now run perfectly smoothly.

No other issues, everything else worked perfectly. I did have an extended 'scare' when the ethernet didn't bring up a valid connection with my router. After messing with the iMac for an hour or so I finally discoverd my &^$&(^%^^ router had crashed. Duh. Enet worked fine once router was restarted. Whenever I use bittorrent (from other Macs on my LAN), all those connections seem to overwhelm my old D-Link router.

Thanks again to all, esp MaxTek for the great deal on the 600MHz MLB.

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
only weirdness so far . . .

is the 'pilot light' behind the power button glows only orange, never green. Oh, and the power key on the keyboard won't start it no mo', only can startup from that orange-only front power button.

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

Jon's picture
Jon
Offline
Joined: Dec 20 2003
Posts: 2804
IIRC, the keyboard PB stopped

IIRC, the keyboard PB stopped working at 400 DVs and up. I think it works on the 350s I've got, but not the 400 DV mobo.

__________________

I am not in this world to live up to other people's expectations, nor do I feel that the world must live up to mine. - Fritz Perls

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
keyboard power button . . .

worked on our iMac with the 400MHz MLB, now doesn't work with 600MHz MLB. FYI. Tongue

dan k

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net

olikicksmacs's picture
Offline
Joined: Dec 20 2003
Posts: 252
Voltages?

If i bought a US imac logic board, and put it in a UK imac, would the voltage change make a difference or would the board fry?

Thanks

__________________

iMac Tangerine G3 600mhz (Gary), Dell Inspiron 6000 (Delila)

cwsmith's picture
Offline
Joined: Oct 13 2005
Posts: 699
Auto-detect.

Voltage & AC frequency should auto-detect. I can bring any Apple computer (from the ][ series to present) from the US to the UK, purchase the correct wall cord, plug it in, and get right to work.

__________________

Dozens of Macs; a handful of PCs; Apple ][e, ][c and ][gs; a few iPods; lots of parts
17 guitars, 2 baritone guitars, alto guitar, 6 bass guitars, bajo sexto, 3 ukuleles, mandolin, banjo, sitar
3/4 scale upright bass, 4pc drum kit, congas, travel congas, bongos, cajon, cabasa, 12 harmonicas
http://www.cwsmith.fmhttp://www.facebook.com/cwsmith2620

DrBunsen's picture
Offline
Joined: Dec 20 2003
Posts: 946
The power supply is the part

The power supply is the part that interfaces to the outside world's power, not the logic board. The logic boards are standard, only the power supply needs to be correct, and they are auto detecting.

__________________

Damn the Torx screws, full speed ahead!
Apple and Wireless FAQ

Offline
Joined: Dec 20 2003
Posts: 851
There are two different mothe

There are two different motherboards that were used in that series. One used the 750 Ceramic G3 CPU and Uni-N, and the other one used the shiny metal 750fx or 750gx CPU with Pangea. These two boards are identical in every other way. However, they are not interchangeable because the CPU's are in slightly different locations, and different thicknesses and will not interface with the heatsink properly.

Your 400 is the Ceramic G3 cpu version, so you'll need to find another one of those.

__________________

Dr. Bob
Applefritter Admin

dankephoto's picture
Offline
Joined: Dec 20 2003
Posts: 1900
identifying 16MB VRAM iMac MLBs

The boards with the silver heatsink in the center of the bottom side (the side with the RAM slots) are the later 16MB VRAM MLBs.

Also, if its a 16MB VRAM model, the barcode label should include one of these two codes "P52" or "P66" alongside the CPU speed.

Also, the "820-1275-A" PCB number does seem to be one you'd want, it appears to be common to the series (whatever the CPU speed.)

Keep in mind of course, when upgrading you still may need to move the heatsink when the CPUs are in different locations. Reading drbob's note above, that may mean grabbing the big separator plate from the donor iMac. On the 16MB VRAM models the heatsink is a stamped bit of that part and NOT movable (where on the older models it is.)

----------------------------------

Sorry to resurrect this thread from the long dead, but I wanted to add this info I dug up in response to a recent private query. Hopefully this will help folks looking for a suitable MLB with which to do this upgrade.

dan k

PS: would any mod care to change the thread title to slotload from "sloatload" for me and then snip out this "PS"? much obliged!

__________________

|| web page gone - curse you Comcast! | Applish goodies servers offline, sorry! |
» email macdan at comcast.net