Possible new cheapmod for original Xbox?

Well,I came across the Cheapmod for Xbox (the original one,way before Llama's PCB chepamod)and it stated only SST49LF020 chips will work.
Now,I was out of luck because all of my chips were either 4MB (512K)or were 49LF002A chips,and 2 PMC chips ,one 256KB and one twice the size (512kb).

What I thought?Why not try and remake it to work with PMC chips? (SST chips I have were missing some signals)

And so I started searching for datasheets,and a pinout of the Xbox' LPC port.
All good and nice,I've found datasheets for the 2 PMC chips (in fact,PMC-Sierra used the same pinout for both chips ^_^),made a diagram using Paint and noticed that I was missing 5v.

My question is,do I REALLY REALLY REALLY need 5v? The PMC chips are rated for 3.0 - 3.6V operation range.

Here's the diagram I made. If needed I can make a better one. I color coded the pins to make it easier to know which wire goes where.

 

hello, the SST49LF020 chip was a special chip. the SST49LF020A chip or any other chip does not work for cheapmode. i will search the net and come with the proof to back this up.

edit: something to do with diferent adressing of the chip memory

 

I researched quite some time on the subject for my new modchip.

Here it is. Cheapmods will only work with a SST49LF020 because there is a design bug that makes the flash chip ignores address bits higher than A17 when the Xbox drives the flash chip. This bug was corrected in the SST49LF020A and all other LPC flash chips from SST.

The Xbox needs to load a 1MB image file at the top of it's address space and so the SST49LF020 which is 256KB will simply read the same BIOS image 4 times in a loop even if A19 and A18 are toggled for the 3 last 256KB chunks.

For your other question, 3.3V is the only source of power you'd need. To be blunt, this will not work. The SST49LF020 was the only chip that could work without additional logic (CPLD). Moreover, just for the sake of the exercice, you'd have to ground ID0-ID4 and LPC-Parallel bits in your design.

Better use a Aladdin XT which will also work on Xbox revsion higher than 1.1.

 

Well,then will it work if I use the FLASHROM method (soldering it underside,see pic for v1.4 below) but instead of using a flashrom to use a PLCC chip? The FLASHROM is in DIP32 package which means it has 32 pins,and so has the PLCC chip.
Also I have a 49LF040.I assume this one has the bug patched already?

 

No this will not work. 49LF flash series does not have all the addresses bits on their own dedicated pins. Again to interface it with the Xbox in Parallel Programming mode, you'd need additional logic to transfer the complete address in 2 parts(toggling R/C# pin).

The Xbox TSOP uses 29(L)F memory interfacing logic which does not work the way LPC flash chips works in PP mode. Check the datasheet for a 29(L)F chip and a 49LF to see how different you interface them. For example, you can check for MX29F080 and SST49LF040 devices. You will see that the 2 chips do not work the same way.

Finally, 49LF040 chip does not have the required bug. Only SST49LF020 does work on 1.0/1.1 (you can make it work on 1.2-1.5 by taping onto the LFRAME signal directly on the MCPX chip.).

Seriously, save yourself the trouble and install a LPC modchip like Aladdin XT or DuoX3.

 

One problem: there's NO original Xbox modchip in my town. I've searched and there's none. The only ones I found are for PS2,X360 and Wii.

And for the DIP32 mod,the only thing I'm missing is a old motherboard and a HDD and a new tip for my 40W soldering iron.No worries,that iron can do the job,I even used it to do the TSOP points successfully. I have 2 DIP32 chips though : MX 29F002NTPC and an Atmel AT49F002T.
And as a fact,Aladdin XT seems to use the fixed 49LF020A.

 

#1: www.aliexpress.com/item/subject/2012662721.html

#2: www.eurasia.nu/shop/product_info.php?cPath=47&products_id=266

You'll have to wait a week or two but your problem will be solved. You can also look on these forums if anyone is selling a modchip you could get faster.

 

Thanks for the link to Aliexpress. I was searching for an OG Xbox modchip for a while and this is the cheapest one I have seen, because the shipping costs aren't insane.

 

The price seems reasonable on Aliexpress as proarturs said (22 RON seems more than good for me) but I can't buy it since I'm broke right now,and very probably the price will rise. (Or not?Who knows.)

When I'll have some money I'll go ahead and buy it. Until then,I'll let my box bit the dust. (blank TSOP and it's a v1.4.)

The other box I have (a 1.1) is too damaged around the LPC header and has 2 - 3 missing caps,while the others are soldered back from some old crap PSU (HEC is written on them) along with some KY caps from 2 PS2 power supply so it's not even worth it. Not to mention that some traces to the TSOP are burnt. Anyway thanks for the links.